Chapter 13Chapter 13

Section 1: Atmosphere and Section 1: Atmosphere and Climate ChangeClimate Change

TermsTerms

Weather: state of the atmosphere at a Weather: state of the atmosphere at a particular place at a particular moment.particular place at a particular moment.

Climate: long-term prevailing weather Climate: long-term prevailing weather conditions at a particular place based conditions at a particular place based upon records taken.upon records taken.

What Factors Determine Climate?What Factors Determine Climate?

LatitudeLatitude Atmospheric circulation Atmospheric circulation

patternspatterns Oceanic Circulation Oceanic Circulation

patternspatterns Local geography of an Local geography of an

areaarea Solar activitySolar activity Volcanic ActivityVolcanic Activity Distance from the equatorDistance from the equator

LatitudeLatitude

Distance from the Distance from the equator measured in equator measured in degrees north or degrees north or south of the equator.south of the equator.

Low latitudes: Low latitudes: temperatures high temperatures high year-round. No year-round. No summers or winters.summers or winters.

High latitudes: yearly High latitudes: yearly temperature range is temperature range is larger.larger.

Atmospheric CirculationAtmospheric Circulation

Cold air sinksCold air sinks As cold air sinks, it As cold air sinks, it

compresses and compresses and warms.warms.

Warm air rises, Warm air rises, expands and cools.expands and cools.

Solar energy heats the ground, which Solar energy heats the ground, which warms the air above it.warms the air above it.

This warm air rises, and cooler air moves This warm air rises, and cooler air moves in to replace it. (WIND)in to replace it. (WIND)

Circulation pattern determines Circulation pattern determines precipitation pattern.precipitation pattern.Areas near equator are warmer, warm air Areas near equator are warmer, warm air

holds more water. As water cools, it cannot holds more water. As water cools, it cannot hold as much water—this leads to rain.hold as much water—this leads to rain.

Global Circulation PatternsGlobal Circulation Patterns

Cool air over the equator is forced toward the Cool air over the equator is forced toward the poles.poles.

Cold, dry air descends at the poles, which are Cold, dry air descends at the poles, which are essentially very cold deserts.essentially very cold deserts.

Coriolis Effect – air defected from its path due to Coriolis Effect – air defected from its path due to earth’s rotationearth’s rotation

http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/fw/gifs/coriolis.movhttp://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/fw/gifs/coriolis.mov

Three Prevailing WindsThree Prevailing WindsDue to Coriolis Due to Coriolis

EffectEffect

Polar Polar easterlieseasterlies

WesterliesWesterliesTrade WindsTrade Winds

Prevailing WindsPrevailing Winds

Prevailing windsPrevailing winds: winds that blow : winds that blow predominantly in one direction throughout predominantly in one direction throughout the year.the year.Trade winds: Blow from the northeast in the Trade winds: Blow from the northeast in the

Northern hemisphere and the southeast in the Northern hemisphere and the southeast in the Southern hemisphere. Near the equator.Southern hemisphere. Near the equator.

Westerly's: northwest winds in Northern Westerly's: northwest winds in Northern hemisphere, and southwest winds in the hemisphere, and southwest winds in the Southern hemisphere. 30-60Southern hemisphere. 30-60oo latitude latitude

Easterlies: cold dry air – cold desertsEasterlies: cold dry air – cold deserts

Oceanic Circulation PatternsOceanic Circulation Patterns

Surface currents affect the Surface currents affect the climate in many parts of the climate in many parts of the world.world.El NiEl Niňňo: Pacific ocean is o: Pacific ocean is

warmer than usual. Causes warmer than usual. Causes increased rainfall in some areas increased rainfall in some areas and droughts in others.and droughts in others.

La NiLa Niňňa: (opposite) Pacific is a: (opposite) Pacific is cooler than usual. cooler than usual.

TopographyTopography

Mountains trap clouds, which can cause Mountains trap clouds, which can cause rain on one side and dry air and climate on rain on one side and dry air and climate on the other.the other.

Other Influences on Earth’s ClimateOther Influences on Earth’s Climate

Sun: Increased UV Sun: Increased UV rays = increased rays = increased ozone = warmer ozone = warmer atmosphere.atmosphere.

Volcanic eruptions: Volcanic eruptions: sulfur dioxide sulfur dioxide released reflects released reflects sunlight and causes sunlight and causes global temp. to global temp. to decrease.decrease.

Seasonal Changes in ClimateSeasonal Changes in Climate

Seasons change as a Seasons change as a result of the earth’s tilt result of the earth’s tilt on its axis.on its axis.

Northern hemisphere Northern hemisphere tilts toward sun in tilts toward sun in summer and away from summer and away from it during winter.it during winter.