METEOROLOGICAL TARGETS

TO DETECT STORMS AND OTHER WEATHER PHENOMENA

SEVERE STORM AND TORNADO WARNINGS, HURRICANE OBSERVATIONS, FLOOD WARNINGS AND WINDSHEAR WARNINGS SAVING OF LIVES AND POPERTY

CLOUDSCLOUDS

not precipitating cloud: Small particles, new cloud

Clouds Water droplets + ice crystals or both, Temp. and others

Liquid droplets 0 °C Supercooled : 0 °C - (-40) °C

Size distribution

Kind

age

height

Geographic location

The farther from cloud base The larger the droplets are

As a cloud gets older Droplets get larger

Maritime clouds Continental clouds

Droplets sizes : 5 – 100 m

The mean droplet size distributions for various cloud types.

(Fletcher, 1966)

Cu

St

As

z : generally quite weak 6ii DNz

Diameter (m)

Number ND6 (mm6/m3)

5 100 1.56.10-6

10 100 1.00.10-4

15 50 5.69.10-6

20 25 1.60.10-3

25 10 2.44.10-3

30 5 9.19.10-3

35 1 4.01.10-3

Total: 1Total: 1.80.10.80.10-2-2=-17.4 dBz=-17.4 dBz

RAINRAINEasly detectable Raindrop size dist. 30-40 years

One technique Raindrop camera

From these distributions

Rainrate (mm/h)

Liquid water content (g/m3)

Radar reflectivity (mm6/m3)

Marshall and Palmer drop-size distributions compared with the results of Laws and Parsons.

The Marshall-Palmer relationsihip is given by

Dod eNN .

ND : approximate size distribution (number of drops)

No : 8000/m3mm

D : droplet diameter (mm)

: wavelength

21.01.4 R R : rainrate in mm/h

Using these,,,,, obtain : the number of drops per unit volume

Z-R RELEATIONSHIP

By plotting

rainrate

reflectivity

Correlate statisticallay Z-R rel.

Emprical relationship: bRAz .R : rainrate in mm/hZ : rad. ref. Factor (mm6/m3)A, b : emprical constants

Battan (1973) : 60 experiments for Z-R

Most commonly used Z-R : 6.1.200 Rz

(Marshall and Palmer)

Z for rain :Z for rain :From 20 dBZ (100 mmFrom 20 dBZ (100 mm66/m/m33) ) to 50 dBZ (100 000 mmto 50 dBZ (100 000 mm66/m/m33) )

Z for storms :Z for storms : 75 dBZ75 dBZ

Z for hail :Z for hail : 55 dBZ55 dBZ

NWS’s results for rainrate and reflectivitiy :NWS’s results for rainrate and reflectivitiy :

Rainrate (in/h)Rainrate (in/h) Reflectivity (dBZ)Reflectivity (dBZ)0.1 29.5

0.25 39.5

0.5 40.7

1.25 47.0

2.5 51.9

4.0 55.1

SNOWSNOW Easily detectable

Snow and Rain differences

1.1. Precipitation rate for snow is usually mucc less than it is for rain. “water equivalent” precipitation rate

MOISTURE --- TEMPERATURE :

at warm temp. more water vapor at cold temp.

heaviest snows : above the melting temp. of ice, 33 ° to 36 °F

2.2. DECice DECwater DEC : the dielectric constant

2K term in the radar equation :

0.93 for water

0.197 for ice

The primary reason snow is not detectable by radar is the shallow height of typical snow storms.

Snow storms are usually much lower than most rain storms.

Snow storms are often very widespread in area, but they may only extend a few thousand meters above the surface.

SNOW IS LESS EASILY DETECTABLE THAN RAIN..

HAIL

HAIL : A precipitation in the form of ice.

Diameter : 5 mm (at least)

thunderstorms Lightning and thunder

85 % of thunderstorms contain hail (at least during part of their lives)

Diameter : ranges from 5 mm to 10 cm

World’s record hailstoneCoeffeville, Kansas,14 September 197214 cm (longest dimension)

Terminal Velocity of Hail

Hailstone diameter Shape of the hail Density of the air

Measurements and calculations for Vt :5.0.DAVt

D : hailstone diameter (usually in cm)

Vt : terminal velocity (in m/s)

A : an emprical constant. Measurements for A ; 11.45 (Matson and Huggins, 1979)

Z from hail depends upon wether the outside surface is WET or DRY.

Dry hail has a lower reflectivity than wet hail of the same size.

HAILSTONES MIE REGION

For =3 cm and 5 cm radars MIE REGION

For =10 cm radars RAYLEIGH REGION

DISCUSSIONS

Besides those already discussed ; there are certainly other targets of meteorological interest. Among those are: TORNADOES, HURRICANES, MCC’s and various WIND PHENOMENA

Tornadoes : prevalent within USA, to detect ---- WSR-88D radars

NEXRAD algorithms are being used specifically for the detection of mesocyclones and tornedoes themselves.

Hurricanes generally form hundreds or thousands of kilometers away from land. Ground-based radars have detectable ranges on the order of 400 km or so. Consequently, hurricanes are not detected until they have moved close enough to land to already be a problem. But Doppler radars have been used in stduying H.

MCC’s are complexes of numerous storms. As such, the various components are just as detectable as they would be if they occured individually.

MCC’s are sometimes so large, however, that a single radardoes not have the ability to cover the entire event; they are justtoo extensive.

DATA from more than one radar are rouitnely combined, fortunately, so that entire events can be monitored by ground-based radar networks.

The NEXRAD network will add velocity measurements to the reflectivity measurements already available and should provide even more useful information to study this events.

Both technological comfort and scientific researches can be presented for people using by radars in developed countries especially.

Some natural disasters (meteorologically) such as avalanche, flood, tornado have occured in many regions of the world and they have caused to the death of huming beings and bringing greate ecenomic losses.

Therefore, radars have a great importance in determining of the natural disasters and its early warning systems.

National Weather Service Doppler Radars

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Turkish State Meteorological Service Radars

SELECTED TOPICS FOR NEXT SELECTED TOPICS FOR NEXT SEMINAR ARE:SEMINAR ARE:

Clear-Air Return

Doppler, NEXRAD and TDWR radars

Advanced uses of Meteorological Radars

Radar Maps and Interpretations

R E F E R E N C E S (selected)R E F E R E N C E S (selected) Atlas, D., 1990: Radar in Meteorology, Boston, Amer. Meteor. Soc., 806 pp. Battan, L. J., 1973: Radar Observation of the Atmosphere, Chicago, University of Chicago

Press, 324 pp., [Reprinted by: TechBooks, 2600 Seskey Glen Court, Herndon, VA 22071].

Buderi, R., 1996: The Invention That Changed the World, Simon & Schuster, New York, 575 pp.

 Doviak, R. J. and D. S. Zrnic, , 1993: Doppler Radar and Weather Observations, Second

Edition, San Diego, AcademicPress, Inc., 562 pp. Marshall, J. S. and W. McK. Palmer, 1948: The Distribution of Raindrops with Size, J.

Meteor., 5, 165-166. Matson, R. and A. W. Huggins, 1979: Field Observations of the Kinematics of Hailstorms,

NCAR/CSD, Boulder, NCAR /TN-139+STR, 68 pp. Rinehart, R. E., 2001: Radar for Meteorologists, Rinehart Publicatipns, Columbia, MO, 427

pp. 

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