10.2 Energy Transfer in the Atmosphere10.2 Energy Transfer in the Atmosphere

Originally, Earth’s Originally, Earth’s atmosphere had no atmosphere had no oxygen.oxygen. Scientists think it first Scientists think it first

came from the came from the breakdown of water by breakdown of water by sunlight, then from sunlight, then from photosynthesis by photosynthesis by plants.plants.

The density of the The density of the atmosphere decreases atmosphere decreases with altitude.with altitude.

The composition of Earth’s atmosphere

The Layers of the AtmosphereThe Layers of the Atmosphere

1)The T1)The Troposphereroposphere: :

- closest to Earth’s surface- closest to Earth’s surface

- highest density layer because - highest density layer because all other layers compress itall other layers compress it

- contains almost all the water - contains almost all the water vapour in the atmosphere.vapour in the atmosphere. so, this is where most so, this is where most

weather takes place.weather takes place. 22ndnd warmest layer warmest layer

See pages 438 - 439

The The Stratosphere:Stratosphere: the second layerthe second layer warming from –55ºC as altitude warming from –55ºC as altitude

increasesincreases The air is cold, dry, and The air is cold, dry, and

cloudless.cloudless. Strong, steady winds, planes Strong, steady winds, planes

often fly here to avoid turbulent often fly here to avoid turbulent troposphere.troposphere.

The ozone layer is found here, The ozone layer is found here, which blocks harmful UV which blocks harmful UV radiation.radiation.

The The mesospheremesosphere: (3: (3rdrd layer) layer)Temperatures are as low as –100ºCTemperatures are as low as –100ºCThis layer is where space debris This layer is where space debris burns up when it begins to hit burns up when it begins to hit particles.particles.

The The thermospherethermosphere: (4: (4thth layer) layer)Temperatures can reach +1500ºC to Temperatures can reach +1500ºC to +3000ºC because of radiation from +3000ºC because of radiation from the sunthe sunThis is where the Northern Lights, This is where the Northern Lights, aurora borealisaurora borealis, are found., are found.

The The exosphereexosphere: (5: (5thth layer) layer) where the atmosphere merges with where the atmosphere merges with outer space.outer space.

The layers of Earth’s atmosphere

The Upper AtmosphereThe Upper Atmosphere

Radiation and Conduction in the AtmosphereRadiation and Conduction in the AtmosphereThermal energy mostly comes from the Sun.Thermal energy mostly comes from the Sun. Most thermal energy is transferred near the equator, Most thermal energy is transferred near the equator,

which receives a more direct source of solar radiation.which receives a more direct source of solar radiation. InsolationInsolation = amount of solar radiation = amount of solar radiation

an area receives, measured in W/man area receives, measured in W/m22

decreases with dust, smoke, pollution,decreases with dust, smoke, pollution,

etc. or if the angle of incidence of the etc. or if the angle of incidence of the

solar radiation is too great.solar radiation is too great. Solar radiation does not heat Solar radiation does not heat

the atmosphere directly.the atmosphere directly.Earth’s surface absorbs solar radiation, heats up, then Earth’s surface absorbs solar radiation, heats up, then

radiates the thermal energy into the atmosphere.radiates the thermal energy into the atmosphere.

Convection currents in the air spread the thermal energy around.Convection currents in the air spread the thermal energy around.

Angle of incidence

The Radiation BudgetThe Radiation BudgetThe radiation budget is used to explain where The radiation budget is used to explain where all of the solar radiation that reaches Earth all of the solar radiation that reaches Earth actually goes.actually goes. Earth’s radiation budget = heat gained – heat lostEarth’s radiation budget = heat gained – heat lost Of the of the solar radiation that reaches Earth, 15 Of the of the solar radiation that reaches Earth, 15

percent is reflected by clouds back into space, 7 percent is reflected by clouds back into space, 7 percent is reflected by particles back into space, percent is reflected by particles back into space, 20 percent is absorbed by clouds and the 20 percent is absorbed by clouds and the atmosphere, and 58 percent reaches Earth’s atmosphere, and 58 percent reaches Earth’s surfacesurface

9 percent of this amount is reflected back out into space by 9 percent of this amount is reflected back out into space by Earth’s surfaceEarth’s surface

23 percent drives the water cycle, 7 percent creates wind, and 23 percent drives the water cycle, 7 percent creates wind, and 19 percent is re-radiated from Earth’s surface.19 percent is re-radiated from Earth’s surface.

The Radiation Budget and AlbedoThe Radiation Budget and Albedo

AlbedoAlbedo refers to the amount of energy reflected refers to the amount of energy reflected by a surface.by a surface. Light-coloured surfaces (snow, sand) have a high Light-coloured surfaces (snow, sand) have a high

albedo and reflect energy.albedo and reflect energy. Dark-coloured surfaces (soil, water) have a low Dark-coloured surfaces (soil, water) have a low

albedo and absorb energy.albedo and absorb energy.

What Is Weather?What Is Weather?

WeatherWeather is atmosphere conditions. is atmosphere conditions. related to the transfer of thermal energy.related to the transfer of thermal energy.

Atmospheric pressureAtmospheric pressure is determined is determined by the number of molecules and by the number of molecules and how fast they are moving.how fast they are moving. measured with a barometer measured with a barometer measured in kilopascals (kPa) measured in kilopascals (kPa)

Ex. our ears pop with pressure changeEx. our ears pop with pressure change as you increase altitude, the pressure drops.as you increase altitude, the pressure drops. Warm air is lighter and less dense than cool air Warm air is lighter and less dense than cool air

and so warm air has a lower pressure than cool air.and so warm air has a lower pressure than cool air.

Atmospheric pressure exerts force on you from

all directions.

Humid air (air with more water Humid air (air with more water vapour) has lower pressure than vapour) has lower pressure than dry air.dry air. Specific humidity = the total amount Specific humidity = the total amount

of water vapour in the air.of water vapour in the air.Dew point = the temperature where no Dew point = the temperature where no more water vapour can be held by airmore water vapour can be held by air

Relative humidity = the percentage of Relative humidity = the percentage of the air that is currently holding water the air that is currently holding water vapourvapour

45 percent relative humidity means that 45 percent relative humidity means that the air is holding 45 percent of the water the air is holding 45 percent of the water vapour it could before reaching its dew vapour it could before reaching its dew point.point.

Convection in the AtmosphereConvection in the Atmosphere

WindWind is the movement of air from higher is the movement of air from higher pressure to lower pressure.pressure to lower pressure. An An air massair mass is a large body of air with similar is a large body of air with similar

temperature and humidity throughout.temperature and humidity throughout.takes on the conditions of the weather below.takes on the conditions of the weather below.

can be as large as an entire province or even larger.can be as large as an entire province or even larger.

High pressure systems form when an air High pressure systems form when an air mass cools.mass cools. This usually occurs over cold This usually occurs over cold

water or land.water or land. Winds blow clockwise around Winds blow clockwise around

the centre of the system.the centre of the system.

Low pressure systems form when an air Low pressure systems form when an air mass warms.mass warms. This usually occurs over This usually occurs over

warm water or land.warm water or land. Winds blow counterclockwise Winds blow counterclockwise

around the centre of the system.around the centre of the system. Lows usually bring wet weather.Lows usually bring wet weather.

Prevailing WindsPrevailing Windsare winds that are typical for a location.are winds that are typical for a location. Winds in B.C. usually blow in from the ocean.Winds in B.C. usually blow in from the ocean. Precipitation falls as air is forced up the mountains Precipitation falls as air is forced up the mountains So air gets drier as it moves inlandSo air gets drier as it moves inland Dry air rushes down the far side of the mountains Dry air rushes down the far side of the mountains

into the prairies.into the prairies.

See pages 448 - 449

The prevailing winds off British Columbia’s coast, crossing into Alberta.

The Coriolis EffectThe Coriolis EffectWinds move from higher pressure to lower Winds move from higher pressure to lower pressure.pressure. In a simple model, air would warm in the tropics and rise.In a simple model, air would warm in the tropics and rise. Cooler air from the north wouldCooler air from the north would

rush in below to fill the empty spot.rush in below to fill the empty spot. The warm air at higher altitudes wouldThe warm air at higher altitudes would

move north to replace the cooler air.move north to replace the cooler air. This occurs at several latitudes as This occurs at several latitudes as

we move north.we move north.

As Earth rotates, these winds are “bent” As Earth rotates, these winds are “bent” clockwise = clockwise = Coriolis effectCoriolis effect The equator moves much more quickly than do the poles.The equator moves much more quickly than do the poles.

Jet StreamsJet StreamsStrong winds occur in areas between high and Strong winds occur in areas between high and low pressure systems.low pressure systems. The boundaries between the global wind systems The boundaries between the global wind systems

have very strong winds.have very strong winds. In the upper troposphere, between warm and cool In the upper troposphere, between warm and cool

air, are the jet streams.air, are the jet streams.The polar jet stream can move at 185 km/h for thousands The polar jet stream can move at 185 km/h for thousands of kilometres.of kilometres.

Planes flying east across Canada “ride” the jet stream Planes flying east across Canada “ride” the jet stream and avoid it flying west.and avoid it flying west.

Local Winds, and FrontsLocal Winds, and Fronts

Local winds arise and are influenced by Local winds arise and are influenced by local geography.local geography. In British Columbia, sea breezes blow inland In British Columbia, sea breezes blow inland

when the land warms in the morning and when the land warms in the morning and outward when the land cools in the evening.outward when the land cools in the evening.

A front is a boundary between two A front is a boundary between two different air masses.different air masses. Cold air forces warm air to rise, soCold air forces warm air to rise, so

fronts usually bring precipitation.fronts usually bring precipitation.

Extreme WeatherExtreme Weather

Air masses often have very large amounts of Air masses often have very large amounts of thermal energy.thermal energy. Extreme weather can arise as this energy is Extreme weather can arise as this energy is

released.released. Thunderstorms occur when warm air rises and Thunderstorms occur when warm air rises and

water condenses (which releases even more water condenses (which releases even more energy), building the thunderhead even higher.energy), building the thunderhead even higher.

Static energy can be built up and released as lightning.Static energy can be built up and released as lightning.Sea breezes in the tropics and energetic cold (and Sea breezes in the tropics and energetic cold (and even warm) fronts can cause thunderstorms.even warm) fronts can cause thunderstorms.

See pages 452 - 453

Tornadoes Vs. HurricanesTornadoes Vs. HurricanesTornadoes form when thunderstorms meet fast Tornadoes form when thunderstorms meet fast horizontal winds.horizontal winds. A “funnel” of rotating air may form, which sometimes A “funnel” of rotating air may form, which sometimes

extends all the way to the ground with winds of up to 400 extends all the way to the ground with winds of up to 400 km/h.km/h.

The tropics, with their intense heat, can often have The tropics, with their intense heat, can often have severe weather.severe weather. Large masses of warm, moist air rise quickly and cool air Large masses of warm, moist air rise quickly and cool air

rushes in.rushes in. Air rotates counterclockwise in the northern hemisphere, Air rotates counterclockwise in the northern hemisphere,

clockwise in the south. clockwise in the south. Hurricanes = tropical cyclones = typhoonsHurricanes = tropical cyclones = typhoons

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