Climate & Introduction to Earth System Science Meteorology & … · 2007-09-12 · 2 Introduction to Meteorology & Climate Weather Satellite Image, July 7, 2005 Introduction to Meteorology

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Introduction to Meteorology & Climate

Climate & Earth System Science

Peter LynchMeteorology & Climate Centre

School of Mathematical SciencesUniversity College Dublin


Introduction toMeteorology & Climate

MAPH 10050

Peter Lynch

Meteorology & Climate CentreSchool of Mathematical SciencesUniversity College Dublin


Introduction to the AtmosphereIntroduction to the Atmosphere

CHAPTER 1CHAPTER 1


OUR HOME


Question:Question:

What if there were no atmosphere What if there were no atmosphere on Earth?on Earth?

No lakes or oceansNo soundsNo cloudsCold nights, hot daysNo weatherNo life!


The Constituents of the AtmosphereThe Constituents of the Atmosphere

LECTURE 1LECTURE 1

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Weather Satellite Image, July 7, 2005


WEATHERWEATHERWeather is the condition of the atmosphere Weather is the condition of the atmosphere at a particular location and moment.at a particular location and moment.

The condition of the atmosphere is The condition of the atmosphere is expressed according to the following:expressed according to the following:

TemperatureTemperatureHumidity (relative humidity, dew point)Humidity (relative humidity, dew point)PressurePressureWind Speed and DirectionWind Speed and DirectionCloud CoverCloud CoverPrecipitation (type and amount)Precipitation (type and amount)


CLIMATECLIMATEClimate is the condition of the Climate is the condition of the atmosphere over many years.atmosphere over many years.The same atmospheric variables are The same atmospheric variables are used for climate as weather.used for climate as weather.Climate data include the following:Climate data include the following:

AveragesAverages (“normal high” = 30 year (“normal high” = 30 year average high temperatures for a given average high temperatures for a given date and location)date and location)ExtremesExtremes (“record high” = highest (“record high” = highest temperature ever recorded for a given temperature ever recorded for a given date and location)date and location)


WEATHER WEATHER vv. CLIMATE. CLIMATE

WeatherWeather

Instantaneous Instantaneous description of what description of what the atmosphere is the atmosphere is doing doing at a particular at a particular time and place.time and place.

ClimateClimate

Description of what Description of what weather is usually weather is usually like in a region .like in a region .

Not just the Not just the averageaverageweather, but a weather, but a description of what description of what the the extremesextremes are like are like too. too.


Typical Weather Map


Mean Percentage of possible sunshine for November

Typical Climatology Map

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COMPARISON OF HEMISPHERESCOMPARISON OF HEMISPHERES

Fig. 1-2, p. 3

70% of the globe covered by water70% of the globe covered by water


Atmospheric CompositionAtmospheric Composition


Table 1-1, p. 4


N2O2

Ar

O3

Inert gasesCO2

H2

←SO2, NO2,CFC’s, etc

PMCOCH4

N2O

COMPOSITION OF THE EARTH’S ATMOSPHERE

100%100%

1%1%

0.04%0.04%

0.0002%0.0002%


Table 1-1, p. 4

~78%~21%

~1%

.04%


ATMOSPHERIC COMPOSITIONATMOSPHERIC COMPOSITION

Molecular Molecular oxygenoxygen and and nitrogennitrogen are major are major components components –– 99%99%Of the remaining 1% , 96% is the inert Of the remaining 1% , 96% is the inert gas argongas argonOf the remaining 4%, 93% is carbon Of the remaining 4%, 93% is carbon dioxidedioxideAll remaining gases All remaining gases –– about 2 parts in about 2 parts in 100,000 are known as 100,000 are known as trace speciestrace speciesThese gases control the chemistry of the These gases control the chemistry of the troposphere troposphere

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Introduction to Meteorology & Climate Introduction to Meteorology & Climate

THE EARLY ATMOSPHERE

4.6 billion years ago:Earth’s gravity too weak to hold hydrogen Earth’s gravity too weak to hold hydrogen and helium (unlike Sun, Jupiter, Saturn, and helium (unlike Sun, Jupiter, Saturn, Uranus)Uranus)

Earth’s present atmosphere from Earth’s present atmosphere from volcanoes (volcanoes (outgassingoutgassing))

Water vapor condensed to form oceansWater vapor condensed to form oceansCOCO22 went into oceans and rockswent into oceans and rocksNN22

Oxygen forms by breakOxygen forms by break--up of water by up of water by sunlight, later from plants … sunlight, later from plants … photosynthesis.photosynthesis.


ATMOSPHERIC EVOLUTIONATMOSPHERIC EVOLUTION

Earth’s Earth’s early atmosphereearly atmosphere consisted of consisted of Hydrogen (H), Helium (He), Methane Hydrogen (H), Helium (He), Methane (CH(CH44) and Ammonia (NH) and Ammonia (NH33))

As the earth cooled As the earth cooled volcanic eruptionsvolcanic eruptionsoccurred emitting water occurred emitting water vapourvapour (H(H22O), O), carbon dioxide (COcarbon dioxide (CO22) and nitrogen (N) and nitrogen (N22).).

The molecular oxygen (OThe molecular oxygen (O22) in the ) in the current atmosphere came about as current atmosphere came about as single celled algaesingle celled algae developed in the developed in the oceans about 3 billion years ago. oceans about 3 billion years ago.


Oxygen is produced as a byOxygen is produced as a by--product of product of photosynthesisphotosynthesis, the making of sugars from , the making of sugars from water vapor and carbon dioxide.water vapor and carbon dioxide.

This oxygen produces This oxygen produces ozoneozone (O(O33) in the ) in the upper atmosphere which filtered out upper atmosphere which filtered out harmful ultraviolet radiation from the sun. harmful ultraviolet radiation from the sun.

This allowed This allowed plants plants andand animalsanimals to to develop on land.develop on land.

ATMOSPHERIC EVOLUTIONATMOSPHERIC EVOLUTION


Fig. 1-3, p. 6

Introduction to Meteorology & ClimateFig. 1-4, p. 7

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CARBON DIOXIDE CYCLECARBON DIOXIDE CYCLESourcesSources

Plant/animal respirationPlant/animal respirationPlant decayPlant decayVolcanoesVolcanoesBurning of fossil fuelsBurning of fossil fuelsDeforestationDeforestation

SinksSinksPlant photosynthesisPlant photosynthesisOceansOceansCarbonatesCarbonates


Fig. 1-5, p. 8

HYDROLOGICAL CYCLEHYDROLOGICAL CYCLE


HYDROLOGICAL CYCLECYCLEWater is everywhere on earthWater is everywhere on earthIt is in the oceans, glaciers, rivers, lakes, the It is in the oceans, glaciers, rivers, lakes, the atmosphere, soil, and in living tissueatmosphere, soil, and in living tissueAll these ‘reservoirs’ constitute the All these ‘reservoirs’ constitute the hydrospherehydrosphere

The continuous exchange of water between the The continuous exchange of water between the ‘reservoirs’ is called the ‘reservoirs’ is called the hydrological cyclehydrological cycleThe hydrological cycle is powered by the SunThe hydrological cycle is powered by the SunIt comprisesIt comprises

Evaporation and transpirationEvaporation and transpirationPrecipitationPrecipitationPercolation into groundPercolation into groundRunRun--off to the seaoff to the sea


Trace Constituents


Fig. 1-7, p. 9

Methane and world populationIntroduction to Meteorology & Climate

Fig. 1-8, p. 10CFCs: global production

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Fig. 1-9, p. 11CFCs: global concentrationIntroduction to Meteorology & Climate

Fig. 1-10, p. 11

Aerosols: particle sizes

1 nm 1 mm1 um|


AEROSOLSParticles suspended in the atmosphereParticles suspended in the atmosphereDiameters of microns Diameters of microns –– one millionth of a meter.one millionth of a meter.

Modify the amount of solar energy reachingModify the amount of solar energy reachingthe surface.the surface.

Act as Act as condensation nucleicondensation nuclei for cloud droplets.for cloud droplets.

PRIMARY SOURCES:PRIMARY SOURCES:Sea salt spraySea salt sprayWind erosionWind erosionVolcanoesVolcanoesFiresFiresHuman activity Human activity


Fig. 1-11, p. 12

Introduction to Meteorology & Climate Fig. 1.11Los Alamos Fire, 2000


Study Ackerman and KnoxStudy Ackerman and Knox

Chapter 1Chapter 1Pages 1Pages 1--1212

Preview remainder of chapter.Preview remainder of chapter.

Reading ExerciseReading Exercise

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Atmospheric Pressure and DensityAtmospheric Pressure and Density

LECTURE 2LECTURE 2


PRESSURE AND DENSITYPRESSURE AND DENSITY

PressurePressure is the force exerted on a given area.is the force exerted on a given area.Air pressure results when air molecules Air pressure results when air molecules move and collide with objects.move and collide with objects.Air pressure is exerted in all directions.Air pressure is exerted in all directions.

DensityDensity is the concentration of molecules, or is the concentration of molecules, or mass per unit volume.mass per unit volume.The pressure, density, and temperature of a The pressure, density, and temperature of a gas are all related to each other.gas are all related to each other.


Fig. 1-13, p. 15


PRESSURE AND ALTITUDEPRESSURE AND ALTITUDEPressure is measured in terms of inches of Pressure is measured in terms of inches of mercury, or in mercury, or in millibarsmillibars or or hectopascalshectopascals..Average seaAverage sea--level pressure is 29.92 inches level pressure is 29.92 inches of mercury or 1013.25 of mercury or 1013.25 millibarsmillibars ((hPahPa).).Atmospheric pressure always decreases Atmospheric pressure always decreases with increasing altitude.with increasing altitude.The air pressure measured on top of the The air pressure measured on top of the Sugar Loaf is always less than the pressure Sugar Loaf is always less than the pressure in in KilmacanogueKilmacanogue..To subtract the effect of station elevation, To subtract the effect of station elevation, air pressure is corrected to report what it air pressure is corrected to report what it would be at sea level (would be at sea level (sea level pressuresea level pressure))


Fig. 1.12Density decreases exponentially with heightDensity decreases exponentially with height

Introduction to Meteorology & ClimateFig. 1.13

BlaiseBlaisePascalPascal

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ATMOSPHERIC PRESSUREATMOSPHERIC PRESSURE

Pressure at a point is Pressure at a point is the weight of air above the weight of air above that point.that point.A column of air of crossA column of air of cross--section 1 square section 1 square metremetre weighs about 10 weighs about 10 tonnestonnes !!In still air, two factors determine the pressure In still air, two factors determine the pressure –– temperature and densitytemperature and densityIdeal gas law:Ideal gas law:Pressure = Constant Pressure = Constant XX Density Density XX TemperatureTemperaturePressure decreases with altitude.Pressure decreases with altitude.


ATMOSPHERIC DENSITYATMOSPHERIC DENSITY

The concentration of molecules in measured The concentration of molecules in measured in terms of in terms of densitydensity, or mass per unit volume., or mass per unit volume.

Density at sea level for temperature of 15Density at sea level for temperature of 15ºC ºC is about 1.2 kilograms per cubic is about 1.2 kilograms per cubic metremetre..

Density decreases with altitude.Density decreases with altitude.


IDEAL GAS LAWIDEAL GAS LAWThe relationship between pressure, The relationship between pressure, temperature, and volume is given by the temperature, and volume is given by the ideal gas law:ideal gas law:

p = R p = R ρρ TT

where p = pressurewhere p = pressureR = the gas constantR = the gas constantρρ = (Greek letter = (Greek letter rhorho) density) densityT = temperatureT = temperature


IDEAL GAS LAWIDEAL GAS LAW

You need to know the Ideal Gas Law.You need to know the Ideal Gas Law.

Knowing the Ideal Gas Law, you should be Knowing the Ideal Gas Law, you should be able to say what happens to one variable able to say what happens to one variable if a change in one of the others occurs if a change in one of the others occurs (while the third remains constant).(while the third remains constant).

E.g., what happens to pressure if density E.g., what happens to pressure if density increases (temperature constant)?increases (temperature constant)?


STRATIFICATION OF THE STRATIFICATION OF THE ATMOSPHEREATMOSPHERE


The atmosphere can be divided up The atmosphere can be divided up according to according to pressurepressure (500 (500 mbmb layer is layer is about halfway up in the atmosphere).about halfway up in the atmosphere).The atmosphere can also be divided up The atmosphere can also be divided up according to according to temperaturetemperature (which does not (which does not follow a simple relationship with height).follow a simple relationship with height).Averaging out temperature values in the Averaging out temperature values in the atmosphere, we identify atmosphere, we identify four layersfour layers..

ATMOSPHERIC LAYERSATMOSPHERIC LAYERS

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ATMOSPHERIC LAYERSATMOSPHERIC LAYERS

TroposphereTroposphere ––temperature decreases with heighttemperature decreases with heightStratosphereStratosphere ––

temperature increases with heighttemperature increases with heightMesosphereMesosphere ––

temperature decreases with heighttemperature decreases with heightThermosphereThermosphere ––temperature increases with heighttemperature increases with height

Introduction to Meteorology & Climate Fig. 1-14, p. 17


TROPOSPHERETROPOSPHERE

From the surface up to about 12km From the surface up to about 12km (varies with latitude and season (varies with latitude and season –– higher higher in Summer, and in the tropics).in Summer, and in the tropics).Temperature decreases with height Temperature decreases with height because the troposphere is heated by the because the troposphere is heated by the surface and not directly by sunlight.surface and not directly by sunlight.Almost all of what we call “weather” Almost all of what we call “weather” occurs in the troposphere.occurs in the troposphere.Contains 80% of the atmosphere’s massContains 80% of the atmosphere’s mass


STRATOSPHERESTRATOSPHEREBetween about 12km and 50km.Between about 12km and 50km.Temperature increases with height because Temperature increases with height because the the ozone layerozone layer absorbs ultraviolet light and absorbs ultraviolet light and warms up as a result.warms up as a result.Lack of mixing and turbulence.Lack of mixing and turbulence.Very little exchange occurs between the Very little exchange occurs between the stratosphere and troposphere (but it is stratosphere and troposphere (but it is important where it does).important where it does).99.9% of the atmospheric mass below the 99.9% of the atmospheric mass below the stratopausestratopause..


MESOSPHERE & THERMOSPHEREMESOSPHERE & THERMOSPHEREMesosphere between 50km and 85km.Mesosphere between 50km and 85km.

Thermosphere goes up and up and up: there Thermosphere goes up and up and up: there is no clear separation between the is no clear separation between the thermosphere and interplanetary space.thermosphere and interplanetary space.

The highest temperatures in the atmosphere The highest temperatures in the atmosphere are found in the thermosphere due to high are found in the thermosphere due to high energy radiation being absorbed by gases.energy radiation being absorbed by gases.

Ionosphere (charged gas atoms) that Ionosphere (charged gas atoms) that reflects radio waves, and aurora are here.reflects radio waves, and aurora are here.


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1. Troposphere- literally means region where air “turns over”-temperature usually decreases (on average ~6.5°C/km) with altitude

2. Stratosphere- layer above the tropopause, little mixing occurs in the stratosphere, unlike the troposphere, where “turbulent mixing” is common

3. Mesosphere- defined as the region where temperature again decreases with height.

4. Thermosphere- region with very little of the atmosphere’s mass. High energy radiation received by the thermosphere: high temperatures. Very low density (not much “heat” felt).

Tropopause

Stratopause

Mesopause



In meteorology we often refer to altitude as a certain pressure value rather than height.

The atmosphere moves mainly on constant pressure surfaces (isobaric surfaces)

850 mb ≈ 1500 m (5000 ft)700 mb ≈ 3000 m (10,000 ft)500 mb ≈ 5500 m (18000)300 mb ≈ 9000 m (30,000)


Pressure reduction to sea levelPressure reduction to sea level

ExerciseExercise


Introduction to Weather MapsIntroduction to Weather Maps


ATMOSPHERIC FRONTSATMOSPHERIC FRONTSFrontFront –– a boundary between two regions of a boundary between two regions of air that have different meteorological air that have different meteorological properties, e.g. temperature or humidity.properties, e.g. temperature or humidity.Cold frontCold front –– a region where cold air is a region where cold air is replacing warmer air.replacing warmer air.Warm frontWarm front –– a region where warm air is a region where warm air is replacing colder air.replacing colder air.Stationary frontStationary front –– a front that is not moving.a front that is not moving.Occluded frontOccluded front –– a front where warm air is a front where warm air is forced aloft.forced aloft.

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Fig. 1-15, p. 18


Fig. 9.13

WARM FRONT


Fig. 9.15

COLD FRONT


SYNOPTIC

WEATHER CHART


WEATHER PLOTTING SYMBOLSWEATHER PLOTTING SYMBOLS


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DECODING SEADECODING SEA--LEVEL PRESSURELEVEL PRESSURE

On the station model, only the last three On the station model, only the last three digits of the seadigits of the sea--level pressure are level pressure are shown.shown.Example: You see “138” written for Example: You see “138” written for pressure. To decode,pressure. To decode,

Add a 9 or a 10 to the beginning to get 9138 Add a 9 or a 10 to the beginning to get 9138 or 10138or 10138Add the decimal point between the last two Add the decimal point between the last two digits to get 913.8 or 1013.8digits to get 913.8 or 1013.8The one closest to 1000 The one closest to 1000 millibarsmillibars is the seais the sea--level pressure. In this example, the sealevel pressure. In this example, the sea--level level pressure is 1013.25 pressure is 1013.25 mbmb..


PRESSURE TENDENCYPRESSURE TENDENCY

The trend in pressure (whether it is rising or The trend in pressure (whether it is rising or falling) is important for weather forecasting.falling) is important for weather forecasting.If you see “If you see “--3” for pressure tendency, it means 3” for pressure tendency, it means that the pressure has decreased 0.3 that the pressure has decreased 0.3 millibarsmillibars in in the past 3 hours.the past 3 hours.If you see “12” for pressure tendency, it means If you see “12” for pressure tendency, it means that the pressure has increased 1.2 that the pressure has increased 1.2 millibarsmillibars in in the past 3 hours.the past 3 hours.The symbol next to the number shows how the The symbol next to the number shows how the pressure has changed (increased sharply, pressure has changed (increased sharply, increased then fell, etc.)increased then fell, etc.)


Table 1-2, p. 24

WEATHER WATCHES & WARNINGSWEATHER WATCHES & WARNINGS


METEOROLOGICAL TIMEMETEOROLOGICAL TIMEAll weather reports are All weather reports are labelledlabelled using using Coordinated Universal Time (UTC),Coordinated Universal Time (UTC),also called Greenwich Mean Time also called Greenwich Mean Time (GMT), and also denoted Zulu (Z).(GMT), and also denoted Zulu (Z).

Zulu is the time along the 0Zulu is the time along the 0ºº longitude longitude line, which runs through Greenwich.line, which runs through Greenwich.

Meteorology uses the 24 hour clock Meteorology uses the 24 hour clock which omits the use of a.m. and p.m. which omits the use of a.m. and p.m. (0900 = 9 a.m., 2100 = 9 p.m.)(0900 = 9 a.m., 2100 = 9 p.m.)


Revision: Layers of the AtmosphereRevision: Layers of the Atmosphere

Hot top: oxygen Hot top: oxygen absorbs sunlightabsorbs sunlight

Warm middle: ozone Warm middle: ozone absorbs ultraviolet (UV)absorbs ultraviolet (UV)

Warm surface: land and Warm surface: land and ocean absorb sunlightocean absorb sunlight


Study Ackerman and KnoxStudy Ackerman and Knox

Chapter 1Chapter 1Pages 12Pages 12--2222

Answer Review Questions.Answer Review Questions.

Reading Exercise

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End of Chapter 1End of Chapter 1

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Climate & Introduction to Earth System Science Meteorology & … · 2007-09-12 · 2 Introduction to Meteorology & Climate Weather Satellite Image, July 7, 2005 Introduction to Meteorology