Mitigating the Urban Heat Island Effect in Megacity Tehran

Research ArticleMitigating the Urban Heat Island Effect in Megacity Tehran

Sahar Sodoudi1 Parisa Shahmohamadi2 Ken Vollack1 Ulrich Cubasch1 and A I Che-Ani3

1 Institut fur Meteorologie Freie Universitat Berlin Carl-Heinrich-Becker-Weg 6-10 12165 Berlin Germany2 Resilient Urban Planning + Development (RUPD) GbR Eichendorffstr 1 10115 Berlin Germany3Department of Architecture Faculty of Engineering and Built Environment University Kebangsaan Malaysia (UKM)43600 Bangi Selangor Malaysia

Correspondence should be addressed to Sahar Sodoudi sodoudizedatfu-berlinde

Received 1 May 2014 Revised 18 July 2014 Accepted 20 July 2014 Published 7 September 2014

Academic Editor Sultan Al-Yahyai

Copyright copy 2014 Sahar Sodoudi et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Cities demonstrate higher nocturnal temperatures than surrounding rural areas which is called ldquourban heat islandrdquo (UHI) effectClimate change projections also indicate increase in the frequency and intensity of heat waves which will intensify the UHI effectAs megacity Tehran is affected by severe heatwaves in summer this study investigates its UHI characteristics and suggests somefeasible mitigation strategies in order to reduce the air temperature and save energy Temperaturemonitoring in Tehran shows clearevidence of the occurrence of the UHI effect with a peak in July where the urban area is circa 6K warmer than the surroundingareasThemobile measurements show a park cool island of 6-7 K in 2 central parks which is also confirmed by satellite imagesTheeffectiveness of three UHI mitigation strategies high albedo material (HAM) greenery on the surface and on the roofs (VEG) anda combination of them (HYBRID) has been studied using simulation with the microscale model ENVI-met All three strategiesshow higher cooling effect in the daytime The average nocturnal cooling effect of VEG and HYBRID (092 110 K) is much higherthan HAM (016 K) although high-density trees show a negative effect on nocturnal cooling

1 Introduction

Tehran is Iranrsquos largest city with the highest rate of urban-ization This megacity has a large densely-populated area of750 km2 (8million people during the night-time) which has amajor impact onhumanwelfare (eg air andnoise pollution)Both the concentration and the mobility of the popula-tion along with diverse social factors have transformedthe infrastructure and spatial features of the metropolitanarea According to [1] urban development has directlyaffected Tehranrsquos urban structure which can be observed inthe metropolitan area Previous investigations of the urbangrowth processes of Tehran from 1554 onwards show thatthis city has undergone frequent transformations [2ndash7] As aneffect of weak urban management the rural population wasattracted to the urban areas and the growing urbanizationled to severe environmental changes (eg increasing barrenlands)

The urban development of metropolitan areas greatlyincreases urban environmental problems such as air pol-lution higher temperature traffic congestion and energyconsumption As witnessed in the Tehran metropolitan arearecent increases in the rate of urbanization deteriorate theurban environment One crucial problem of developingurban areas is that of rising temperature compared to ruralareas known as the urban heat island (UHI) Emmanuel [8]showed that the UHI is the accumulated warm air over thehigh density of built-up areas Asimakopoulos et al [9] statedthat the constructions in urban areas absorb heat during theday and re-emit it after sunset creating high temperaturedifferences between urban and rural areas According to Oke[10] the size and structure of the UHI vary in time and spacedue to meteorological conditions and urban characteristicsThere are various causes for the formation of the UHI in thecities The important factors causing the UHI are the highfraction of built-up areas (Buildings and pavements) as well

Hindawi Publishing CorporationAdvances in MeteorologyVolume 2014 Article ID 547974 19 pageshttpdxdoiorg1011552014547974

2 Advances in Meteorology

as the lack of vegetation The main reasons of the formationof the UHI are the low albedo and the high heat capacity ofbuilt-up surfaces such as concrete or asphalt which absorbhigh amount of the short-wave radiation during the day thisenergy is then slowly released during the night as long-waveradiation and leads to higher air temperature in the urbanareas Evapotranspiration describes the transfer of latent heatfrom the earthrsquos surface to the air via evaporating waterUrban areas tend to have less evapotranspiration relative tonatural landscapes because of the lack of vegetation Thisreduced moisture in built up areas leads to dry imperviousurban infrastructure reaching very high surface tempera-tures which contribute to higher air temperatures With adecreased amount of vegetation cities also lose the shadeand cooling effect of trees Therefore greenery and usinghigh albedo materials are two strategies which can mitigatethe UHI The location of city has direct impact on theformation of UHI Different locations within a given regionvary greatly in their temperature wind conditions humidityprecipitation fog and so forth Such variationsmay be causedby differences in distance from the sea altitude direction ofslopes and the general topography of the area [11] Wind andhumidity are two main variables which control the intensityof UHI The formation of UHI phenomenon depends uponthe size and density of the population Oke [12] has correlatedUHI intensity to the size of the urban population Theyhave a direct relationship in which with higher populationUHI intensity will be increased Buildings and the densityof built-up area modify the wind the radiative balance andthe temperature conditions near the ground level as built-up area have lower albedo and higher heat capacity com-paring to natural surfaces Therefore the fraction of built-up area is a relevant factor in formation of UHI [11] Urbangeometry can impede the release of long-wave radiation intothe atmosphere When buildings absorb incoming short-wave radiation they can re-radiate that energy as long-wave energy or heat However at night due to the denseinfrastructure in some developed areas that have low sky viewfactors urban areas cannot easily release long-wave radiationto the cooler open sky and this trapped heat contributes tothe urban heat island

UHI intensity is greatest under stationary high-pressuresystems in stable air and clear-sky condition It tends todisappear if cloudiness and wind speed increases The studyof Darand and Halabian [13] shows that a dominant strongridge at the upper level (850 hPa and 500 hPa Azores highpressure) which is associated with a thermal low pressureon the surface over Pakistan and Iran is the most frequentpattern from April until September in Tehran This system isaccompanied by cloudless sky and a stable boundary layerwhich leads to a higher intensity of UHI The ridge ofAzors high pressure in the upper level results in increasedconcentration of pollution when pollutants expand to theeast and are located over north part of Iran It blockedthe convection of surface air reducing vertical mixing andthereby increasing air pollutant concentrations near theground A subsidence is usually formed under the high-pressure systemsThe interactions between the low pressurescentered at the Pakistan to the north part of Iran with Azores

high pressure result in inversion occurrence in Tehran Thispattern is the most frequent and the associated concentrationof pollution is very high More frequent heatwaves and stressare projected over most regions of the densely-populatedurban areas for the next decades [14] Thus studying theUHI effect and mitigation strategies is one of the majorpriorities for planning the urban developments in megacitieslike Tehran

Greenery is a usefulmitigation strategy to reduce theUHIby cooling the air and providing shade and milder outdoorboundary conditions as well as better thermal comfort Manyresearchers have studied the effects of greenery such asgreen roofs [15ndash18] and high albedo materials [8 19ndash24] onreducing the local temperature and UHI intensity

Table 1 summarized the results of some studies on mit-igating of UHI in different cities As it shows differentUHI mitigation strategies have been applied Reroofing withlight colors and planting shade threes indicates the highestcooling effect among the other strategies (3 K) Applyingtrees with broad canopies within residential yards led also to24 K temperature reduction although other studies indicatea cooling effect between 05ndash16 K which show the highercooling effect of shade trees in comparison to planting groundlevel vegetation or using high albedo materials

The UHI has a direct impact on human health due tohigher temperature which is responsible for the morbidityand mortality risks Both the planning and policies for urbanenvironmental sustainability in the metropolitan area ofTehran are impossible without a temperature mitigation pol-icy Mesoscale air flows such as sea breezes mountain valleywinds (slope-winds) and the urban heat-island circulationspartly control the local weather and pollutant transportworldwide

Themain aim of this paper is to study the effects of green-ery in connection with the high albedo materials in reducingthe UHI effect in themetropolitan area of Tehran and findingamitigation policy for adapting the infrastructure against themicroclimate changes However there is a lack of researchin the context of Tehran UHI In this paper we have appliedsatellite data mobile measurements and permanent stationsin order to study the UHI of Tehran

The effect of greenery and high albedo materials on localclimate in the 6th district of Tehran has been simulated byusing themicroclimatemodel ENVI-met [33] for a typical hotsummer-day in Tehran The simulations were carried out forcurrent situations as well as under three different mitigationstrategies

2 Case Study Area

Tehran (35∘421015840N 51∘251015840E) the fastest growing city in Iranwith around 8 million inhabitants and an area of 750 km2 isone of the largest cities in the world located on the southernside of the Alborz mountain range and is limited to thehighlands and mountains in the North and East and to theflat plains and desert in the South and West (Figure 1) Theaverage annual rainfall is approximately 230mm with mostprecipitation falling in autumn and winter months Due to

Advances in Meteorology 3

Table 1 A review on maximum temperature in different cities UHI mitigation methods and their cooling effects as well as the percentageof energy saving of different UHI mitigation strategies in different regions Planting shade threes shows the highest cooling effect (3 K) in LosAngeles

Reference Method Maximumtemperature

Reduction intemperature Reported savings Cityregion

[19] Reroofing lighter colorsand planting shade trees mdash 3K 10 Los Angeles

[25] Replacing urban areaswith grass land

30∘C (surfacetemperature) 16 K mdash Hong Kong

[26]New park nearby

commercial area (1 kmdownwind)

403∘C (surface tempOf grass field) 15 K 15 Tokyo

[27] Reducing anthropogenicheat mdash 12 K 4ndash40 Tokyo

[28]Large scale increase insurface albedo andvegetative fraction

37∘C 05ndash15 K 10(at peaks) USA

[29] Building planting (wallsand roofs) 2895∘C (1m) 13 K 25

[30]Trees with broadcanopies withinresidential yards

32∘C 24K 124mio l Wateryear Phoenix

[30] Roofs with high albedoand vegetation 282∘C mdash 24 14 45 Barcelona Palermon

Cairo

[31] Low albedo buildinggeometryrarrwind effects 344∘C 07 K mdash Singapore

Table 2 An overview on climate data from the station Tehran-Mehrabad (MHR) 1980ndash2009

Annual mean temperature 175∘CAnnual mean precipitation 230mmAnnual mean humidity 40Annual most frequent wind direction WestMean number of clear days 318Mean number of inversion occurrences 251

high elevation aridity and latitude the city experiences fourseasons Climate can be extremely hot in the summer (withmidday temperatures ranging between 30 to 40∘C) and coldin winter when night time temperatures can be below thefreezing point Local precipitation is absent for 6 months ofthe year on the low lying areas Synoptic scale low pressuresystems that originate from the Mediterranean propagateover the region in spring and autumn while in winter thesouthward extension of the Siberian high pressure system canadvect cold temperatures over the Iranian Plateau A largescale easterly flow dominates the area in the summer thoughtto be associated with a circulation pattern named ldquothe windsof 120 daysrdquo caused by a thermal low over Pakistan [34]Therefore aside from the summer when large scale flow iseasterly a westerly direction is preferred at other times but isthought to be modified by the mountains Table 2 shows theannual mean temperature humidity precipitation and othervariables from 1980 to 2009 in the station Tehran-Mehrabad(MHR) Table 2 demonstrates the ideal condition for UHI

formation in Tehran (annualmean humidity of 40 318 cleardays per year)

Air pollution in Tehran is the biggest environmentalproblem and determined even by its geographic positionThe Alborz mountain range with an average width of about100 km [35] acts as an almost continuous wall The altitudeof Tehran is between 900 to 1700 meters above sea level[36] There is a major difference in altitude between thenorthern and southern parts of the citywhich has a significantimpact on the characteristics of urban spaces in the Tehranmetropolitan area In semiarid regions such as Tehranthe climatic conditions regularly lead to cloudless weatherconditionswithweakwindswhich can approximately be con-sidered ldquoidealrdquo as defined by Oke [37] This is especially trueduring summer when synoptic influences are reduced anddepression disturbances are less frequentThemeasurementsof Zawar-Reza et al [38] inTehran confirm the typical diurnalcycle of an unstable turbulent planetary boundary layerduring the day where downward momentum flux is highand hence wind speeds are increased Towards the eveninga stable boundary layer with decreased wind speeds developsand keeps on growing throughout the night due to long-waveradiative loss producing a sensible heat flux directed awayfrom the surface This is important as it emphasises the highpotential of a poorly ventilated nocturnal boundary layerthat contributes to urban heat island and elevated pollutionlevels

Several national studies have investigated trends in aver-ages of maximum and minimum temperature and precipita-tion in Iran Alijani [39] Jahadi Toroghi [40] and Rasooli[41] have previously worked on some selected stations


TehranStudy area

NE

SW 0 2 4 8 12 16

51∘3599840051∘3099840051∘2599840051∘2099840051∘1599840051∘1099840051∘5998400

51∘3599840051∘3099840051∘2599840051∘2099840051∘1599840051∘1099840051∘5998400

35∘55998400

35∘50998400

35∘45998400

35∘40998400

35∘35998400

35∘30998400

35∘55998400

35∘50998400

35∘45998400

35∘40998400

35∘35998400

35∘30998400

(km)

Figure 1 22 urban districts in mega city Tehran The dashed areashows the 6th urban district

Rahimzadeh and Asgari [42 43] using a set of high-qualityrecords showed significant trends for minimum and maxi-mum temperatures and precipitation overmost of the Iranianterritory for the period 1951ndash1997 They found increasingtrends in minimum temperature for all stations under studyexcept Oroomieh located in the northwest of the countryThe result for Oroomieh was confirmed by Pedram et al[44] In Iran the outcome of the global warming is theincreasing frequency of extreme events such as heat wavestorrential rains or prolonged intensive droughts henceincreasing danger and harm to the built environments andpeople Rahimzadeh and colleagues [45] examined extremetemperature and precipitation as indicative climatic variablesto determine recent climatic changes over Iran They presentthe results from 27 synoptic stations which have been qualitycontrolled and tested for homogeneity and have less missingdata For each station 27 indicative climatic indices werecalculated Marked negative trends for indices like frost days(FD) ice days (ID) cool days (TX10p) cool nights (TN10p)and diurnal temperature range (DTR) were found over mostregions of Iran Conversely positive trends were found forsummer days (SU25) warm days (TX90p) and tropicalnights (TR20) over most regions of the country For indicessuch as Cold Spell Duration Index (CSDI) and Warm SpellDuration Index (WSDI) both positive and negative trendswere obtained Another study on coastal regions in Iran [46]indicates that temperature indices are absolutely consistentwith warming Warm nights hot days and hot day and nightfrequencies increased while cold spell and cool day and nightfrequencies declined Tagavi and Mohammadi [47] have also

confirmed the decrease of frequency of cold and increase ofwarm events during the past years in Iran

The analysis of intensity and frequency of extreme eventsis a very important step in the process of planning anddesigning the urban areas especially in the semiarid climateof Iran In these areas climate is very fragile and a suddenchange may cause destructive outcomes [48] Beside themore frequent heat waves the rapid urbanization growth andthe related UHI will also lead to higher temperature in thefuture

In Tehran the change of land use from natural surfacesto new built structures during recent decades and expansionof the city size results in changes of the natural surface ofthe earth The changes of materials that cover the earthrsquossurface affect the absorption of solar energy and the changesof the shapes of the earthrsquos surface Moving the large numberof population from the suburbs to the fast growing Tehranurban area caused acceleration of urbanization increasingthe city size and the density of built-up area respectivelyIn Tehran the local winds are often not strong enough tocirculate the air Around 70 of the winds in Tehran havespeeds below 6 knots and have little impact on air circulationin large built-up areas Only 30 of the winds which usuallyblow in spring late summer and early autumn have speeds ofmore than 10 knots and can clear the air [49] The problemhowever is that the major winds blow from the west southand south-east where most of the industries are locatedRather than cleaning the air they can pollute the air furtherOnly the winds from the northern mountains with theirlimited impact blow in the right direction

The on-going climate change is predicted to yield a grow-ing number of extreme climate events which will increasein both intensity and frequency It will have a direct impacton population health morbidity andmortality Many studieshave previously shown that the elderly in a society are amongthe most vulnerable to heat waves [50] Over the past threedecades Tehran has experienced warmer summers and highamounts of heat-related mortality Ahmadnezhad et al [32]showed that the total excess mortality during the last 17heatwaves in Tehran which was about 89 deaths per heatperiod Figure 2 shows the average temperature maximumof all recorded heat waves in Tehran from 2001 to 2011Table 3 shows also the length of the each heat wave thenumber of death during its period as well as the excessmortality in percent [32] for five different categories (allmortality causes elderly people ge 65year cardiovascularcauses cerebrovascular causes and respiratory causes) AsFigure 2 shows during all heat waves the average maximumtemperature exceeds 38∘C in the whole period The largestdeath ratio (1005 death in 8 days) and also excess mortality(192) was occurred in 2009rsquo wave which was the hottestwave with the average ofmaximumdaily temperature of 40∘C(Table 3) Mortality for 65+ years had also significant excessmortality The largest number of deaths (65+) also happenedin heat wave of 2009 and was about 177 related to thetotal deaths of 558 The total number of death during allheat waves in the last decade was about 14475 which hasa mean value about 851 deaths per heat wave The peopleolder than 65 years are the most affected category by heat


Table 3 Heat waves in Tehran from 2001 to 2011 Em indicates the excess mortality in percent and NofD indicates the number of death from5 categories all mortality causes elderly people ge65 years with cardiovascular cerebrovascular and respiratory causes [32]

Year (number of heat waves) Length in days All causes gt65 years Cardiovascular Cerebrovascular RespiratoryEm () NofD NofD NofD NofD NofD

2001 (1) 4 61 452 240 181 49 182001 (2) 4 10 493 246 211 46 252001 (3) 3 116 327 157 143 18 132002 (1) 6 98 692 366 308 42 182002 (2) 7 116 524 275 204 35 182003 1 08 1704 873 721 164 752005 (1) 11 32 1377 744 504 129 1042005 (2) 5 146 658 370 238 64 382006 (1) 7 158 881 466 303 61 542006 (2) 5 39 587 319 203 48 392006 (3) 5 113 619 322 173 64 462006 (4) 5 117 885 468 293 77 602008 (1) 7 64 868 482 343 49 642008 (2) 3 56 392 208 147 24 402009 8 192 1005 558 401 73 762010 14 27 1658 939 613 109 1432011 11 89 1353 745 476 103 112

375

38

385

39

395

40

405

Aver

age m

axim

um te

mpe

ratu

re

Year and number of heat wave

2001

(1)

2001

(2)

2001

(3)

2002

(1)

2002

(2)

2003

2005

(1)

2005

(2)

2006

(1)

2006

(2)

2006

(3)

2006

(4)

2008

(1)

2008

(2)

2009

2010

2011

Figure 2 The average maximum temperature of heat waves inTehran from 2001 to 2011 The number in parentheses indicates theorder of the heat wave during the year As it has been shown threeheat waves affected Tehran in 2001

stress (53) People with cardiovascular problems are in thesecond place (37) although the percentage of death due tocerebrovascular and respiratory causes is under 10 Thusreducing the temperature through mitigating of the UHI isan important key for the urban and landscape planners inTehran in order to obtain better conditions of human comfortand human health

Although Tehran has 22 districts (Figure 1) the simu-lation of the effects of UHI mitigation strategies (greeneryand high albedo surface materials) on local climate for thewhole of Tehran is not possible due to the limitations of themicroclimate model ENVI-met As a result the 6th urbandistrict of Tehran was selected for simulations The selectionof this urban district is due to its location which is near the

Table 4 Fraction of impervious surface area and vegetation in the6th urban district in Tehran

Type of land use Percentage within 6thurban district Area (h)

Impervious surface area(pavement buildings) 9737 208752

Vegetation (tree canopy andground level vegetation) 24 5157

centre of Tehran and surrounded by the main urban axes ofthe city and its traffic congestion This urban district has thehighest concentration of important business centres whichare an important function of the city and is one of the mostpolluted districts in Tehran The topography of the districtwithNorth-South andEast-West slopes have led to the uniquediversity of the urban space and its features especially in thenorthern parts of the district which contributes to anunequaldistribution of pollution and provides a warm air canopy overthe central part The average administrative density of the6th urban district is about 103 persons per hectares With anarea of 2149 hectares the latter is about 35 of Tehranrsquos areaand had a population of 224097 people in 2006 which isalso about 3 of the cityrsquos population The main land uses ofthe zone included 349 residential 276 transport 224public welfare services 83 general activities 24 military24 vegetation and finally 088 urban utilities [51] Theaverage height of the buildings is usually less than that ofthe other large cities of the world (4-5 story building andthe mean sky view factor is about 05 [52] Table 4 shows thepercentage of impervious surface area and vegetation in the6th urban district [53]This district with around 98 percent ofbuilt-up area has no potential to act as a green environment


Karaj

Tehran

Mehrabad

Geophysics

(km)

45 50 55 60

26

28

30

32

34

36

38

40

Longitude

Latit

ude

1

23

3

45

6

6

7 8

9 10

0

1112

12

13

14

1516

1718

18

19

20

21

22

N

Figure 3 The location of Tehran and three meteorological stations Geophysics (GEO) Mehrabad (MHR) and Karaj

The roofs have a total area about 643 h and can be used asfree spaces to mitigate the UHI regarding different methodsGreenery constitutes 5157 h of this urban district whichindicates circa 221m2 of green space per capita althoughthe amount recommended by the United Nations is about20ndash25m2 [53] The average per capita green space within anurban area of 221m2 is very low compared with its average inother Asian cities such as 10m2 in Singapore 7m2 in Tokyoand 125m2 in Shanghai [54]

3 Methodology

In the first part of this study the characteristic of the UHI inTehran has been analyzed using measured 2m temperaturedata from synoptic stations and mobile measurements inurban and rural areas as well as the derived land-surfacetemperature from LandsatThe second part of the study dealswith UHI mitigation strategies (eg high albedo materialsand greening) The influence of high albedo materials andgreening on 2m temperature and the relative humidity ofthe 6th urban district of Tehran have been studied and theirapplication as mitigation strategies has been discussed

31 THE UHI Characteristic in Tehran All of the meteoro-logical data used for the UHI analysis were obtained fromthe Islamic Republic of Iran Meteorological Organization(IRIMO) The data include time series of daily mean maxi-mum andminimum 2m temperatures as well as the 3 hourlyvalues for three stations These stations (Figure 3) includeMHR (located at Mehrabad Airport representing the urbanstationwith an altitude of 11908m)GEO (located at TeheranGeophysics Institute representing another urban stationwithan altitude of 14186m) and KRJ (located at Agriculture

Institute in Karaj representing a rural station with an altitudeof 13125m) The average altitude of Tehran is 1200m withan 800m altitude difference between its lowest and highestpoints In this study two urban stations MEHR (lower thanrural station) and GEO (higher than rural station) have beenconsidered in order to show the effect of urbanization aswell as the station elevation of the air-temperature differencebetween urban and rural areas and thus no temperaturecorrection has been attemptedThe station TehranMehrabadhas the longest record from 1951 till 2008 The stationsKRJ and GEO were installed in 1985 and 1991 respectivelyThus the time range of 1991ndash2009 was determined for theinvestigating of the UHI due to the availability of the datafrom GEO

The stations used in the study are at different altitudesThe difference in minimum temperature serves as the pri-mary indicator of the UHI intensity because the difference isnormally most pronounced at night [55] Mehrabad station(MHR) is located in western part of Tehran where the airportis situated The Geophysics station (GEO) is located in the6th urban district and has been used to calibrate the mobileinstruments In Karaj station (KRJ) the major land use isagriculture AtMehrabad Geophysics andKaraj stations theannual maximum and minimum dry-bulb 2m temperaturesindicate a slow upward trend during the period 1991ndash2009(Figure 4)

It is clear that stations GEO and KRJ have very similarcharacteristics during the day which is shown as time-seriesof annual mean maximum temperatures The MHR stationwith a lower altitude of between 300 and 400m showsthe highest values It indicates that the important factor todetermine the daily temperature is the altitude differenceTheannual mean minimum temperature of these three stationshas also been shown in Figure 4The similarity between GEO


1991 1993 1995 1997 1999 2001 2003 2005 2007 200968

101214161820222426

Year

(∘C)

MHR-minKRJ-minGEO-min

MHR-maxKRJ-maxGEO-max

Figure 4 The annual mean maximum and minimum dry-bulb2m temperatures of stations GEOMHR and KRJ during the period1991ndash2009

and MHR is much more than between GEO and KRJ (urbanand rural) although they have only a circa 100mdifference inaltitude It indicates that the urbanization and built-up areasare important factors to determine the temperature at night(3-4 hours after sunset) As it has been shown in Table 2 thefrequency of occurrence of frontal systems and precipitationis about 12 In order to characterize the UHI we useonly the cloudless days without any precipitationfrontalpassage in the period of 1991ndash2009 when the UHI or urban-induced warming is the strongest [56] The investigationof a 19-year period of urban (MHR and GEO) and rural(KRJ) minimum temperatures in Tehran clearly shows thetemperature difference between these two areas (Figure 5)The largest UHI intensity was in the summer (July) ForMHR-KRJ and for GEO-KRJ July has a peak UHI value of58 and 61∘C respectively For both MHR-KRJ and GEO-KRJ the smallest UHIs exist in winter with minimum valuesin December 288 and 217∘C respectively The finding of astronger UHI in summer isin contradiction with Zhou andShepherdrsquos [57] and Kim and Baikrsquos [58] investigation of UHIin Atlanta and Seoul Zhou and Shepherd found the strongestUHI intensity in Atlanta in spring while Kim and Baik foundstronger UHIs in the winter and fall rather than the springHowever Kim and Baik did note that the trend in UHI overa 24-year period was greatest during the spring

The emergence of spring vegetation may result in alarger albedo gradient with the urban area which wouldcause a larger UHI According to Unger et al [59] theseasonal UHI pattern may be determined to a high degree byurban surface factors Cloudiness and wind speed may playa negative role in the development of UHI Liu et al [60]stated that the seasonal UHI variation tended to be negativelycorrelated with the seasonal variation of relative humidityand vapour pressure Tehran is located in the semiaridcontinental climate It has hot and dry summers and coldwinters The precipitation period is from November to Mayfollowed by a dry period from May to October with rare or

2

3

4

5

6

7

Janu

ary

February

March

April

May

June July

August

Septem

ber

Octob

er

Novem

ber

Decem

ber

(K)

MHR-KRJGEO-KRJ

Figure 5 The difference between minimum temperatures of sta-tionsMHR andGEO and the rural station KRJ in the period of 1991ndash2009

1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010

15155

16165

17175

18185

19195

20

Year

Tehran-MehrabadTrend

(∘C)

Figure 6 Mean annual 2m Temperature from 1951ndash2009 in TehranMehrabad station

little precipitation [61] The seasonal UHI pattern may beaffected by seasonal cloudiness in Tehran The analysis ofmean wind speed from 1953 to 2006 in the Tehran Mehrabadstation shows that in this period the percentage of calmwindincreased and led to a reduction of themean wind speed [62]Figure 6 shows the mean annual 2m temperature from 1951to 2009 in the Tehran Mehrabad station As has been shownthemean annual temperature increased in this 58 year periodThe red line shows the positive temperature trend The rapidincrease of 2m temperature in Tehran is due to the rapidgrowth of the population which led to an increase in built-upareas with low albedomaterials and reduced sky view factorsThe number of private cars (per 1000 people) changed from5 in the year 1956 to 90 in the year 2006 [62] Besides thisquick change in the number of cars being used the energyconsumption and resulting heat from new built-up areascaused the high concentration of air pollutants in Tehranwhich absorbs and reemits long-wave radiation and leads tostronger UHI A comparison between MehrabadGEO and


Karaj in terms of climatic changes and physical developmentover the period 1991ndash2008 reveals that the warming in theurban stations is strongly attributed to the increase in theUHIeffect

32 Satellite Images A satellite image was employed tomap out the surface temperature in Tehran to verify localboundaries of urban and rural areas and to identify hot spotsA Landsat 7 ETM+ satellite image obtained on 18 July 2000(due to limitations of the data in Tehran only this map wasavailable) with spatial resolution of 15m in panchromaticband 30m in 6 visible bands and 60m in thermal band wasselected which was provided by the Iranian Space AgencyThe image was radiometrically calibrated and geometricallycorrected to obtain the detected radiance data The detectedradiance in thermal band was converted to the equivalentsurface temperatures using Planckrsquos blackbody formula Landcover was classified into several classes using the visible NIRand SWIR bands Instead of ambient temperature the relativesurface temperature can be seen from the satellite imageWithin the urban canyon canopy layer in the morning orwhere wind velocity is low the surface temperature is deter-mined by adjacent surfaces Thus the surface temperaturemap is acceptable for studying the UHI effect in the earlypart of the day The reason for using the satellite images is toacquire the urban-rural visual difference at mesoscale ratherthan to provide absolute values Time limitations and the lackof a traverse observational approach to ascertain the UHIintensity limit the use of satellite imagery for exploring UHIThus in order to trace the gradual influence of urbanizationon local climate historical weather data were examined

Figure 7 shows the first observation of the clear surfacetemperature boundary that coincides with land use in Tehranand Urban District 6 The warm regions represented by thered and yellow colours are mostly located in the centralwestern and southern parts of Tehran where the centralbusiness district (CBD) industrial area(s) and airport arelocated respectively On the other hand the northern parts ofTehran are relatively cool shown in green This is due to theconcentration of greenery and water bodies as well as havingless impact from the high-density urban developments Thecontrast betweenurban and rural areas hints at the prevalenceof the UHI effect in Tehran although the satellite image onlyprovides the instantaneous observation during the daytime

The surface temperature of study area (Urban District6) reveals some areas with either high or low surfacetemperature In Figure 7 Region 1 experiences the highesttemperature during the daytime especially in the north andwest parts of the regionmainly because of the lack of extensivelandscape and because it is close to the two main highways(Hemat in the north and Chamran in the west) Similarlyhigher temperatures are observed in the east and northeastparts of Region 2 This is also reasonable since the exposedrunway absorbs a lot of incident solar radiation during thedaytime and incurs high surface temperature It might bedue to the bus station terminal located nearby Regions 5and 6 are close to the central business district of Tehranand neighbour with the Enghelab Street the most crowded

TehranStudy area

NE

SW 0 15 3 6 9 12

51∘3099840051∘2099840051∘10998400

51∘3099840051∘2099840051∘10998400

35∘50998400

35∘50998400

35∘40998400

35∘30998400

(km)

Surfa

ce te

mpe

ratu

re (∘

C)

High

Low

Figure 7 Land surface temperature from Landsat on July 18th2000

street In Regions 2 and 5 the effects of two parks (Saai andLaleh) on surface temperature can be observed (park coolisland PCI) The worst scenarios occur in some parts innortheast and northwest of the district The satellite imageshows a broad picture of temperature variance between urbanand rural areas This indicates the occurrence of UHI effectduring daytime in TehranThe hot spots are observed on hardsurfaces in the urban context since hard surfaces absorb lotsof solar radiation and cause high surface temperatures whichcontribute to the increase in the ambient temperatures

33 Mobile Measurements The 3 hourly meteorological dataderived from the local weather station network can remedythe temporal limitation of the satellite images but due tothe low number of stations in the urban area it is difficultto recognize the spatial distribution of 2m temperatureespecially the 2m temperature difference between differentpoints which are located in parks and green areas as well aswithin or between residential developments As a result fieldsurvey was carried out in order to complete the observationsderived from the satellite image and the weather stationsThe field survey was done by persons holding the mobilemeasuring instrument ldquoLutron LM-800rdquo at 31 designatedlocations 2m above the ground throughout the 6th urbandistrict of Tehran on a hot summer day 18 July 2009 Thisprofessional measuring instrument has a tiny bone shape andis lightweight small in size and is suitable for handling withone hand The instrument has a resolution of 01∘C and theaccuracy of plusmn(1 rdg + 1∘C)

Before starting measurement the instruments were cal-ibrated against the weather station ldquoGeophysicsrdquo which islocated in the 6th urban district The measurements were


(a) (b)

Figure 8 Mobile measurement in 6th urban district on July 18th 2000 (a) 1300ndash1500 h (b) 2100ndash2300 h

carried out by 3 persons every 5 minutes The measure-ments covered different land uses such as parks residentialcommercial and industrial areas and public services Theywere taken simultaneously at all locations in two sessionsthe day session between 1300 and 1500 h local time and thenight session between 2100 and 2300 h For every particularpoint the temperature was calculated by averaging threemeasurements in the same point It should be noted thatduring the measurements the instruments were shaded

The temperature distribution at various locations dur-ing the night- and day-times is shown in Figure 8 Thehighest temperatures were observed mainly in industrialand commercial land uses in the south of the district Theindustrial land uses generally have low-rise buildings andthe high temperature recorded in these areas is related tothe extensive usage of low albedo material in the buildingsThe high temperature of commercial buildings is related tothe use of concrete and dark stone which absorb most ofthe solar radiation and later release it into the atmosphereA maximum daily temperature of 426∘C was observed atthe industrial land use located in Enghelab Street The otherareas which had high temperatures (40ndash426∘C) includedmainly the west east and north borders of the districtwhere the main highways (Chamran Modares and Hemat)are located with high traffic congestion air pollution andthe lack of vegetation cover The lowest temperatures of301∘C and 31∘C were observed in the Saai and Laleh parks(park cool island PCI) The central part (high density built-up area) showed lower temperatures than the borders ofthe district Smaller sky view factor in this region leads tocooler temperatures than the border area The night-timetemperatures varied between 231∘C and 318∘C and it wasfound that the central part of the district was around 6-7∘C hotter than the other locations with greenery This alsoindicates the centre of the nocturnal UHI which has shiftedfrom the borders during the daytime to the central area Thehigh density of buildings and air conditions (anthropogenicheat) in this area leads to higher nocturnal temperaturesThe

average temperature of 242∘C was recorded in Laleh Parkthe large green area located in this district The maximumtemperature of 3182∘C was still noted in industrial land usein Enghelab Street The results of the field survey shows clearevidence of higher temperatures in the city centre than inthe green areas in 6th urban district of Tehran with thehigh density residential commercial and industrial land usesshowing around 6-7∘C higher temperatures

4 Numerical Modelling with ENVI-Met

ENVI-met [33] a three-dimensional numerical model wasemployed to study the basic pattern of the urban effects onmicroclimatic factors such as temperature wind speed andhumidity in the current situation of the 6th district of Tehranas well as under some UHI mitigation strategies ENVI-met is a tool for studying the surface-plant-air interaction atmicroscale We applied the 39928 version to simulate themicroclimate in this study A user-specified area input filedefining the three-dimensional geometry of the investigatedarea is required for each ENVI-met simulation It includesgeocoded building dimensions (eg width and height) soil(eg type and texture) surface (eg concrete or asphalt)and vegetation types The numerical model simulates aero-dynamics thermodynamics and the radiation balance incomplex urban structures It is designed for microscalewith a typical horizontal resolution from 05 to 10m anda typical time-frame of 24 to 48 hours with a time step of1 to 10 secs This resolution allows small-scale interactionsbetween individual buildings surfaces and plants to beanalyzed Typical domains are between a single street canyonup to a few hundred meters The model is designed formicroscale modeling due to the domainrsquos and the modelrsquostime limitations Despite these limitations ENVI-met hasbeen widely applied in different studies on UHI mitigationwhich demonstrates themodelrsquos capability Ng and colleagues[54] used ENVI-met to estimate the cooling effects of green-ing in a densely built-up area in Hong Kong They found out


Figure 9 The location of study area in Tehran 6th urban district

that roof greening was ineffective for human thermal comfortnear the ground due to the high building-height-to-street-width (HW) They also found out that the amount of treeplanting needed to lower pedestrian-level air temperatureby around 1∘C was approximately 33 per cent of the urbanarea Another study investigated the effect of xeriscaping onnear-surface temperatures and outdoor thermal comfort fortwo different areas in Phoenix [63] Xerophytic trees havestrong UHI mitigation potential in existing xeric residentialareas in Phoenix with greater cooling at microscales (25∘C)versus local scales (11∘C) and during nocturnal (0500) versusdaytime periods (1700) Yang et al [64] evaluated ENVI-met with field data in terms of the thermal behavior ofdifferent types of ground surface The results show thatthe model is capable of reasonably modeling the diurnalthermal behavior of different ground surfaces and theireffect on air temperature and humidity The simulated airtemperature and humidity were generally consistent with theobservations

5 UHI Mitigation Strategies and Results

A densely built-up area in ldquourban district 6rdquo with higher UHIintensity as shown in Figure 6 was selected for simulation(Figure 9) The model area has a size of 230m times 234mresulting in 94 times 92 times 25 cells with a resolution of 2m Theselected area has a dense residential building morphologyquite common in Tehran with an average height of 25mThegeographic co-ordinates of the model area were set to 3573∘latitude and 5150∘ longitude

ENVI-met simulations also require a configuration filecontaining local soil meteorological and building input data

for model initialization in the study area These include 2mtemperature and relative humidity 10m wind direction andspeed specific humidity at 2500m soil temperature andrelative humidity building interior temperatures thermalconductivity divided by mean wall or roof-width mean heattransmission and mean albedo for walls and roofs Thesedata were obtained from the measured data at Geophysicsstation (GEO) which is located near the study area andfrom the mobile measurements respectively Based uponthe preliminary analyses of temperature wind and relativehumidity obtained from GEO a clear hot day (18 July 2009)was selected for the simulation On this day the measureddata from GEO showed a maximum temperature of 384∘Cand a minimum of 292∘C the mean 2m temperature was338∘C with clear sky presenting 12 hours of sunshine Themeasured wind data confirmed the calm wind (16ms)from West The relative humidity was 35 percent whichis typical for a semiarid urban area such as Tehran insummerThe building information was obtained from typicalthermophysical properties of typical building materials inthis part of the 6th district

In order to study the UHI the simulations of 1500 h(approximate maximum temperature timing) and 0300 h(approximate minimum temperature timing) local time wereselected for the analysis The model was simulated for 48 hstarting at 6 am on July 17th and ending at 3 am on July 19thThis is because the best time to start is at sunrise and the totalruntime should be longer than 6 hours in order to overcomethe influence of the initialization and allow the model to spinup The weather parameters on July 17th were very similarto 18 July 2009 The main difference is 05K higher mini-mum temperature and 02K higher maximum temperature


CS HAM

VEG HYBRID

Figure 10 The current situation of the study area (CS) as well as with consideration of three mentioned UHI mitigation strategies HAMhigh albedo materials VEG greenery HYBRID HAM+VEG

The ENVI-met model was run for the simulation of thecurrent situation (CS) of ldquourban district 6rdquo of Tehran as wellas for three UHI mitigation scenarios

Using ENVI-met 3 different UHI mitigation strategieswere applied and their cooling effects and feasibility arediscussed as follows

(i) Scenario 1 change current low albedo materials tohigh albedo materials (HAM)

(ii) Scenario 2 cover the model area with greenery(vegetation and green roofs VEG)

(iii) Scenario 3 cover the model area with greenery alongwith high albedo materials (HYBRID)

Figure 10 shows the current situation of the investigatedarea (CS) as well as consideration of the three above-mentioned UHI mitigation strategies Greenery and vege-tation reduced solar radiation and lowered near-surface airtemperature due to evapotranspiration and shading and ledto better thermal comfort conditions Due to the alreadymentioned facts that greenery is the most widely appliedmitigationmeasure which could achieve huge energy-savingthrough temperature reduction in urban areas [65 66] ithas been applied in this study Changing the albedo ofroofs facades and pavements is the other applied mitigationmethod in this study which is more feasible due to thewater shortage in some summers in TehranThe last scenario(Hybrid) combines the effect of high albedo materials andgreenery (green roofs and more vegetation)

The current material used in buildings in the investigatedarea is concrete with an albedo of 030 the material of roofsand roads are asphalt with an albedo of 014ndash016 and some

parts of the study area are covered by soil with an albedoof 017ndash023 There is a lack of vegetation cover in this area(part of vegetation of whole model area 1815) In the firstscenario low albedo materials were changed to high albedoones asphalt to bright asphalt with albedo of 055 concretewas covered with white coating with albedo of 085 and soilwas changed to light coloured soil with an albedo of 06Usinghigh albedo materials reduces the amount of incoming solarradiation absorbed through building envelopes and urbanstructures and thus keeps their surfaces cooler The firstscenario was selected because of the high value of sunshineduration in Tehran In the second scenario 4344 of thesimulated area is covered by vegetation (grass and shade treeswith middle density canopies with a Leaf Area Index (LAI) of2) Aroung each building is covered by shrubs (Buxus hyrcanahedges) Due to the fact that the cooling effect depends onthe size of the vegetated area each free cell in the study areahas been covered by vegetation (grass) in order to obtainthe maximum potential cooling effect The vegetation on theroofs is considered as grass and shrubsThe simulation is onlyfor summer therefore no perennial plant has been consideredfor the simulation

In the third scenario (HYBRID) the first two UHImitigation scenarios were combined

Figure 11 shows the 2m potential temperature distri-bution in the study area in the current situation (CS) ona hot summer day (July 18) at 1500 and at 0300 h localtime respectively As has been shown maximum temper-ature in the current situation (circa 39∘C) occurs in roadswith low albedo materials (asphalt) and the areas with lessgreenery located in the west and southwest of the area at1500 h The simulation results show that in green areas


CS18072009-1500 [LT]

0 50 100 150

0

50

100

150

x (m)0 50 100 150

x (m)

y(m

)

CS19072009-0300 [LT]

25 30 35 25 30 35

2m potential temperature (∘C) 2m potential temperature (∘C)

Figure 11 2m potential temperature distribution in the study area in current situation (CS) on a hot summer day (July 18th) at 1500 and0300 h local time

(the points represent the trees) lower temperatures (circa34∘C) were observed The residential area also shows a lowertemperature due to shading and the higher albedo of thepavement The maximum temperature decreased from 39∘Cat 1500 h to 275∘C at 0300 h and occurred in the easternpart of the site in the current situation at 0300 h due to thewind advection from the west It shows that advection andnear-surface turbulence can influence the spatial distributionof 2m temperature in this area and so the microscalewarming or cooling effect can be expanded and reaches thesurrounding area

Figure 12 shows the 2m potential temperature differencebetween CS and each UHI mitigation scenario at 1500 and0300 h respectively In the first scenario (HAM) the coolingeffect of high albedo materials can be seen especially in thebuilt-up area and over the roads at 1500 h In comparisonwith the current situation the temperature was decreasedbetween 03 and 08 K in the built-up area due to reflectedincoming solar radiation The temperature reduction ishigher over roads which had an albedo increase of about04 (asphalt to bright asphalt) and in the current situationshowed the maximum temperature In addition maximumand minimum temperatures decreased by 07 and 142 Krespectively

At 0300 h built-up areas started to cool slowly andin comparison with the current situation the temperaturedecreased by 03 and 06 K In addition the middle part ofthe site (the residential area) was cooler than other partswhen compared to current situation It is clearly due to higheralbedo change in this part (circa 055)

When greeneries (green roofsmore vegetated areas withmiddle density canopy trees) were added in the secondscenario (Figure 11 VEG-CS) the temperature of urban areaswas reduced by about 2-3 K in daytime (1500 h) While thegreenery decreased the temperature due to shading (in caseof trees) and evapotranspiration (in the case of all vegetationtypes) there was still higher temperature on the roads Greenroofs and Buxus hyrcana hedges contributed to decrease thetemperature in the housing areas (local effect) by about 28 Kat 1500 h which is similar to the cooling effect of middledensity canopy trees in the northeastern part of study area inthe daytime The reduction of the air temperature in the areaby more vegetation cover is smaller at night-time comparedto daytime Although the trees in consideration have amiddledensity canopy with a LAI of 2 they reduce the long waveradiation loss due to the smaller sky view factor and areresponsible for a lower rate of cooling in the night-time Thetemperature reduction in the housing area can reach 370K atnight-time which is in agreementline with the other studies[25 26] In this scenario all free spaces including roofs arecovered by vegetation in order to estimate the maximumcooling effect of vegetation for a typical hot summer day ina semiarid climate

In the third scenario (HYBRID) the combination ofgreenery and high albedo material was examined in orderto test how these two strategies together can affect the nearsurface potential temperature (Figure 11 HYBRID-CS) Thetemperature was reduced up to 42 K in this case The resultsshow that HYBRID strategy leads to an overall cooling inthe whole study area at 1500 h while the cooling is focused


HAM-CS18072009-1500 [LT]

0

50

100

150

y(m

)

0

50

100

150

y(m

)

0

50

100

150

y(m

)

VEG-CS18072009-1500 [LT]

HYBRID-CS18072009-1500 [LT]

0 50 100 150

x (m)

minus4 minus2 0 2 4

HAM-CS19072009-0300 [LT]

VEG-CS19072009-0300 [LT]

HYBRID-CS19072009-0300 [LT]

0 50 100 150

x (m)

minus4 minus2 0 2 4

Difference 2m potential temperature (K) Difference 2m potential temperature (K)

Figure 12 Potential temperature difference between CS and each UHI mitigation scenario at 1500 and 0300 h local time


Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)

Figure 13 2m potential temperature time series simulated byENVI-met from 0800 July 18th 2009 till 0300 19th 2009 for thecurrent situation as well as under consideration of three mentionedUHI mitigation strategies

in the middle part at 0300 h Figure 11 shows that the parkcool island intensity is higher in the daytime than in thenight-time It is due to the radiation trapped in the northernpark where middle density canopy trees are packed and leadto a reduction of long-wave radiation loss during the nightThe first and second scenarios also contribute to reduce thetemperature singly while the third scenario makes a strongcontribution to reduce the ambient temperature

Figure 13 shows the 2m potential temperature time seriessimulated by ENVI-met from 0800 July 18 2009 till 030019 2009 for the current situation as well as taking the threeabove-mentioned UHI mitigation strategies into considera-tion In this figure the mean value over the whole simulatedarea is plottedThe results show that themean temperature inthe current situation is under-estimated by ENVI-met As hasbeen mentioned the minimum and maximum temperaturesof the Geophysics station which is near the study areawere recorded at 294∘C and 384∘C although Figure 12shows a maximum of 24∘C and a minimum of 355∘C inthe current situation The cooling effect of scenario HAMis effective only from 1200 to 1500 h (about 05 K) after1500 h there was no effective cooling The VEG scenarioshows a cooling of about 1∘C on average which decreases inthe night-time The HYBRID scenario had the same shapeas the last two scenarios but it leads to greater cooling(on average 15 K) with a maximum in the daytime As theFigure 12 demonstrates the last two scenarios can bring aboutnocturnal cooling and can mitigate the UHI effect

In order to understand the local effect of trees and bushesas well as higher albedo buildings and pavements threedifferent points in the study area have been selected and theirtemperature time series plotted Figure 14 shows the location

1

2

3

Figure 14 The location of three different points in the study area

Point 1

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)

Figure 15 2m potential temperature time series at Point 1

of these three points in the study areaThefirst point is locatedon the sidewalk between two buildings in the residential areaPoint 2 is located in the northern park and Point 3 is locatedin a low-density build-up area surrounded by some trees

Figure 15 shows the 2m potential temperature time seriesof Point 1 Although the point is located in the densely built-up area changing the albedo has little cooling effect with aminimum at night-time The VEG and HYBRID scenarioshave a much greater cooling effect especially after 2000 hThe maximum cooling is at 0300 h with a value more than2K with the HYBRID scenario The temperature time seriesof Point 2 is shown in Figure 16 The HAM scenario showsno influence on the 2m potential temperature A significantsimilarity can be seen between the temperature time seriesunder the VEG and HYBRID scenarios They both show amaximum cooling of 18 K between 1500ndash1700 then coolingstrongly decreases and shows a value of 03 K at 0300 h whatis due to the dense trees in the northern park which trap theheat due to the smaller sky view factor

Figure 17 shows the temperature time series of Point 3It is quite similar to the time series of Point 1 The single


Point 2

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)


Point 3

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)


difference is the smaller nocturnal cooling under VEG andHYBRID scenarios at Point 3 which shows the positive effectof greenery in the residential area where Point 1 is located

As Figure 18 shows relative humidity of 3527 percentwas observed in the built-up area of the current situation indaytime while it increased by between 3 and 5 percent in thelast two scenarios (shown only for VEG) Evapotranspirationin the northern park brings about an increase in the dewpointtemperature and raises the relative humidity It also increased

between 7 and 9 percent when the last two scenarios are takeninto consideration in comparison with the current situationat night-time (not shown) This increase in relative humidityleads to better human comfort conditions (optimal level40ndash60)The vegetation reduced wind speed in the secondand third scenarios is due to the tree density in the northernpart In the cross-comparison of the three scenarios for windspeed the wind speed became high in the first scenario withno vegetation Higher wind speed zones appear in the streetcanyon due to the channel effect from the two sides of theblocks

The ENVI-met simulation supported the data generatedfrom fieldmeasurement It indicates that greenery along withhigh albedo material has a significant cooling effect of upto 42 K on the surroundings during both day- and night-time which can save a huge amount of energy which isnormally used for air conditioning In addition ENVI-metsimulation shows that the lack of greenery and materialswith high albedo may cause bad thermal condition (highertemperature and lower relative humidity) especially in urbanareas with hard and low albedo surfaces Wind strength anddirection can affect the size of the cooled area around a greenspace which has to be investigated in further studies usingmesoscale models Due to the limitation of ENVI-met it wasnot possible to simulate the whole of Tehran

6 Discussion and Conclusion

This study has investigated theUHI characteristic inmegacityTehran and suggested some mitigation strategies regard-ing their feasibility Population growth the increase in thenumber of cars energy consumption and the resulting heatfrom new built-up areas have all caused stronger UHI anda high concentration of air pollutants in Tehran The largestUHI intensity was recorded in summer (July) with a meanvalue of 61 K over 19 years (1991ndash2009) and the smallest onewas recorded in winter with an average minimum value inDecember about 217 K A Landsat 7 ETM+ satellite imagefrom a hot summer day was employed to map the surfacetemperature in Tehran to identify hot spots For the studya high density built-up district with low albedo materialswas selected (Urban District 6) Mobile temperature mea-surement in this area in 2 time sessions (1300ndash1500 h and2100ndash2300 h) on a typical hot day (18 July 2009) was carriedout Amaximumdaily temperature of 426∘Cwas observed atindustrial land use located in Enghelab Street and the lowestone (301∘C) was observed in the Saai and Laleh parks whichshows the local effect of low albedo materials and greeneryon the temperature The mobile measurement shows highertemperatures compared to the permanent stationGEO in thisdistrict The results of the field survey shows clear evidenceof higher temperatures in the middle part when compared tothe green areas in 6thurban district of Tehran with the highdensity residential commercial and industrial land use areasshowing a higher temperature of circa 6-7 K

In the last part three different UHI mitigation strategies(high albedo materials green roofs and vegetation andhybrid) were simulated for a high density built-up area in the


CS18072009-1500 [LT]

0

50

100

150

0 50 100 150

x (m)

y(m

)

24 26 28 30

2m relative humidity ()

(a)

0 50 100 150

x (m)

VEG-CS18072009-1500 [LT]

minus6 minus4 minus2 0 2 4 6

Difference 2m relative humidity ()

(b)

Figure 18 2m relative humidity on July 18th 2009 (a) in current situation and (b) its difference from the case under VEG scenario

6th urban district of Tehran The key result from this studyis the estimation of the cooling potential of these strategiesas UHI mitigation methods especially in residential areas inthemegacity of Tehran on a hot summer day (18 July 18 2009)The results from the ENVI-met simulations presented in thisstudy clearly show that using high albedo materials (HAM)leads to a cooling of 05 K in daytime (1500 h) althoughit is much lower (016 K) in the night-time (0300 h) So itbrings only slight cooling in residential area during the nightand cannot be considered as an effective mitigation strategyalthough due to the high number of hours of sunshine perday in Tehran reduction in the heat storage of sunlit surfacesseems to be important White roof coatings could also beapplied over asphalt shingles When first applied these canprovide an albedo up to 08 which means that only 20 percent of the sunrsquos energy is being absorbed as heat which leadsto higher cooling compared to our results However theydo become dirty due to critical air pollution in Tehran andafter a short time their reflectance may be reduced to about05

In the second scenario (VEG) all free spaces withinthe studyndashincluding roofsndashare covered by vegetation (grassBuxus hyrcana and trees with middle density canopy) inorder to obtain maximal cooling which is generated onlyby vegetation The results show that the average cooling forthe whole area is about 113 K at 1500 and 092K at 0300 hThe nocturnal temperature decreased by about 2 K in theresidential area which is much greater than the slight coolingin the northern park The results of this scenario confirmedthe results of Ng [41] which demonstrated that green areasshould constitute at least 33 per cent of the urban area to lower

the temperature by about 1∘C In our case the greenery coversabout 43 percent of the whole area

The third scenario combines the last two scenarios(HYBRID) and shows the greatest cooling The averagecooling of this scenario is about 167 K at 1500 h and 110 K at0300 h although the maximum cooling is about 42 K in thegreen area between the buildings in daytime and night-timerespectively

This paper demonstrates the influence of greenery com-pared to high albedo materials in order to mitigate the urbanheat island intensity in megacity Tehran As is shown thelast two scenarios give promising insights into the benefitsof urban green planning Developing green spaces reducesthe air pollution and filters the particulate matter on theone hand and reduces the near-surface air temperature andprevents the overheating of sunlit surfaces on the otherAlthough the effect of 25m green roofs on the 2m temper-ature is smaller than the effect of surface greenery their airpollution filtering potentials are the same If regular irrigationis applied then evapotranspiration should also be taken intoaccount although due to the lack of water in the soil in hotsummer the evapotranspiration rate is low in Tehran Treesalso present some disadvantagesThey reduce the wind speedand lead to trap heat and humidity inside the urban canopylayer which causes warmer nocturnal temperatures as wellas cooler daily temperatures when compared to free spaceswithout vegetation as has been shown for the Point 2 whichis located in the northern park

Tehran is a part of a semiarid region in the world andhas encountered acute crises due both to the increase inthe population and the corresponding increase in the need


of water resources The per capita water consumption ratefor Tehran was more than 300 litres per day in 2007 whichis twice the international and even national level [67] Thisshortage is due to the low annual precipitation (ca 230mm[34]) as well as low available water resources Due to thislack of water especially during summers in Tehran thefeasibility of the mentioned UHI mitigation strategies (egthe irrigation of green roofs by treated waste water) shouldbe considered and discussed by stakeholders

Akbari found that peak energy demand in the USA risescirca 2ndash4 per cent for every 1 K increase in maximum airtemperature [68]This means that if we are able to reduce themaximum temperature by about 2-3K (by cooling residentialareas with the VEG and HYBRID scenarios) then we canreduce energy consumption by about 5ndash10 per cent whichwould be a huge saving in energy and would also lead tobetter conditions of human comfort and serve to offset globalwarming

It should be further noted that due to the limitation ofENVI-met it is not possible to make the simulation for thewhole city in order to investigate the size of the area whichwould be affected by the increased cooling although themesoscale models are able to simulate it but due to lowerresolution are not able to show the localised or microscaleimpact of the vegetation for example the effect of bushesor trees near buildings Coupling meso- microscale modelcould be useful to investigate the potential cooling effect ofdifferent strategies on different scales of climate change underconsideration

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The financial support of the Ministry of Education andResearch in Germany as well as German Academic ExchangeService (DAAD) within the frame of the project ldquoYoungCities-Developing Energy-Efficient Urban Fabric in theTehran-Karaj Regionrdquo is gratefully acknowledged Authorsalso acknowledge IR of Iran Meteorological Organization forproviding the data Authors are grateful to Dr Ahmadnezhadfrom the department of Epidemiology and Biostatistics ofTehran University for providing the mortality data

References

[1] A Madanipour ldquoUrban planning and development in TehranrdquoCities vol 23 no 6 pp 433ndash438 2006

[2] Z Fanni ldquoCities and urbanization in Iran after the Islamicrevolutionrdquo Cities vol 23 no 6 pp 407ndash411 2006

[3] AMadanipour TehranTheMaking of aMetropolis JohnWileyamp Sons London UK 1998

[4] E Ehlers and W Floor ldquoUrban change in Iran 1920ndash1941rdquoIranian Studies vol 26 no 3-4 pp 251ndash275 1993

[5] M Semsar Tehran Eine Stadtgeographische Studie SpringerVienna Austria 1986

[6] N Najmi Iran-e Ghadim va Tehran-e Ghadim JanzadehTehran Iran 1984

[7] A Farmanfarmaian and V Gruen ldquoTarh-e Jame-e TehranTehranrdquo Sazman-e Barnameh va Budgeh Tehran Iran 1968

[8] M R Emmanuel An Urban Approach to Climate-SensitiveDesign Strategies for the Tropics Spon Press London UK 2005

[9] D N Asimakopoulos V D Assimakopoulos N Chrisomalli-dou et al Energy and Climate in the Urban Built EnvironmentJames amp James Publication London UK 2001

[10] T R Oke ldquoTowards better scientific communication in urbanclimaterdquo Theoretical and Applied Climatology vol 84 no 1ndash3pp 179ndash190 2006

[11] B GivoniClimate Considerations in Building andUrbanDesignJohn Wiley amp Sons Toronto Canada 1998

[12] T R Oke ldquoThe energetic basis of the urban heat islandrdquoQuarterly Journal of the Royal Meteorological Society vol 108no 455 pp 1ndash24 1982

[13] MDarand andAHalabian ldquoClassification synoptic circulationpatterns impacting on air pollution in Tehranrdquo Journal ofApplied Sciences Research vol 3 no 5 pp 140ndash146 2013

[14] IPCC Climate Change 2007 The Physical Science Basis Con-tribution of Working Group I to the Fourth Assessment Reportof the Intergovernmental Panel on Climate Change CambridgeUniversity Press 2007

[15] N H Wong and Y Chen Tropical Urban Heat Islands ClimateBuildings and Greenery Taylor amp Francis London UK 2009

[16] H Akbari L S Rose and H Taha ldquoAnalyzing the land coverof an urban environment using high-resolution orthophotosrdquoLandscape and Urban Planning vol 63 no 1 pp 1ndash14 2003

[17] A Niachou K Papakonstantinou M Santamouris A Tsan-grassoulis and G Mihalakakou ldquoAnalysis of the green roofthermal properties and investigation of its energy performancerdquoEnergy and Buildings vol 33 no 7 pp 719ndash729 2001

[18] E G McPherson D J Nowak and R A Rowntree ldquoChicagorsquosurban forest ecosystem results of the Chicago urban forestclimate projectrdquo Tech Rep NE-186 Forest Service US Depart-ment of Agriculture 1994

[19] A H Rosenfeld H Akbari J J Romm and M PomerantzldquoCool communities strategies for heat island mitigation andsmog reductionrdquo Energy and Buildings vol 28 no 1 pp 51ndash621998

[20] T Asaeda V T Ca andAWake ldquoHeat storage of pavement andits effect on the lower atmosphererdquo Atmospheric Environmentvol 30 no 3 pp 413ndash427 1996

[21] H Taha ldquoUrban climates and heat islands albedo evapotran-spiration and anthropogenic heatrdquo Energy and Buildings vol25 no 2 pp 99ndash103 1997

[22] H Akbari S Davis S Dosano J Huang and S WinnettCooling Our Communities A Guidebook on Tree Planting andLight-Colored Surfacing United States Environmental Protec-tion Agency Washington DC USA 1992

[23] T R Oke G T Johnson D G Steyn and I D WatsonldquoSimulation of surface urban heat islands under ldquoidealrdquo condi-tions at night part 2 diagnosis of causationrdquo Boundary-LayerMeteorology vol 56 no 4 pp 339ndash358 1991

[24] E I Griggs T R Sharp and J M MacDonald ldquoGuide forestimating differences in building heating and cooling energydue to changes in solar reflectance of a low-sloped roofrdquo OakRidge National Laboratory Report ORNL-6527 1989

[25] H Tong A Walton J Sang and J C L Chan ldquoNumericalsimulation of the urban boundary layer over the complex


terrain of Hong Kongrdquo Atmospheric Environment vol 39 no19 pp 3549ndash3563 2005

[26] T V Ca T Asaeda and E M Abu ldquoReductions in airconditioning energy caused by a nearby parkrdquo Energy andBuildings vol 29 no 1 pp 83ndash92 1998

[27] Y Kikegawa Y Genchi H Kondo and K Hanaki ldquoImpactsof city-block-scale counter measures against urban heat islandphenomena upon a buildingrsquos energy consumption for air-conditioningrdquoApplied Energy vol 83 no 6 pp 649ndash668 2006

[28] H Taha S Konopacki and S Gabersek ldquoImpacts of large scalemodifications on meteorological conditions and energy use A10-regionmodeling studyrdquoTheoretical and Applied Climatologyvol 62 pp 175ndash185 1999

[29] Y Ashie V C Thanh and T Asaeda ldquoBuilding canopy modelfor the analysis of urban climaterdquo Journal of Wind Engineeringand Industrial Aerodynamics vol 81 pp 237ndash248 1999

[30] W T L Cow and A J Brazel ldquoAssessing xeriscaping as asustainable heat island mitigation approach for a desert cityrdquoBuilding and Environment vol 7 pp 170ndash181 2011

[31] R PriyadarsiniW N Hien and C KW David ldquoMicroclimaticmodeling oft he urban thermal environment of Singapore tomitigate urban heat islandrdquo Solar Energy vol 82 pp 727ndash7452008

[32] E Ahmadnezhad K H Naieni A Ardalan et al ldquoExcess mor-tality during heat waves Tehran Iran an ecological timeseriesstudyrdquo Journal of Research in Health Sciences vol 13 no 1 pp24ndash31 2013

[33] M Bruse and H Fleer ldquoSimulating surface-plant-air inter-actions inside urban environments with a three dimensionalnumerical modelrdquo Environmental Modelling and Software vol13 no 3-4 pp 373ndash384 1998

[34] P Zawar-Reza ldquoNumerical analysis of the 120 day wind overthe Sistan Region South-West Asia with TAPMrdquo Clean Air andEnvironmental Quality vol 41 pp 21ndash24 2008

[35] W Fisher The Cambridge History of Iran vol 1 of PhysicalGeography Cambridge University Press Cambridge UK 1968

[36] S M Habibi and B Hourcade Atlas of Tehran MetropolisPardazesh va Barnamerizi -e Shahri Publications Tehran Iran2005

[37] T R Oke Boundary Layer Climates Routledge London UK2nd edition 1987

[38] P Zawar-Reza T Appelhans M Gharaylou and A Sham-sipour ldquoMesoscale controls on particulate matter pollution fora mega city in a semi-arid mountainous environment TehranIranrdquo International Journal of Environment and Pollution vol41 no 1-2 pp 166ndash183 2010

[39] B Alijani ldquoTemporal changes of Tehran temperaturerdquo inProceedings of the Conference Proceedings of first regional onClimate Change pp 22ndash24 Tehran Iran 1997

[40] M Jahadi Toroghi ldquoVariation of temperature and precipitationof Mashhad during 1951ndash1994rdquo Iranian Quarterly GeographicalResearch Journal vol 54 pp 151ndash165 2000 (Persian)

[41] A Rasooli ldquoAnalysis of time series of Tabriz air temperaturerdquoIranian Nivar Journal vol 46 pp 7ndash26 2002 (Persian)

[42] F Rahimzadeh and A Asgari ldquoA survey on recent climatechange over IRANrdquo in Proceedings of 14th Global WarmingInternational ConferenceampExpo pp 27ndash30 BostonMass USA2003

[43] F Rahimzadeh and A Asgari ldquoA look at difference of increaserates of minimum with maximum temperature and at decreaserates of Diurnal Temperature Range (DTR) in Iranrdquo Iranian

Quarterly Geographical Research Journal vol 73 pp 153ndash1712005 (Persian)

[44] M Pedram F Rahimzadeh F Sahraian and K Noohi ldquoChangein the frost free season length and number of frost days inthe west and east Azerbaijan provincesrdquo in Proceedings of the1st International Conference on Climate Change and the MiddleEast Past Present and Future pp 20ndash23 Istanbul TechnicalUniversity 2005

[45] F Rahimzadeh A Asgari and E Fattahi ldquoVariability of extremetemperature and precipitation in Iran during recent decadesrdquoInternational Journal of Climatology vol 29 no 3 pp 329ndash3432009

[46] S Marofi M M Sohrabi K Mohammadi A A Sabziparvarand H Z Abyaneh Investigation of Meteorological ExtremeEvents over Coastal Regions of Iran Springer 2010

[47] F Tagavi and H Mohammadi ldquoStudying the return period ofclimatic extreme events in order to understand their environ-mental effectsrdquo Journal Environmental Studies vol 43 pp 11ndash202007

[48] S Alijani and B Alijani ldquoAnalysis of climate hazards in relationto urban designing in Iranrdquo Advances in Sciences and Researchvol 6 pp 173ndash178 2011

[49] M VahediTehran vamasarsquoel-e zist mohiti Seminar-e tadavom-ehayat dar baft-e shahrha-ye ghadimi-e Elm va Sanrsquoat UniversityPress Tehran Iran 1989

[50] D O Astrom F Bertil and R Joacim ldquoHeat wave impact onmorbidity and mortality in the elderly population a review ofrecent studiesrdquoMaturitas vol 69 no 2 pp 99ndash105 2011

[51] S Lofti and M J Koohsari ldquoMeasuring objective accessibilityto neighborhood facilities in the city (a case study zone 6 inTehran Iran)rdquo Cities vol 26 no 3 pp 133ndash140 2009

[52] A R Saatabadi and A A Bidokhti ldquoUrbanization effectson local climate in Tehran Megapolisrdquo Research Journal ofEnvironmental Sciences vol 5 no 1 pp 1ndash21 2011

[53] P Shahmohamadi U Cubasch S Sodoudi and A I Che-AniAir Pollution chapter 11 INTECH Press 2012 edited by BHaryanto

[54] E Ng L Chen Y Wang and C Yuan ldquoA study on the coolingeffects of greening in a high-density city an experience fromHong Kongrdquo Building and Environment vol 47 no 1 pp 256ndash271 2012

[55] C Rosenzweig W D Solecki L Parshall M ChoppingG Pope and R Goldberg ldquoCharacterizing the urban heatisland in current and future climates in New Jerseyrdquo GlobalEnvironmental Change B vol 6 no 1 pp 51ndash62 2005

[56] I D Stewart ldquoA systematic review and scientific critique ofmethodology in modern urban heat island literaturerdquo Interna-tional Journal of Climatology vol 31 no 2 pp 200ndash217 2011

[57] Y Zhou and J M Shepherd ldquoAtlantas urban heat island underextreme heat conditions and potential mitigation strategiesrdquoNatural Hazards vol 52 no 3 pp 639ndash668 2010

[58] Y H Kim and J J Baik ldquoMaximum urban heat island intensityin Seoulrdquo Journal of Applied Meteorolgy vol 41 pp 651ndash6592002

[59] J Unger Z Sumeghy and J Zoboki ldquoTemperature cross-sectionfeatures in an urban areardquo Atmospheric Research vol 58 no 2pp 117ndash127 2001

[60] Y Liu F Chen TWarner S Swerdlin J Bowers and S Halvor-son ldquoImprovements to surface flux computations in a non-local-mixing PBL scheme and refinements on urban processes


in the Noah land-surface model with the NCARATEC real-time FDDA and forecast systemrdquo in Proceedings of the 20thConference onWeather Analysis and Forecasting16th Conferenceon Numerical Weather Prediction Seattle Wash USA January2004

[61] S Sodoudi A Noorian M Geb and E Reimer ldquoDaily precip-itation forecast of ECMWF verified over Iranrdquo Theoretical andApplied Climatology vol 99 no 1-2 pp 39ndash51 2010

[62] G R Roshan S Z Shahraki D Sauri and R Borna ldquoUrbansprawl and climatic changes in Tehranrdquo Iranian Journal ofEnvironmental Health Science and Engineering vol 7 no 1 pp43ndash52 2010

[63] W T L Chow and A J Brazel ldquoAssessing xeriscaping as asustainable heat island mitigation approach for a desert cityrdquoBuilding and Environment vol 47 no 1 pp 170ndash181 2012

[64] X Yang L Zhao M Bruse and Q Meng ldquoEvaluation of amicroclimate model for predicting the thermal behavior ofdifferent ground surfacesrdquo Building and Environment vol 60pp 93ndash104 2013

[65] Y Kikegawa Y Genchi H Kondo and K Hanaki ldquoImpactsof city-block-scale countermeasures against urban heat-islandphenomena upon a buildingrsquos energy-consumption for air-conditioningrdquoApplied Energy vol 83 no 6 pp 649ndash668 2006

[66] Y Ashie V T Ca and T Asaeda ldquoBuilding canopy model forthe analysis of urban climaterdquo Journal of Wind Engineering ampIndustrial Aerodynamics vol 81 pp 237ndash248 1999

[67] H R Jahani ldquoRole of ground water in the Tehran water supplyrdquoin Groundwater Management Practices A N Findikakis and KSato Eds pp 111ndash122 CRC Press New York NY USA 2011

[68] S E Asgharpour H Zanjani and G Taleghani ldquoImpact ofurbanization on population changes in metropolitan area ofTehran Iranrdquo in Proceedings of the 3rd International GeographySymposium-GEOMED Symposium Proceedings 2013

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ClimatologyJournal of

EcologyInternational Journal of


EarthquakesJournal of


Hindawi Publishing Corporationhttpwwwhindawicom

Applied ampEnvironmentalSoil Science

Volume 2014

Mining


Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal of

Geophysics

OceanographyInternational Journal of


Journal of Computational Environmental SciencesHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofPetroleum Engineering


GeochemistryHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Atmospheric SciencesInternational Journal of


OceanographyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in


MineralogyInternational Journal of


MeteorologyAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Paleontology JournalHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014


Geological ResearchJournal of


Geology Advances in


as the lack of vegetation The main reasons of the formationof the UHI are the low albedo and the high heat capacity ofbuilt-up surfaces such as concrete or asphalt which absorbhigh amount of the short-wave radiation during the day thisenergy is then slowly released during the night as long-waveradiation and leads to higher air temperature in the urbanareas Evapotranspiration describes the transfer of latent heatfrom the earthrsquos surface to the air via evaporating waterUrban areas tend to have less evapotranspiration relative tonatural landscapes because of the lack of vegetation Thisreduced moisture in built up areas leads to dry imperviousurban infrastructure reaching very high surface tempera-tures which contribute to higher air temperatures With adecreased amount of vegetation cities also lose the shadeand cooling effect of trees Therefore greenery and usinghigh albedo materials are two strategies which can mitigatethe UHI The location of city has direct impact on theformation of UHI Different locations within a given regionvary greatly in their temperature wind conditions humidityprecipitation fog and so forth Such variationsmay be causedby differences in distance from the sea altitude direction ofslopes and the general topography of the area [11] Wind andhumidity are two main variables which control the intensityof UHI The formation of UHI phenomenon depends uponthe size and density of the population Oke [12] has correlatedUHI intensity to the size of the urban population Theyhave a direct relationship in which with higher populationUHI intensity will be increased Buildings and the densityof built-up area modify the wind the radiative balance andthe temperature conditions near the ground level as built-up area have lower albedo and higher heat capacity com-paring to natural surfaces Therefore the fraction of built-up area is a relevant factor in formation of UHI [11] Urbangeometry can impede the release of long-wave radiation intothe atmosphere When buildings absorb incoming short-wave radiation they can re-radiate that energy as long-wave energy or heat However at night due to the denseinfrastructure in some developed areas that have low sky viewfactors urban areas cannot easily release long-wave radiationto the cooler open sky and this trapped heat contributes tothe urban heat island

UHI intensity is greatest under stationary high-pressuresystems in stable air and clear-sky condition It tends todisappear if cloudiness and wind speed increases The studyof Darand and Halabian [13] shows that a dominant strongridge at the upper level (850 hPa and 500 hPa Azores highpressure) which is associated with a thermal low pressureon the surface over Pakistan and Iran is the most frequentpattern from April until September in Tehran This system isaccompanied by cloudless sky and a stable boundary layerwhich leads to a higher intensity of UHI The ridge ofAzors high pressure in the upper level results in increasedconcentration of pollution when pollutants expand to theeast and are located over north part of Iran It blockedthe convection of surface air reducing vertical mixing andthereby increasing air pollutant concentrations near theground A subsidence is usually formed under the high-pressure systemsThe interactions between the low pressurescentered at the Pakistan to the north part of Iran with Azores

high pressure result in inversion occurrence in Tehran Thispattern is the most frequent and the associated concentrationof pollution is very high More frequent heatwaves and stressare projected over most regions of the densely-populatedurban areas for the next decades [14] Thus studying theUHI effect and mitigation strategies is one of the majorpriorities for planning the urban developments in megacitieslike Tehran

Greenery is a usefulmitigation strategy to reduce theUHIby cooling the air and providing shade and milder outdoorboundary conditions as well as better thermal comfort Manyresearchers have studied the effects of greenery such asgreen roofs [15ndash18] and high albedo materials [8 19ndash24] onreducing the local temperature and UHI intensity

Table 1 summarized the results of some studies on mit-igating of UHI in different cities As it shows differentUHI mitigation strategies have been applied Reroofing withlight colors and planting shade threes indicates the highestcooling effect among the other strategies (3 K) Applyingtrees with broad canopies within residential yards led also to24 K temperature reduction although other studies indicatea cooling effect between 05ndash16 K which show the highercooling effect of shade trees in comparison to planting groundlevel vegetation or using high albedo materials

The UHI has a direct impact on human health due tohigher temperature which is responsible for the morbidityand mortality risks Both the planning and policies for urbanenvironmental sustainability in the metropolitan area ofTehran are impossible without a temperature mitigation pol-icy Mesoscale air flows such as sea breezes mountain valleywinds (slope-winds) and the urban heat-island circulationspartly control the local weather and pollutant transportworldwide

Themain aim of this paper is to study the effects of green-ery in connection with the high albedo materials in reducingthe UHI effect in themetropolitan area of Tehran and findingamitigation policy for adapting the infrastructure against themicroclimate changes However there is a lack of researchin the context of Tehran UHI In this paper we have appliedsatellite data mobile measurements and permanent stationsin order to study the UHI of Tehran

The effect of greenery and high albedo materials on localclimate in the 6th district of Tehran has been simulated byusing themicroclimatemodel ENVI-met [33] for a typical hotsummer-day in Tehran The simulations were carried out forcurrent situations as well as under three different mitigationstrategies

2 Case Study Area

Tehran (35∘421015840N 51∘251015840E) the fastest growing city in Iranwith around 8 million inhabitants and an area of 750 km2 isone of the largest cities in the world located on the southernside of the Alborz mountain range and is limited to thehighlands and mountains in the North and East and to theflat plains and desert in the South and West (Figure 1) Theaverage annual rainfall is approximately 230mm with mostprecipitation falling in autumn and winter months Due to








[26]New park nearby










Cairo









TehranStudy area

NE

SW 0 2 4 8 12 16

51∘3599840051∘3099840051∘2599840051∘2099840051∘1599840051∘1099840051∘5998400

51∘3599840051∘3099840051∘2599840051∘2099840051∘1599840051∘1099840051∘5998400

35∘55998400

35∘50998400

35∘45998400

35∘40998400

35∘35998400

35∘30998400

35∘55998400

35∘50998400

35∘45998400

35∘40998400

35∘35998400

35∘30998400

(km)










2001 (1) 4 61 452 240 181 49 182001 (2) 4 10 493 246 211 46 252001 (3) 3 116 327 157 143 18 132002 (1) 6 98 692 366 308 42 182002 (2) 7 116 524 275 204 35 182003 1 08 1704 873 721 164 752005 (1) 11 32 1377 744 504 129 1042005 (2) 5 146 658 370 238 64 382006 (1) 7 158 881 466 303 61 542006 (2) 5 39 587 319 203 48 392006 (3) 5 113 619 322 173 64 462006 (4) 5 117 885 468 293 77 602008 (1) 7 64 868 482 343 49 642008 (2) 3 56 392 208 147 24 402009 8 192 1005 558 401 73 762010 14 27 1658 939 613 109 1432011 11 89 1353 745 476 103 112

375

38

385

39

395

40

405

Aver

age m

axim

um te

mpe

ratu

re


2001

(1)

2001

(2)

2001

(3)

2002

(1)

2002

(2)

2003

2005

(1)

2005

(2)

2006

(1)

2006

(2)

2006

(3)

2006

(4)

2008

(1)

2008

(2)

2009

2010

2011










Karaj

Tehran

Mehrabad

Geophysics

(km)

45 50 55 60

26

28

30

32

34

36

38

40

Longitude

Latit

ude

1

23

3

45

6

6

7 8

9 10

0

1112

12

13

14

1516

1718

18

19

20

21

22

N



3 Methodology







1991 1993 1995 1997 1999 2001 2003 2005 2007 200968

101214161820222426

Year

(∘C)






2

3

4

5

6

7

Janu

ary

February

March

April

May

June July

August

Septem

ber

Octob

er

Novem

ber

Decem

ber

(K)

MHR-KRJGEO-KRJ


1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010

15155

16165

17175

18185

19195

20

Year


(∘C)








TehranStudy area

NE

SW 0 15 3 6 9 12

51∘3099840051∘2099840051∘10998400

51∘3099840051∘2099840051∘10998400

35∘50998400

35∘50998400

35∘40998400

35∘30998400

(km)

Surfa

ce te

mpe

ratu

re (∘

C)

High

Low






(a) (b)
















CS HAM

VEG HYBRID













CS18072009-1500 [LT]

0 50 100 150

0

50

100

150

x (m)0 50 100 150

x (m)

y(m

)

CS19072009-0300 [LT]

25 30 35 25 30 35









HAM-CS18072009-1500 [LT]

0

50

100

150

y(m

)

0

50

100

150

y(m

)

0

50

100

150

y(m

)

VEG-CS18072009-1500 [LT]

HYBRID-CS18072009-1500 [LT]

0 50 100 150

x (m)

minus4 minus2 0 2 4

HAM-CS19072009-0300 [LT]

VEG-CS19072009-0300 [LT]

HYBRID-CS19072009-0300 [LT]

0 50 100 150

x (m)

minus4 minus2 0 2 4




Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)





1

2

3


Point 1

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)






Point 2

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)


Point 3

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)










CS18072009-1500 [LT]

0

50

100

150

0 50 100 150

x (m)

y(m

)

24 26 28 30


(a)

0 50 100 150

x (m)

VEG-CS18072009-1500 [LT]



(b)














Acknowledgments


References



















































































Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in








[26]New park nearby










Cairo









TehranStudy area

NE

SW 0 2 4 8 12 16

51∘3599840051∘3099840051∘2599840051∘2099840051∘1599840051∘1099840051∘5998400

51∘3599840051∘3099840051∘2599840051∘2099840051∘1599840051∘1099840051∘5998400

35∘55998400

35∘50998400

35∘45998400

35∘40998400

35∘35998400

35∘30998400

35∘55998400

35∘50998400

35∘45998400

35∘40998400

35∘35998400

35∘30998400

(km)










2001 (1) 4 61 452 240 181 49 182001 (2) 4 10 493 246 211 46 252001 (3) 3 116 327 157 143 18 132002 (1) 6 98 692 366 308 42 182002 (2) 7 116 524 275 204 35 182003 1 08 1704 873 721 164 752005 (1) 11 32 1377 744 504 129 1042005 (2) 5 146 658 370 238 64 382006 (1) 7 158 881 466 303 61 542006 (2) 5 39 587 319 203 48 392006 (3) 5 113 619 322 173 64 462006 (4) 5 117 885 468 293 77 602008 (1) 7 64 868 482 343 49 642008 (2) 3 56 392 208 147 24 402009 8 192 1005 558 401 73 762010 14 27 1658 939 613 109 1432011 11 89 1353 745 476 103 112

375

38

385

39

395

40

405

Aver

age m

axim

um te

mpe

ratu

re


2001

(1)

2001

(2)

2001

(3)

2002

(1)

2002

(2)

2003

2005

(1)

2005

(2)

2006

(1)

2006

(2)

2006

(3)

2006

(4)

2008

(1)

2008

(2)

2009

2010

2011










Karaj

Tehran

Mehrabad

Geophysics

(km)

45 50 55 60

26

28

30

32

34

36

38

40

Longitude

Latit

ude

1

23

3

45

6

6

7 8

9 10

0

1112

12

13

14

1516

1718

18

19

20

21

22

N



3 Methodology







1991 1993 1995 1997 1999 2001 2003 2005 2007 200968

101214161820222426

Year

(∘C)






2

3

4

5

6

7

Janu

ary

February

March

April

May

June July

August

Septem

ber

Octob

er

Novem

ber

Decem

ber

(K)

MHR-KRJGEO-KRJ


1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010

15155

16165

17175

18185

19195

20

Year


(∘C)








TehranStudy area

NE

SW 0 15 3 6 9 12

51∘3099840051∘2099840051∘10998400

51∘3099840051∘2099840051∘10998400

35∘50998400

35∘50998400

35∘40998400

35∘30998400

(km)

Surfa

ce te

mpe

ratu

re (∘

C)

High

Low






(a) (b)
















CS HAM

VEG HYBRID













CS18072009-1500 [LT]

0 50 100 150

0

50

100

150

x (m)0 50 100 150

x (m)

y(m

)

CS19072009-0300 [LT]

25 30 35 25 30 35









HAM-CS18072009-1500 [LT]

0

50

100

150

y(m

)

0

50

100

150

y(m

)

0

50

100

150

y(m

)

VEG-CS18072009-1500 [LT]

HYBRID-CS18072009-1500 [LT]

0 50 100 150

x (m)

minus4 minus2 0 2 4

HAM-CS19072009-0300 [LT]

VEG-CS19072009-0300 [LT]

HYBRID-CS19072009-0300 [LT]

0 50 100 150

x (m)

minus4 minus2 0 2 4




Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)





1

2

3


Point 1

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)






Point 2

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)


Point 3

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)










CS18072009-1500 [LT]

0

50

100

150

0 50 100 150

x (m)

y(m

)

24 26 28 30


(a)

0 50 100 150

x (m)

VEG-CS18072009-1500 [LT]



(b)














Acknowledgments


References



















































































Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in


TehranStudy area

NE

SW 0 2 4 8 12 16

51∘3599840051∘3099840051∘2599840051∘2099840051∘1599840051∘1099840051∘5998400

51∘3599840051∘3099840051∘2599840051∘2099840051∘1599840051∘1099840051∘5998400

35∘55998400

35∘50998400

35∘45998400

35∘40998400

35∘35998400

35∘30998400

35∘55998400

35∘50998400

35∘45998400

35∘40998400

35∘35998400

35∘30998400

(km)










2001 (1) 4 61 452 240 181 49 182001 (2) 4 10 493 246 211 46 252001 (3) 3 116 327 157 143 18 132002 (1) 6 98 692 366 308 42 182002 (2) 7 116 524 275 204 35 182003 1 08 1704 873 721 164 752005 (1) 11 32 1377 744 504 129 1042005 (2) 5 146 658 370 238 64 382006 (1) 7 158 881 466 303 61 542006 (2) 5 39 587 319 203 48 392006 (3) 5 113 619 322 173 64 462006 (4) 5 117 885 468 293 77 602008 (1) 7 64 868 482 343 49 642008 (2) 3 56 392 208 147 24 402009 8 192 1005 558 401 73 762010 14 27 1658 939 613 109 1432011 11 89 1353 745 476 103 112

375

38

385

39

395

40

405

Aver

age m

axim

um te

mpe

ratu

re


2001

(1)

2001

(2)

2001

(3)

2002

(1)

2002

(2)

2003

2005

(1)

2005

(2)

2006

(1)

2006

(2)

2006

(3)

2006

(4)

2008

(1)

2008

(2)

2009

2010

2011










Karaj

Tehran

Mehrabad

Geophysics

(km)

45 50 55 60

26

28

30

32

34

36

38

40

Longitude

Latit

ude

1

23

3

45

6

6

7 8

9 10

0

1112

12

13

14

1516

1718

18

19

20

21

22

N



3 Methodology







1991 1993 1995 1997 1999 2001 2003 2005 2007 200968

101214161820222426

Year

(∘C)






2

3

4

5

6

7

Janu

ary

February

March

April

May

June July

August

Septem

ber

Octob

er

Novem

ber

Decem

ber

(K)

MHR-KRJGEO-KRJ


1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010

15155

16165

17175

18185

19195

20

Year


(∘C)








TehranStudy area

NE

SW 0 15 3 6 9 12

51∘3099840051∘2099840051∘10998400

51∘3099840051∘2099840051∘10998400

35∘50998400

35∘50998400

35∘40998400

35∘30998400

(km)

Surfa

ce te

mpe

ratu

re (∘

C)

High

Low






(a) (b)
















CS HAM

VEG HYBRID













CS18072009-1500 [LT]

0 50 100 150

0

50

100

150

x (m)0 50 100 150

x (m)

y(m

)

CS19072009-0300 [LT]

25 30 35 25 30 35









HAM-CS18072009-1500 [LT]

0

50

100

150

y(m

)

0

50

100

150

y(m

)

0

50

100

150

y(m

)

VEG-CS18072009-1500 [LT]

HYBRID-CS18072009-1500 [LT]

0 50 100 150

x (m)

minus4 minus2 0 2 4

HAM-CS19072009-0300 [LT]

VEG-CS19072009-0300 [LT]

HYBRID-CS19072009-0300 [LT]

0 50 100 150

x (m)

minus4 minus2 0 2 4




Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)





1

2

3


Point 1

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)






Point 2

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)


Point 3

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)










CS18072009-1500 [LT]

0

50

100

150

0 50 100 150

x (m)

y(m

)

24 26 28 30


(a)

0 50 100 150

x (m)

VEG-CS18072009-1500 [LT]



(b)














Acknowledgments


References



















































































Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in




2001 (1) 4 61 452 240 181 49 182001 (2) 4 10 493 246 211 46 252001 (3) 3 116 327 157 143 18 132002 (1) 6 98 692 366 308 42 182002 (2) 7 116 524 275 204 35 182003 1 08 1704 873 721 164 752005 (1) 11 32 1377 744 504 129 1042005 (2) 5 146 658 370 238 64 382006 (1) 7 158 881 466 303 61 542006 (2) 5 39 587 319 203 48 392006 (3) 5 113 619 322 173 64 462006 (4) 5 117 885 468 293 77 602008 (1) 7 64 868 482 343 49 642008 (2) 3 56 392 208 147 24 402009 8 192 1005 558 401 73 762010 14 27 1658 939 613 109 1432011 11 89 1353 745 476 103 112

375

38

385

39

395

40

405

Aver

age m

axim

um te

mpe

ratu

re


2001

(1)

2001

(2)

2001

(3)

2002

(1)

2002

(2)

2003

2005

(1)

2005

(2)

2006

(1)

2006

(2)

2006

(3)

2006

(4)

2008

(1)

2008

(2)

2009

2010

2011










Karaj

Tehran

Mehrabad

Geophysics

(km)

45 50 55 60

26

28

30

32

34

36

38

40

Longitude

Latit

ude

1

23

3

45

6

6

7 8

9 10

0

1112

12

13

14

1516

1718

18

19

20

21

22

N



3 Methodology







1991 1993 1995 1997 1999 2001 2003 2005 2007 200968

101214161820222426

Year

(∘C)






2

3

4

5

6

7

Janu

ary

February

March

April

May

June July

August

Septem

ber

Octob

er

Novem

ber

Decem

ber

(K)

MHR-KRJGEO-KRJ


1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010

15155

16165

17175

18185

19195

20

Year


(∘C)








TehranStudy area

NE

SW 0 15 3 6 9 12

51∘3099840051∘2099840051∘10998400

51∘3099840051∘2099840051∘10998400

35∘50998400

35∘50998400

35∘40998400

35∘30998400

(km)

Surfa

ce te

mpe

ratu

re (∘

C)

High

Low






(a) (b)
















CS HAM

VEG HYBRID













CS18072009-1500 [LT]

0 50 100 150

0

50

100

150

x (m)0 50 100 150

x (m)

y(m

)

CS19072009-0300 [LT]

25 30 35 25 30 35









HAM-CS18072009-1500 [LT]

0

50

100

150

y(m

)

0

50

100

150

y(m

)

0

50

100

150

y(m

)

VEG-CS18072009-1500 [LT]

HYBRID-CS18072009-1500 [LT]

0 50 100 150

x (m)

minus4 minus2 0 2 4

HAM-CS19072009-0300 [LT]

VEG-CS19072009-0300 [LT]

HYBRID-CS19072009-0300 [LT]

0 50 100 150

x (m)

minus4 minus2 0 2 4




Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)





1

2

3


Point 1

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)






Point 2

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)


Point 3

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)










CS18072009-1500 [LT]

0

50

100

150

0 50 100 150

x (m)

y(m

)

24 26 28 30


(a)

0 50 100 150

x (m)

VEG-CS18072009-1500 [LT]



(b)














Acknowledgments


References



















































































Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in


Karaj

Tehran

Mehrabad

Geophysics

(km)

45 50 55 60

26

28

30

32

34

36

38

40

Longitude

Latit

ude

1

23

3

45

6

6

7 8

9 10

0

1112

12

13

14

1516

1718

18

19

20

21

22

N



3 Methodology







1991 1993 1995 1997 1999 2001 2003 2005 2007 200968

101214161820222426

Year

(∘C)






2

3

4

5

6

7

Janu

ary

February

March

April

May

June July

August

Septem

ber

Octob

er

Novem

ber

Decem

ber

(K)

MHR-KRJGEO-KRJ


1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010

15155

16165

17175

18185

19195

20

Year


(∘C)








TehranStudy area

NE

SW 0 15 3 6 9 12

51∘3099840051∘2099840051∘10998400

51∘3099840051∘2099840051∘10998400

35∘50998400

35∘50998400

35∘40998400

35∘30998400

(km)

Surfa

ce te

mpe

ratu

re (∘

C)

High

Low






(a) (b)
















CS HAM

VEG HYBRID













CS18072009-1500 [LT]

0 50 100 150

0

50

100

150

x (m)0 50 100 150

x (m)

y(m

)

CS19072009-0300 [LT]

25 30 35 25 30 35









HAM-CS18072009-1500 [LT]

0

50

100

150

y(m

)

0

50

100

150

y(m

)

0

50

100

150

y(m

)

VEG-CS18072009-1500 [LT]

HYBRID-CS18072009-1500 [LT]

0 50 100 150

x (m)

minus4 minus2 0 2 4

HAM-CS19072009-0300 [LT]

VEG-CS19072009-0300 [LT]

HYBRID-CS19072009-0300 [LT]

0 50 100 150

x (m)

minus4 minus2 0 2 4




Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)





1

2

3


Point 1

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)






Point 2

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)


Point 3

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)










CS18072009-1500 [LT]

0

50

100

150

0 50 100 150

x (m)

y(m

)

24 26 28 30


(a)

0 50 100 150

x (m)

VEG-CS18072009-1500 [LT]



(b)














Acknowledgments


References



















































































Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in


1991 1993 1995 1997 1999 2001 2003 2005 2007 200968

101214161820222426

Year

(∘C)






2

3

4

5

6

7

Janu

ary

February

March

April

May

June July

August

Septem

ber

Octob

er

Novem

ber

Decem

ber

(K)

MHR-KRJGEO-KRJ


1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010

15155

16165

17175

18185

19195

20

Year


(∘C)








TehranStudy area

NE

SW 0 15 3 6 9 12

51∘3099840051∘2099840051∘10998400

51∘3099840051∘2099840051∘10998400

35∘50998400

35∘50998400

35∘40998400

35∘30998400

(km)

Surfa

ce te

mpe

ratu

re (∘

C)

High

Low






(a) (b)
















CS HAM

VEG HYBRID













CS18072009-1500 [LT]

0 50 100 150

0

50

100

150

x (m)0 50 100 150

x (m)

y(m

)

CS19072009-0300 [LT]

25 30 35 25 30 35









HAM-CS18072009-1500 [LT]

0

50

100

150

y(m

)

0

50

100

150

y(m

)

0

50

100

150

y(m

)

VEG-CS18072009-1500 [LT]

HYBRID-CS18072009-1500 [LT]

0 50 100 150

x (m)

minus4 minus2 0 2 4

HAM-CS19072009-0300 [LT]

VEG-CS19072009-0300 [LT]

HYBRID-CS19072009-0300 [LT]

0 50 100 150

x (m)

minus4 minus2 0 2 4




Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)





1

2

3


Point 1

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)






Point 2

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)


Point 3

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)










CS18072009-1500 [LT]

0

50

100

150

0 50 100 150

x (m)

y(m

)

24 26 28 30


(a)

0 50 100 150

x (m)

VEG-CS18072009-1500 [LT]



(b)














Acknowledgments


References



















































































Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in






TehranStudy area

NE

SW 0 15 3 6 9 12

51∘3099840051∘2099840051∘10998400

51∘3099840051∘2099840051∘10998400

35∘50998400

35∘50998400

35∘40998400

35∘30998400

(km)

Surfa

ce te

mpe

ratu

re (∘

C)

High

Low






(a) (b)
















CS HAM

VEG HYBRID













CS18072009-1500 [LT]

0 50 100 150

0

50

100

150

x (m)0 50 100 150

x (m)

y(m

)

CS19072009-0300 [LT]

25 30 35 25 30 35









HAM-CS18072009-1500 [LT]

0

50

100

150

y(m

)

0

50

100

150

y(m

)

0

50

100

150

y(m

)

VEG-CS18072009-1500 [LT]

HYBRID-CS18072009-1500 [LT]

0 50 100 150

x (m)

minus4 minus2 0 2 4

HAM-CS19072009-0300 [LT]

VEG-CS19072009-0300 [LT]

HYBRID-CS19072009-0300 [LT]

0 50 100 150

x (m)

minus4 minus2 0 2 4




Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)





1

2

3


Point 1

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)






Point 2

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)


Point 3

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)










CS18072009-1500 [LT]

0

50

100

150

0 50 100 150

x (m)

y(m

)

24 26 28 30


(a)

0 50 100 150

x (m)

VEG-CS18072009-1500 [LT]



(b)














Acknowledgments


References



















































































Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in


(a) (b)
















CS HAM

VEG HYBRID













CS18072009-1500 [LT]

0 50 100 150

0

50

100

150

x (m)0 50 100 150

x (m)

y(m

)

CS19072009-0300 [LT]

25 30 35 25 30 35









HAM-CS18072009-1500 [LT]

0

50

100

150

y(m

)

0

50

100

150

y(m

)

0

50

100

150

y(m

)

VEG-CS18072009-1500 [LT]

HYBRID-CS18072009-1500 [LT]

0 50 100 150

x (m)

minus4 minus2 0 2 4

HAM-CS19072009-0300 [LT]

VEG-CS19072009-0300 [LT]

HYBRID-CS19072009-0300 [LT]

0 50 100 150

x (m)

minus4 minus2 0 2 4




Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)





1

2

3


Point 1

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)






Point 2

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)


Point 3

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)










CS18072009-1500 [LT]

0

50

100

150

0 50 100 150

x (m)

y(m

)

24 26 28 30


(a)

0 50 100 150

x (m)

VEG-CS18072009-1500 [LT]



(b)














Acknowledgments


References



















































































Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in










CS HAM

VEG HYBRID













CS18072009-1500 [LT]

0 50 100 150

0

50

100

150

x (m)0 50 100 150

x (m)

y(m

)

CS19072009-0300 [LT]

25 30 35 25 30 35









HAM-CS18072009-1500 [LT]

0

50

100

150

y(m

)

0

50

100

150

y(m

)

0

50

100

150

y(m

)

VEG-CS18072009-1500 [LT]

HYBRID-CS18072009-1500 [LT]

0 50 100 150

x (m)

minus4 minus2 0 2 4

HAM-CS19072009-0300 [LT]

VEG-CS19072009-0300 [LT]

HYBRID-CS19072009-0300 [LT]

0 50 100 150

x (m)

minus4 minus2 0 2 4




Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)





1

2

3


Point 1

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)






Point 2

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)


Point 3

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)










CS18072009-1500 [LT]

0

50

100

150

0 50 100 150

x (m)

y(m

)

24 26 28 30


(a)

0 50 100 150

x (m)

VEG-CS18072009-1500 [LT]



(b)














Acknowledgments


References



















































































Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in


CS HAM

VEG HYBRID













CS18072009-1500 [LT]

0 50 100 150

0

50

100

150

x (m)0 50 100 150

x (m)

y(m

)

CS19072009-0300 [LT]

25 30 35 25 30 35









HAM-CS18072009-1500 [LT]

0

50

100

150

y(m

)

0

50

100

150

y(m

)

0

50

100

150

y(m

)

VEG-CS18072009-1500 [LT]

HYBRID-CS18072009-1500 [LT]

0 50 100 150

x (m)

minus4 minus2 0 2 4

HAM-CS19072009-0300 [LT]

VEG-CS19072009-0300 [LT]

HYBRID-CS19072009-0300 [LT]

0 50 100 150

x (m)

minus4 minus2 0 2 4




Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)





1

2

3


Point 1

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)






Point 2

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)


Point 3

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)










CS18072009-1500 [LT]

0

50

100

150

0 50 100 150

x (m)

y(m

)

24 26 28 30


(a)

0 50 100 150

x (m)

VEG-CS18072009-1500 [LT]



(b)














Acknowledgments


References



















































































Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in


CS18072009-1500 [LT]

0 50 100 150

0

50

100

150

x (m)0 50 100 150

x (m)

y(m

)

CS19072009-0300 [LT]

25 30 35 25 30 35









HAM-CS18072009-1500 [LT]

0

50

100

150

y(m

)

0

50

100

150

y(m

)

0

50

100

150

y(m

)

VEG-CS18072009-1500 [LT]

HYBRID-CS18072009-1500 [LT]

0 50 100 150

x (m)

minus4 minus2 0 2 4

HAM-CS19072009-0300 [LT]

VEG-CS19072009-0300 [LT]

HYBRID-CS19072009-0300 [LT]

0 50 100 150

x (m)

minus4 minus2 0 2 4




Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)





1

2

3


Point 1

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)






Point 2

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)


Point 3

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)










CS18072009-1500 [LT]

0

50

100

150

0 50 100 150

x (m)

y(m

)

24 26 28 30


(a)

0 50 100 150

x (m)

VEG-CS18072009-1500 [LT]



(b)














Acknowledgments


References



















































































Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in


HAM-CS18072009-1500 [LT]

0

50

100

150

y(m

)

0

50

100

150

y(m

)

0

50

100

150

y(m

)

VEG-CS18072009-1500 [LT]

HYBRID-CS18072009-1500 [LT]

0 50 100 150

x (m)

minus4 minus2 0 2 4

HAM-CS19072009-0300 [LT]

VEG-CS19072009-0300 [LT]

HYBRID-CS19072009-0300 [LT]

0 50 100 150

x (m)

minus4 minus2 0 2 4




Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)





1

2

3


Point 1

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)






Point 2

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)


Point 3

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)










CS18072009-1500 [LT]

0

50

100

150

0 50 100 150

x (m)

y(m

)

24 26 28 30


(a)

0 50 100 150

x (m)

VEG-CS18072009-1500 [LT]



(b)














Acknowledgments


References



















































































Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in


Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)





1

2

3


Point 1

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)






Point 2

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)


Point 3

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)










CS18072009-1500 [LT]

0

50

100

150

0 50 100 150

x (m)

y(m

)

24 26 28 30


(a)

0 50 100 150

x (m)

VEG-CS18072009-1500 [LT]



(b)














Acknowledgments


References



















































































Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in


Point 2

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)


Point 3

Local time (h)9 12 15 18 21 0 3

20

24

28

32

36

CSHAM

VEGHYBRID

2m

pot

entia

l tem

pera

ture

(∘C)










CS18072009-1500 [LT]

0

50

100

150

0 50 100 150

x (m)

y(m

)

24 26 28 30


(a)

0 50 100 150

x (m)

VEG-CS18072009-1500 [LT]



(b)














Acknowledgments


References



















































































Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in


CS18072009-1500 [LT]

0

50

100

150

0 50 100 150

x (m)

y(m

)

24 26 28 30


(a)

0 50 100 150

x (m)

VEG-CS18072009-1500 [LT]



(b)














Acknowledgments


References



















































































Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in







Acknowledgments


References



















































































Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in


























































Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in




















Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in










Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in

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