Climate and Climate and WeatherWeather

The lower atmosphere - compositionThe lower atmosphere - composition

HistoricallyHistorically– H2, CH4, NH3, H20, H2, CH4, NH3, H20,

etc.etc. CurrentlyCurrently

– 78% N78% N22, 21% O, 21% O22, 1% , 1% Ar, .038% COAr, .038% CO22

– varying amounts of Hvarying amounts of H22O O vapor (1-4%)vapor (1-4%)

– Oxygen added by Oxygen added by action of organisms action of organisms (which?)(which?)

The Atmosphere – its layersThe Atmosphere – its layers

Troposphere Troposphere – extends from surface to 17kmextends from surface to 17km– 75% of total mass of atmosphere75% of total mass of atmosphere– where weather occurs, air where weather occurs, air

currents etc.currents etc.– highest atmospheric pressurehighest atmospheric pressure– temperature decreases with temperature decreases with

altitudealtitude ends at tropopauseends at tropopause

– Source of natural greenhouse Source of natural greenhouse effecteffect

The AtmosphereThe Atmosphere Stratosphere Stratosphere

– extends from 17km to 48kmextends from 17km to 48km– contains less matter than contains less matter than

tropospheretroposphere– ozone layer ozone layer (1000x more than (1000x more than

trop.)trop.)– very little water vapor (1000x less very little water vapor (1000x less

than trop)than trop)– very calm (good for flying), no very calm (good for flying), no

weather, suspended matter will weather, suspended matter will stay for many years, stay for many years,

Climate and WeatherClimate and Weather

What is weather?What is weather?

What is climate?What is climate?

Climate and Weather TopicsClimate and Weather Topics

Solar radiationSolar radiation Convection CurrentsConvection Currents Coriolis effectCoriolis effect Rain shadow effectRain shadow effect Jet streamsJet streams Frontal weatherFrontal weather Cyclonic stormsCyclonic storms Seasonal windsSeasonal winds ENSOENSO Milankovich cyclesMilankovich cycles

CLIMATECLIMATE

The two most important aspects of climate The two most important aspects of climate are are temperature temperature and and precipitationprecipitation..

– These two factors determine what type of These two factors determine what type of species (biome) will be found in a given location.species (biome) will be found in a given location.

The climate in an area is determined byThe climate in an area is determined by1.1. LatitudeLatitude

2.2. Direction from which winds arriveDirection from which winds arrive

3.3. Proximity to large bodies of water and mountainsProximity to large bodies of water and mountains

Solar RadiationSolar Radiation The same amount of The same amount of

sunlight hits the equator sunlight hits the equator and poles.and poles.

However, at the poles the However, at the poles the light is spread over a wider light is spread over a wider area resulting in less area resulting in less intense sunlight, and less intense sunlight, and less heating.heating.

So, the equator is warmer So, the equator is warmer than the poles.than the poles.

Convection CellsConvection Cells Warm air rises; cold air fallsWarm air rises; cold air falls Warm air holds more moisture than cold airWarm air holds more moisture than cold air When air rises, it cools; when air falls, it warmsWhen air rises, it cools; when air falls, it warms SO, warm, moist air rises, cools, and loses moisture as SO, warm, moist air rises, cools, and loses moisture as

rain; cool, dry air falls, warms, and picks up moisture from rain; cool, dry air falls, warms, and picks up moisture from the ground.the ground.

Cool, dry

warm, dryWarm, moist

precipitation

Global Convection Cells Global Convection Cells Wet areas (warm, moist air rising)Wet areas (warm, moist air rising)

– 00oo(equator) - TRF(equator) - TRF

– 6060oo (Seattle) - TempRF (Seattle) - TempRF

Dry areas (cold, dry air falling)Dry areas (cold, dry air falling)

– 3030o o - desert- desert

– 9090oo (poles) – tundra (poles) – tundra

Surface Wind CurrentsSurface Wind Currents The air traveling between these points travels The air traveling between these points travels

primarily north or south over the Earth’s surface primarily north or south over the Earth’s surface to complete the cells.to complete the cells.

This gives rise to prevailing winds that are This gives rise to prevailing winds that are predictable in all areas of the world. They have predictable in all areas of the world. They have been used by sailors for centuries. been used by sailors for centuries.

Coriolis Effect - ContCoriolis Effect - Cont As the earth spins, the air currents (which would ordinarily As the earth spins, the air currents (which would ordinarily

travel mostly north-south) are deflected by the Coriolis travel mostly north-south) are deflected by the Coriolis effect. effect. – Deflected to right in NH and left in SHDeflected to right in NH and left in SH

Coriolis videoCoriolis video This causes winds to form huge circular paths – clockwise This causes winds to form huge circular paths – clockwise

in the N. Hem and counter-clockwise in the S. Hem.in the N. Hem and counter-clockwise in the S. Hem.

Effect of Oceans and MountainsEffect of Oceans and Mountains

OceansOceans– Being near a large body of water tends to minimize Being near a large body of water tends to minimize

temperature fluctuations because of water’s high temperature fluctuations because of water’s high specific heat capacityspecific heat capacity Ex. coastal areas in CA are warmer in winter and cooler in Ex. coastal areas in CA are warmer in winter and cooler in

summer than inland areas.summer than inland areas.

Rain-shadow effectRain-shadow effect In areas where there is a strong on-shore wind pattern In areas where there is a strong on-shore wind pattern

and coastal mountains, there is a pattern of wet coastal and coastal mountains, there is a pattern of wet coastal sides and dry inland sides of the mountains.sides and dry inland sides of the mountains.

Mountains force warm, moist air upward;Mountains force warm, moist air upward; – Air cools, decreasing moisture holding capacity Air cools, decreasing moisture holding capacity – windwardwindward side is rainy side is rainy

Dry, cool air at the top of the mountain descends the to Dry, cool air at the top of the mountain descends the to other (leeward) sideother (leeward) side– the moisture-holding capacity the moisture-holding capacity as air warms as air warms – moisture is sucked from the ground, causing desertmoisture is sucked from the ground, causing desert

Longterm Effects on Climate - Longterm Effects on Climate - Milankovich CyclesMilankovich Cycles

The Earth’s tilt and orbit tend The Earth’s tilt and orbit tend to wobble over timeto wobble over time– Orbit stretches and shrinks in a Orbit stretches and shrinks in a

100,000yr cycle100,000yr cycle– Axis tilt changes in a 40,000yr Axis tilt changes in a 40,000yr

cyclecycle– Axis wobbles in a 26,000yr Axis wobbles in a 26,000yr

cyclecycle These variations impact solar These variations impact solar

radiation and result in climatic radiation and result in climatic fluctuationsfluctuations

These also limit our ability to These also limit our ability to know what is “natural” know what is “natural” variation and what is “human-variation and what is “human-induced” variation in induced” variation in temperaturestemperatures

WEATHER: Jet StreamWEATHER: Jet Stream

Giant rivers of air that Giant rivers of air that flow around the earth.flow around the earth.

Their location (north Their location (north and south) determine and south) determine which areas receive which areas receive stormsstorms

Their speed dictates Their speed dictates how fast weather how fast weather systems move across systems move across land masses.land masses.

FrontsFronts

A A frontfront is a boundary is a boundary between two air masses between two air masses of different temps (and of different temps (and pressures).pressures).– WarmWarm front – approaching front – approaching

air is warmer than local airair is warmer than local air– ColdCold front- approaching air front- approaching air

is colder than local airis colder than local air– Both can cause rain; cold Both can cause rain; cold

fronts are associated with fronts are associated with more severe weathermore severe weather

Cyclonic stormsCyclonic storms

masses of rotating air masses of rotating air caused by pressure caused by pressure differentials between differentials between the ground and air.the ground and air.

TornadoesTornadoes and form and form over land are more over land are more localizedlocalized– Form with Form with

thunderstormsthunderstorms

Typhoon/Cyclones/HurricanesTyphoon/Cyclones/Hurricanes Form in many areas Form in many areas

in the world near in the world near tropics tropics – US hurricanes mostly US hurricanes mostly

form off Africa north form off Africa north of equator.of equator.

Are fed by warm Are fed by warm waterwater

Decrease withDecrease with– Wind shearWind shear– Moving over cold Moving over cold

H2OH2O– Moving over landMoving over land

Spin CC in NH and C Spin CC in NH and C in SHin SH

Seasonal WindsSeasonal Winds

Many parts of the Many parts of the world experience world experience seasonal winds, or seasonal winds, or wind direction wind direction reversalsreversals– Ex. monsoons (rain Ex. monsoons (rain

shadow effect)shadow effect)– SiroccoSirocco– Santa AnasSanta Anas

El Nino (ENSO)El Nino (ENSO) The winds in the The winds in the

Pacific normally blow Pacific normally blow across the surface of across the surface of the water in the the water in the WestwardWestward direction direction

This causesThis causes– Rain in Indonesia, mild Rain in Indonesia, mild

winters in CA, winters in CA, upwelling off the coast upwelling off the coast of S.Am., cold surface of S.Am., cold surface waters on Eastern Pac.waters on Eastern Pac.

La Nina La Nina is an increased is an increased flow in this direction.flow in this direction.

El Nino (ENSO)El Nino (ENSO) In El Nino years, the In El Nino years, the

winds blow across the winds blow across the surface in the surface in the EasternEastern directiondirection

This causesThis causes– Drought in Indonesia, Drought in Indonesia,

wet winter in CA, (due to wet winter in CA, (due to movement of jet stream)movement of jet stream)

– no upwelling (fish and no upwelling (fish and mammal die-offs), mammal die-offs),

– warm surface water in warm surface water in Eastern Pac.Eastern Pac.