Meteorology Part 2:Meteorology Part 2:Weather Variables Weather Variables

Earth ScienceEarth Science

Golodolinski/Black Golodolinski/Black

20092009

Part II: Weather VariablesPart II: Weather Variables

1.1. TemperatureTemperature

2.2. Air PressureAir Pressure

3.3. Relative HumidityRelative Humidity

Weather VariablesWeather Variables

1. Temperatures1. Temperatures– The measure of the The measure of the

average kinetic average kinetic energyenergy

– How fast the How fast the molecules movemolecules move

– Instrument used to Instrument used to measure temperature:measure temperature: ThermometerThermometer

– ESRT: Temperature ESRT: Temperature conversion chart on p. conversion chart on p. 1313

Measured Measured inin

°F°F FahrenheitFahrenheit

°C°C CelsiusCelsius

°K°K KelvinKelvin

1. Temperatures1. Temperatures

Shown on a weather map with:Shown on a weather map with:– Isotherms- Lines that connect places of equal Isotherms- Lines that connect places of equal

temperaturetemperature

ESRT: Temperature conversion chart ESRT: Temperature conversion chart on p. 13on p. 13

& Chart Blank p. 183& Chart Blank p. 183

ESRT: Temperature Conversion ESRT: Temperature Conversion Chart on p. 13Chart on p. 13

Chart Answers p. 183Chart Answers p. 183

ESRT: Temperature Conversion ESRT: Temperature Conversion Chart on p. 13Chart on p. 13

Temperature Chart Blank p. 183Temperature Chart Blank p. 183

ESRT: Temperature Conversion ESRT: Temperature Conversion Chart on p. 13Chart on p. 13

Temperature Chart Answers p. 183Temperature Chart Answers p. 183

Weather VariablesWeather Variables

2. Air Pressure2. Air Pressure The weight of Earth’s AtmosphereThe weight of Earth’s Atmosphere Changes depending on the temperatureChanges depending on the temperature Instrument used to measure pressure:Instrument used to measure pressure:

– BarometerBarometer

Measured in Measured in inchesinches and and milibarsmilibars

2. Air Pressure2. Air Pressure

Shown on a weather Shown on a weather map with:map with:– Isobars- Lines that Isobars- Lines that

connect places of connect places of equal barometric equal barometric pressurespressures

2. Air Pressure2. Air Pressure

Mercury barometerMercury barometer– As the air pressure pushes on As the air pressure pushes on

the surface of the mercury in the surface of the mercury in the dish, the mercury travels up the dish, the mercury travels up the tube.the tube.

– As pressure increases, the As pressure increases, the mercury rises in the tube.mercury rises in the tube. Cool air sinks- causes higher Cool air sinks- causes higher

pressurepressure– As the pressure decreases, the As the pressure decreases, the

mercury sinks out of the tube.mercury sinks out of the tube. Warm air rises- causes lower Warm air rises- causes lower

pressurepressure

ESRT: ESRT: Pressure Pressure

Conversion Conversion Chart p. 13Chart p. 13

ESRT: Pressure Conversion Chart p. ESRT: Pressure Conversion Chart p. 1313

Blank Chart p. 184Blank Chart p. 184

ESRT: Pressure Conversion Chart p. ESRT: Pressure Conversion Chart p. 1313

Answer Chart p. 184Answer Chart p. 184

2. Air Pressure2. Air Pressure

State the relationship State the relationship between altitude and air between altitude and air pressure.pressure.– As the altitude increases, As the altitude increases,

the pressure the pressure decreasesdecreases

Draw the relationship on Draw the relationship on the graph.the graph.

Weather VariablesWeather Variables3. Relative Humidity3. Relative Humidity

– A ratio between the amount of moisture is in the A ratio between the amount of moisture is in the atmosphere and how much moisture the atmosphere and how much moisture the atmosphere can holdatmosphere can hold

– Measured in Measured in %%– When the air is holding as much water vapor as it can, When the air is holding as much water vapor as it can,

the air is the air is saturated. saturated. When saturated, warm air contains more water vapor than cold saturated air.

– When the air is saturated, the relative humidity is When the air is saturated, the relative humidity is 100%100%

To summarize, when the water-vapor content of air remains constant, lowering air temperature causes an increase in relative humidity, and raising air temperature causes a decrease in relative humidity.

3. Relative Humidity3. Relative Humidity

Temperature & Relative Temperature & Relative HumidityHumidity– The warmer the temperature The warmer the temperature

is, the more moisture it can is, the more moisture it can holdhold

State the relationship between State the relationship between temperature and relative temperature and relative humidity:humidity:– As the temperature increases, As the temperature increases,

relative humidity relative humidity decreasesdecreases Draw the relationship on the Draw the relationship on the

graph.graph.

3. Relative Humidity- 3. Relative Humidity- InsturementsInsturements

3. Relative Humidity3. Relative Humidity

Dew Point TemperatureDew Point Temperature– The temperature in which the air is saturatedThe temperature in which the air is saturated– 100% relative humidity100% relative humidity

Determining Relative Humidity and Determining Relative Humidity and Dew Point TemperaturesDew Point Temperatures

Dry bulbDry bulb– Air temperatureAir temperature

Wet bulbWet bulb– Temperature an air parcel cooled by Temperature an air parcel cooled by

evaporation of water (wet cloth)evaporation of water (wet cloth) When given the wet bulb and dry bulb When given the wet bulb and dry bulb

temperatures, you can determine the dew temperatures, you can determine the dew point temperature and relative by follow point temperature and relative by follow directions provided and using ESRT p. 12directions provided and using ESRT p. 12

ESRT: Dew Point Temp. p. 12ESRT: Dew Point Temp. p. 12

ESRT: Relative Humidity p. 12ESRT: Relative Humidity p. 12

Example 1 p. 186Example 1 p. 186

Example 2 p. 186Example 2 p. 186

p. 187 chart and #1-5

Practice Dew Point & Relative Humidity p. 187Practice Dew Point & Relative Humidity p. 187

Practice Dew Point & Relative Humidity p. Practice Dew Point & Relative Humidity p. 187 Answers187 Answers

Practice Dew Point & Relative Humidity p. Practice Dew Point & Relative Humidity p. 187 187 #1-5#1-5

Condensation Condensation – Gas to liquidGas to liquid– Change of phase from Change of phase from

water vapor water vapor (gas)(gas) to to liquid vapor liquid vapor (water)(water)

– Examples:Examples: Water on cold glass of Water on cold glass of

water, water on mirror water, water on mirror after a shower, dew on after a shower, dew on grass, fog, cloudsgrass, fog, clouds

– EvaporationEvaporation Liquid to gasLiquid to gas

3 Things Needed for Condensation 3 Things Needed for Condensation to Occurto Occur

1.1. Water vapor must be presentWater vapor must be present

2.2. Air must be separated (relative humidity Air must be separated (relative humidity 100%)100%)

3.3. Condensation nuclei (ex. dust particles)Condensation nuclei (ex. dust particles)

Density of AirDensity of Air

Warm air rises because it is less denseWarm air rises because it is less dense Cold air sinks because it is more denseCold air sinks because it is more dense

Formation of CloudsFormation of Clouds

Warm moist air risesWarm moist air rises Air expands and cools due to the dew Air expands and cools due to the dew

pointpoint Air becomes saturatedAir becomes saturated Water droplets form on dust particlesWater droplets form on dust particles Clouds consist of water droplets and ice Clouds consist of water droplets and ice

crystalscrystals

Cloud ClassificationCloud Classification

Adiabatic CoolingAdiabatic Cooling

The cooling of a parcel of air as it rises The cooling of a parcel of air as it rises through the atmospherethrough the atmosphere

Dry adiabatic lapse rateDry adiabatic lapse rate– rate of cooling or heating that applies only to

unsaturated air.– dry air cools fasterdry air cools faster

Wet adiabatic lapse rateWet adiabatic lapse rate– rate of adiabatic temperature change in

saturated air.– moist air cools slowermoist air cools slower

Cloud Formation by Cloud Formation by Adiabatic CoolingAdiabatic Cooling

PrecipitationPrecipitation

Cloud particles Cloud particles (any form of water)(any form of water) too too heavy to remain suspended in the air fall heavy to remain suspended in the air fall to Earth from a cloudto Earth from a cloud– Examples: rain, hail, sleet, snow, freezing Examples: rain, hail, sleet, snow, freezing

rainrain– What does precipitation do for the environment? What does precipitation do for the environment?

Cleans the airCleans the air

– ESRT p. 13 Present WeatherESRT p. 13 Present Weather

Forms of PrecipitationForms of Precipitation The type of precipitation that reaches Earth’s

surface depends on the temperature profile in the lower few kilometers of the atmosphere.

Rain & Snow In meteorology, the term rain means drops of water that

fall from a cloud and have a diameter of at least 0.5 mm. At very low temperatures (when the moisture content of

air is low) light fluffy snow made up of individual six-sided ice crystals forms.

Sleet is the fall of clear-to-translucent ice. Hail is produced in cumulonimbus clouds.

ESRT p. 13 Present WeatherESRT p. 13 Present Weather

WindWind

The horizontal movement of air The horizontal movement of air Caused by the uneven heating of Earth’s Caused by the uneven heating of Earth’s

surfacesurface Differences in air temperature cause Differences in air temperature cause

differences in air pressuredifferences in air pressure The greater the difference in air pressure, The greater the difference in air pressure,

the faster the windthe faster the wind

WindWind

Named by the direction in which they Named by the direction in which they come from come from – Ex. North wind comes from the NorthEx. North wind comes from the North

Isobars Isobars – Connect places of equal barometric Connect places of equal barometric

pressure on a weather mappressure on a weather map

Wind InstrumentsWind Instruments

AnemometerAnemometer– Measures wind speedMeasures wind speed

Wind vaneWind vane– Determines wind Determines wind

directiondirection

Sea BreezeSea Breeze

Water heats up slower Water heats up slower than land:than land:– High specific heatHigh specific heat– Cooler temperaturesCooler temperatures– Air sinksAir sinks– *HIGH pressure**HIGH pressure*

Land heats up faster Land heats up faster than water:than water:– Low specific heatLow specific heat– Warmer temperaturesWarmer temperatures– Air risesAir rises– *LOW pressure**LOW pressure*

Land BreezeLand Breeze

Water cools down Water cools down slower than land (stays slower than land (stays warmer)warmer)– High specific heatHigh specific heat– Warmer temperatures Warmer temperatures

at nightat night– Air risesAir rises

Land cools down faster Land cools down faster than waterthan water– Low specific heatLow specific heat– Cooler temperatures at Cooler temperatures at

nightnight– Air sinksAir sinks

Sea and Land BreezesSea and Land Breezes

Coriolis EffectCoriolis Effect The deflection of winds and ocean currents The deflection of winds and ocean currents

caused by the rotation of Earthcaused by the rotation of Earth Deflection is to the right in the Northern Deflection is to the right in the Northern

Hemisphere and to the left in the Southern Hemisphere and to the left in the Southern HemisphereHemisphere

Weather Factors Associated with Weather Factors Associated with Different Pressure AreasDifferent Pressure Areas

High PressureHigh Pressure– Cool/ cold airCool/ cold air– Air sinks/ goes downAir sinks/ goes down– Air moves outwardAir moves outward– ClockwiseClockwise

– No cloudsNo clouds– No precipitationNo precipitation

Low PressureLow Pressure– Warm airWarm air– Air risesAir rises– Air moves inwardAir moves inward– Counter clockwiseCounter clockwise

– CloudsClouds– Precipitation likelyPrecipitation likely

ESRT: Planetary Winds p. 14ESRT: Planetary Winds p. 14

Planetary WindsPlanetary Winds

p. 191 Weather Changes- adobe

Weather Changes p. 191Weather Changes p. 191

Weather ChangesWeather Changes

Air MassesAir Masses

Large region of the atmosphere with Large region of the atmosphere with uniform temperature and humidityuniform temperature and humidity

ESRT p. ESRT p. 1313: Air Masses: Air Masses

Air Masses TableAir Masses Table

Air Masses MapAir Masses Map

FrontsFronts

The boundary between 2 air massesThe boundary between 2 air masses ESRT p. ESRT p. 1313 Front Symbols Front Symbols

Cold FrontCold Front

Cold air pushes the Cold air pushes the warm, moist air upwardwarm, moist air upward

Cold air is located Cold air is located behind the frontbehind the front

The greater the The greater the differences in differences in temperatures, the more temperatures, the more likely there will be a likely there will be a major stormmajor storm

Usually pass quicklyUsually pass quickly Brings colder but clear Brings colder but clear

weather conditionsweather conditions

Warm FrontWarm Front Warm air gently rolls Warm air gently rolls

over the colder airover the colder air Warm air is located Warm air is located

behind the frontbehind the front Conditions are usually Conditions are usually

cloudy and rainy for cloudy and rainy for several hoursseveral hours

Usually pass slowlyUsually pass slowly Brings warmer but Brings warmer but

rainy weather rainy weather conditionsconditions

Occluded FrontOccluded Front

Occurs when a cold Occurs when a cold air mass overtakes a air mass overtakes a warm mass and warm mass and overtakes another overtakes another cold air masscold air mass

Precipitation is Precipitation is possible but not possible but not definitedefinite

Very slight Very slight temperature changetemperature change

Stationary FrontStationary Front Notice no arrows to Notice no arrows to

show direction in the show direction in the weather map symbolsweather map symbols

Stationary means the Stationary means the front is not movingfront is not moving

Final direction of the Final direction of the movement is difficult to movement is difficult to predictpredict

Winds are blowing in Winds are blowing in opposite directions on opposite directions on each side of the fronteach side of the front

Clouds can last for daysClouds can last for days

Fronts are usually associated Fronts are usually associated with…with…

CloudsClouds PrecipitationPrecipitation Change in temperatureChange in temperature Change in wind directionChange in wind direction

p.195 Station Models- Adobe

Station ModelsStation Models

On a station model, On a station model, barometric pressure is barometric pressure is ALWAYS written in a ALWAYS written in a three-digit formatthree-digit format

Converting from Converting from millibars:millibars:– Drop the 9 or 10 in the Drop the 9 or 10 in the

front of the number and front of the number and loose the decimal pointloose the decimal point

MillibarsMillibars Station Station ModelModel

1009.3 mb1009.3 mb 093093

984.2 mb984.2 mb

1024.2 mb1024.2 mb

Station ModelsStation Models

Converting from the station Converting from the station model format to milibarsmodel format to milibars

First:First:– If the first number on the If the first number on the

station model is station model is 0-40-4, place a , place a 1010 in front of the number in front of the number

– If the first number on the If the first number on the station model is station model is 5-95-9, place a , place a 9 9 in front of the numberin front of the number

Second:Second:– Place a decimal point Place a decimal point

between the last 2 numbersbetween the last 2 numbers

Station Station ModelModel

MillibarsMillibars

146 146 1014.6 mb1014.6 mb

457457

986986

p. 195

ESRT: Weather Map SymbolsESRT: Weather Map Symbols

Weather StationsWeather Stations

Draw a weather station using the Draw a weather station using the following information:following information:

Need to know: Need to know: Dew Point & Air TemperatureDew Point & Air Temperature

The closer the air temperature is to the dew The closer the air temperature is to the dew point temperature, the greater the chance point temperature, the greater the chance for precipitation.for precipitation.

Determining Weather Station ValuesDetermining Weather Station Values

6 stations on p. 197; Weather Map practice p. 199-203 #1-31; More questions p. 204-207 #1-22