Heating the AtmosphereHeating the Atmosphere

Electromagnetic WavesElectromagnetic Waves

The sun is the ultimate source of The sun is the ultimate source of energy that creates our weather. energy that creates our weather.

You know that the sun emits light and You know that the sun emits light and heat as well as the ultraviolet rays heat as well as the ultraviolet rays that cause a sunburn. that cause a sunburn.

Electromagnetic WavesElectromagnetic Waves

These forms of energy are only a part These forms of energy are only a part of a larger array of energy called the of a larger array of energy called the electromagnetic spectrum.electromagnetic spectrum.

All radiation, whether X-rays, radio All radiation, whether X-rays, radio

waves or infrared waves, travel waves or infrared waves, travel through the vacuum of space at through the vacuum of space at 300,000 kilometers per second.300,000 kilometers per second.

Only 7% of the light Only 7% of the light energy received by energy received by the earth is visible the earth is visible light.light.

Electromagnetic waves are classifiedElectromagnetic waves are classified

by their by their wavelengths; wavelengths; the distance the distance from the from the crest of one crest of one wave to the wave to the crest of the crest of the next wave.next wave.

Heat transferHeat transfer

Three mechanisms of energy transfer Three mechanisms of energy transfer as heat are as heat are

——Conduction Conduction ——Convection Convection ——Radiation Radiation

All three processes happen All three processes happen simultaneously in our atmosphere. simultaneously in our atmosphere.

These mechanisms work to transfer These mechanisms work to transfer energy between Earth’s surface (both energy between Earth’s surface (both land and water) and the atmosphere. land and water) and the atmosphere.

Heat transferHeat transfer

ConductionConduction – the movement of heat – the movement of heat from molecule to molecule; through from molecule to molecule; through molecular activitymolecular activity• Heat flows from the higher temperature Heat flows from the higher temperature

matter to the lower temperature mattermatter to the lower temperature matter• Metals are good conductors Metals are good conductors

of heat; air is a poor of heat; air is a poor

conductor of heat.conductor of heat.

Because air is a poor conductor, Because air is a poor conductor, conduction is important only conduction is important only between between Earth’s surface and air Earth’s surface and air directly in contact with the directly in contact with the surface. surface.

For our atmosphere, conduction is For our atmosphere, conduction is the the leastleast importantimportant mechanism of mechanism of heat transfer.heat transfer.

Heat transferHeat transfer

Heat transferHeat transfer

ConvectionConvection – the movement of heat – the movement of heat by circulation within a substanceby circulation within a substance

Much of the heat transfer that occurs Much of the heat transfer that occurs in the atmosphere is convectionin the atmosphere is convection

Convection takes place in fluids Convection takes place in fluids where the molecules can move where the molecules can move freely.freely.

The atmosphere behaves like a fluidThe atmosphere behaves like a fluid

Heat transferHeat transfer example of convection: a pot of example of convection: a pot of

boiling waterboiling water

RadiationRadiation – the release and transfer – the release and transfer of energy in wavelengths of heat and of energy in wavelengths of heat and light through space. light through space.

Solar Energy reaches the Earth from Solar Energy reaches the Earth from the sun by radiationthe sun by radiation

There are actually 4 laws that There are actually 4 laws that govern radiation….govern radiation….

Heat transferHeat transfer

1: 1: All objects, at any temperature, All objects, at any temperature, emit radiant energy. emit radiant energy. Not only hot objects like the sun, Not only hot objects like the sun, but colder objects like the Earth but colder objects like the Earth (including it’s polar ice caps) (including it’s polar ice caps) continuously emit energy.continuously emit energy.

2. Hotter objects 2. Hotter objects radiate more radiate more total energy total energy “per unit area” “per unit area” than colder than colder objects do.objects do.

3. The hottest 3. The hottest radiating bodies radiating bodies produce the produce the shortest shortest wavelengths of wavelengths of maximum maximum radiationradiation

The sun, at 6000C, The sun, at 6000C, radiates at .5 radiates at .5 micrometers.micrometers.

When radiation strikes an When radiation strikes an object, there are usually three object, there are usually three

different results.different results.

1. Some energy is absorbed by the object. 1. Some energy is absorbed by the object. When radiant energy is absorbed, it is When radiant energy is absorbed, it is converted to heat and causes a converted to heat and causes a temperature increase. temperature increase.

Like what??Like what??

When radiation strikes an When radiation strikes an object, there are usually three object, there are usually three

different resultsdifferent results 2. Substances such as water and air are 2. Substances such as water and air are

transparent to certain wavelengths of transparent to certain wavelengths of radiation. These substances transmit the radiation. These substances transmit the radiant energy. radiant energy.

In other words – Radiation goes THROUGH In other words – Radiation goes THROUGH the objectthe object

When radiation strikes an When radiation strikes an object, there are usually three object, there are usually three

different resultsdifferent results 3. Some radiation may bounce off the object 3. Some radiation may bounce off the object

without being absorbed or transmitted.without being absorbed or transmitted.

Thus being scatteredThus being scattered

This This scattering is scattering is why the sky why the sky is blue…is blue…

… … and the sunsets and the sunsets are often redare often red

(what do you think is (what do you think is the meaning of the meaning of “Red sky at night, “Red sky at night, sailors’ delight; red sailors’ delight; red sky in the morning, sky in the morning, sailors’ take sailors’ take warning”warning”

Heat Budget of the AtmosphereHeat Budget of the Atmosphere

When it reaches the Earth, some is reflected When it reaches the Earth, some is reflected back to space by clouds, some is absorbed back to space by clouds, some is absorbed by the atmosphere, and some is absorbed by the atmosphere, and some is absorbed at the Earth's surface. at the Earth's surface.

Since the Earth is much cooler than the Sun, Since the Earth is much cooler than the Sun, its radiating energy is much weaker (long its radiating energy is much weaker (long wavelength) infrared energy.wavelength) infrared energy.

Heat energy from the earth can be trapped by Heat energy from the earth can be trapped by clouds leading to higher temperatures as clouds leading to higher temperatures as compared to nights with clear skies.compared to nights with clear skies.

The air is not allowed The air is not allowed to cool as much with to cool as much with cloudy skies. cloudy skies.

Under Under partlypartly cloudy cloudy skies, some heat is skies, some heat is allowed to escape allowed to escape and some remains and some remains trapped. trapped.

Clear skies allow for Clear skies allow for the most heat to the most heat to escape & cooling to escape & cooling to take place.take place.

About 50% of solar energy reaches About 50% of solar energy reaches the surface and is absorbed.the surface and is absorbed.

Most of THIS energy is reradiated.Most of THIS energy is reradiated. The atmosphere absorbs the longer The atmosphere absorbs the longer

wavelengthswavelengths Larger molecules, like water vapor Larger molecules, like water vapor

and COand CO22, absorb the energy, absorb the energy This energy is transformed into This energy is transformed into

molecular motion – rise in molecular motion – rise in temperaturetemperature

Simplified diagram of the heating of Simplified diagram of the heating of the atmospherethe atmosphere

Albedo (Al-bee-dough)

The percent of radiation returning from a surface compared to that which strikes it

When an object reflects most of the light that hits it, it looks bright and it has a high albedo. 

When an object absorbs most of the light that hits it, it looks dark.   Dark objects have low albedos.

Clouds’ albedo is near 60% Snow’s albedo is up to 95 percent Water’s albedo is (on average) about

10% Average albedo for earth and clouds

is about 30%

Conditions of the AirConditions of the Air

Temperature – amount of hotness or coldness amount of hotness or coldness relative to something elserelative to something else

•Thermometer – an instrument that measures an instrument that measures relative hotness or coldnessrelative hotness or coldness•Dew Point temperature – The temperature at The temperature at which air becomes saturatedwhich air becomes saturated•Isotherm – a line connecting places with equal a line connecting places with equal temperature on a weather maptemperature on a weather map

Temperature scales:Temperature scales:1°C = 1.8°F or 1°F = 5/9 ° C1°C = 1.8°F or 1°F = 5/9 ° C

Celsius to Fahrenheit and Fahrenheit to Celsius

FormulaFormula

°C  x  9/5 + 32 = °F°C  x  9/5 + 32 = °F

(°F  -  32)  x  5/9 = °C(°F  -  32)  x  5/9 = °C

For Example For Example

Convert 37°C to FahrenheitConvert 37°C to Fahrenheit..37°C x  9/5 + 32 = 98.6°F37°C x  9/5 + 32 = 98.6°F

OROR37°C x 937°C x 9 + 32 = 98.6°F  + 32 = 98.6°F 

5  5  Convert 98.6°F to CelsiusConvert 98.6°F to Celsius..

(98.6°F  -  32)  x  5/9 = 37°C(98.6°F  -  32)  x  5/9 = 37°COROR

((98.6°F - 3298.6°F - 32) x 5 = 37°C ) x 5 = 37°C  99

Conditions of the Air Conditions of the Air (cont.)(cont.)Air pressure - Air pressure - the downward pressure exerted by the downward pressure exerted by

the weight of the overlying atmosphere or the the weight of the overlying atmosphere or the “weight” of the atmosphere per unit AREA. “weight” of the atmosphere per unit AREA.

BarometerBarometer – an instrument used to measure air – an instrument used to measure air pressurepressure

Measured in inches of Measured in inches of mercury in a columnmercury in a column Or millibars (metric Or millibars (metric conversion)conversion) Average air pressure Average air pressure at sea level is 1013 millibarsat sea level is 1013 millibars

What do you notice about the What do you notice about the relationship between air pressure relationship between air pressure and volume?and volume?

What do you notice about the relationship What do you notice about the relationship between air pressure and temperature?between air pressure and temperature?

What do you notice about the What do you notice about the relationship between volume relationship between volume and temperature?and temperature?

Pressure depicted on a weather Pressure depicted on a weather mapmap

Isobars – Isobars – lines con-lines con-necting necting points of points of equal equal pressurepressure

Isobars on the ‘vertical’Isobars on the ‘vertical’

Note: the density of molecules close to the surfaceNote: the density of molecules close to the surface

Measurement of the Measurement of the AtmosphereAtmosphere

The condition(s) The condition(s) of the of the atmosphere is atmosphere is measured by the measured by the radiosonderadiosonde

A radiosonde is a small instrument A radiosonde is a small instrument package tethered to a weather package tethered to a weather balloon.balloon.• take a vertical profile of the atmosphere take a vertical profile of the atmosphere

as the balloon ascends to altitudes up to as the balloon ascends to altitudes up to 115,000 feet. 115,000 feet.

• the data is relayed by radio transmitter the data is relayed by radio transmitter to a computer at the surfaceto a computer at the surface

Launch Launch of a of a weather weather balloon balloon off an off an aircraft aircraft carriercarrier

photo shows the weather balloon photo shows the weather balloon bursting at 99,712 feetbursting at 99,712 feet

http://www.brothers-brick.com/2008/08/06/mindstorms-nxt-fans-launch-lego-into-space-via-weather-balloon/

Synoptic MapSynoptic Map

Station modelsStation models – group of symbols – group of symbols depicting weather conditionsdepicting weather conditions

IsobarIsobar – line of equal pressure – line of equal pressure

a.a. show locations of High or Low show locations of High or Low pressurespressures

b.b. close lines mean strong winds close lines mean strong winds

c.c. lines far apart mean gentle winds lines far apart mean gentle winds

Station ModelStation Model

how how meteorologists meteorologists can put a lot of can put a lot of information in a information in a small areasmall area

Water in the atmosphereWater in the atmosphereWater VaporWater Vapor

HumidityHumidity – the amount of water – the amount of water vapor in the airvapor in the air

Relative humidityRelative humidity – the actual – the actual amount of water vapor in the air amount of water vapor in the air compared to the greatest amount the compared to the greatest amount the air can holdair can hold

Water in the atmosphereWater in the atmosphereWater VaporWater Vapor

SaturatedSaturated – to be completely filled – to be completely filled with water vaporwith water vapor

PsychrometerPsychrometer – an instrument to – an instrument to measure relative humiditymeasure relative humidity

HygrometerHygrometer – an instrument used to – an instrument used to measure the air’s humidity measure the air’s humidity

PrecipitationPrecipitationwater or ice that condenses in the air water or ice that condenses in the air

and falls to the ground as:and falls to the ground as: RainRain- liquid water that falls to the ground- liquid water that falls to the ground SnowSnow - ice crystal flakes; - ice crystal flakes; water vapor in water vapor in

the atmosphere that froze into ice crystals the atmosphere that froze into ice crystals and falls to the ground in the form of and falls to the ground in the form of flakes flakes

SleetSleet -partially melted grains of ice -partially melted grains of ice HailHail - pellets made of layers of ice and - pellets made of layers of ice and

snowsnow Freezing rainFreezing rain – rain that freezes into ice as – rain that freezes into ice as

it hits the groundit hits the ground

Weather AdvisoriesWeather Advisories

Weather WATCHWeather WATCH – predictions about – predictions about approaching severe weatherapproaching severe weather

Weather WARNINGWeather WARNING – specific severe – specific severe weather conditions have been weather conditions have been actually observed by a person or actually observed by a person or verified by a computerverified by a computer

http://www.sleepingdogstudios.com/Network/Earth%20Science/ES_17.2_files/frame.htmhttp://www.sleepingdogstudios.com/Network/Earth%20Science/ES_17.2_files/frame.htm