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Chapter 18: Chapter 18: Climate and Climate Climate and Climate ChangeChange, 18-1: What Causes , 18-1: What Causes

Climate?Climate? ““Weather” is the condition of the Weather” is the condition of the

atmosphere at a certain place and timeatmosphere at a certain place and time Climate Climate is the average year-after-is the average year-after-

year conditions of temperature, year conditions of temperature, precipitation, winds, and clouds in an precipitation, winds, and clouds in an areaarea

Two main factors determine the Two main factors determine the climateclimate of a region: of a region: temperature temperature and and precipitationprecipitation

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18-1 Factors affecting temperature18-1 Factors affecting temperature

The main factors that influence The main factors that influence temperature are latitude, altitude, temperature are latitude, altitude, distance from large bodies of water, distance from large bodies of water, and ocean currents.and ocean currents.

LatitudeLatitude is the distance from the equator, is the distance from the equator, measured in degrees.measured in degrees.

Climates of areas farther from the equator Climates of areas farther from the equator tend to be cooler than areas close to the tend to be cooler than areas close to the equator.equator.

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18-1 Factors affecting temperature: Latitude 18-1 Factors affecting temperature: Latitude Earth’s temperature zones based on latitudeEarth’s temperature zones based on latitude

• Tropical zone: Near the equator, between 23.5° North and 23.5° South, climates are warm. Frequent direct sunlight

• Temperate zones: Between tropical and polar zones (23.5°-66.5°North, and also 23.5°-66.5°South). Climates in these areas vary from having warm or hot summers to having cool or cold winters

• Polar zones: Near poles, from 66.5° to 90° North and from 66.5° to 90° South, climates are cold

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Climate ZonesClimate Zones

http://www.cgrove417.org/fry/Science/Climate/climate%20graphics/Climatezones.jpg

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Climate ZonesClimate Zones

http://www.iteachbio.com/Life%20Science/Ecology/ClimateZones.png

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18-1Factors affecting temperature18-1Factors affecting temperatureAltitudeAltitude

• The temperature of the troposphere decreases about 6.5° Celsius for every 1-kilometer increase in altitude.

*Highland areas everywhere have cool climates

* Mount Kilimanjaro is 39° Celsius cooler at it’s peak than the air at sea level at the same latitude

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Mount KilamanjaroMount Kilamanjaro

http://www.destination360.com/africa/tanzania/images/s/mount-kilimanjaro.jpg

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18-1 Factors affecting 18-1 Factors affecting temperature: temperature: Distance from large bodies of Distance from large bodies of waterwater• Oceans or large lakes can affect Oceans or large lakes can affect

temperaturestemperatures• Oceans/large lakes moderate (make less Oceans/large lakes moderate (make less

extreme) temperatures of nearby landextreme) temperatures of nearby land• Water heats up more slowly and cools Water heats up more slowly and cools

down more slowly than landdown more slowly than land• Winds from the ocean keep coastal areas Winds from the ocean keep coastal areas

from reaching extreme temperaturesfrom reaching extreme temperatures• Marine climatesMarine climates have warm winters and have warm winters and

cool summerscool summers

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18-1 Factors affecting 18-1 Factors affecting temperature:temperature:Ocean currentsOcean currents• Mary marine climates are influenced Mary marine climates are influenced

by ocean currentsby ocean currents• Generally, warm currents from Generally, warm currents from

tropics carry warm water toward tropics carry warm water toward poles while cold currents from poles poles while cold currents from poles carry cold water towards the equatorcarry cold water towards the equator

• The air over these currents is The air over these currents is warmed or cooled and affects the warmed or cooled and affects the land nearbyland nearby

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Gulf Stream & Gulf Stream & EuropeEurope

http://www.johnchaple.co.uk/images/le-gulf-stream.jpg

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Global Average Global Average TemperaturesTemperatures

http://www.climate-charts.com/images/world-temperature-map.png

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18-1 Factors affecting Precipitation18-1 Factors affecting Precipitation

• The main factors that affect precipitation are prevailing winds and the presence of mountains.

• Air masses are moved by prevailing winds. The characteristics of the air in an air mass will determine how much rain or snow can fall.

• Prevailing westerlies air masses across the United States.

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18-1 Factors affecting precipitation:18-1 Factors affecting precipitation:Mountain RangesMountain Ranges

• A mountain range in the path of prevailing winds can influence where precipitation falls

* When humid winds blow from the ocean toward a mountain range the air is forced to rise up to pass the mountains. The warm humid air cools and condenses this forms clouds and maybe rain or snow

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Eisenhower Tunnel in ColoradoEisenhower Tunnel in Colorado

http://images.travelpod.com/users/chmk11/1.1263678962.i---70-entering-eisenhower-tunnel.jpg

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Eisenhower Tunnel in ColoradoEisenhower Tunnel in Colorado

http://images.travelpod.com/users/chmk11/1.1263678962.the-easy-route-is-boring.jpg

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Sierra Nevada MountainsSierra Nevada Mountains

http://www.atmos.umd.edu/~dankd/MesDes3/images/SierraNevada5.jpg

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18-1 Factors affecting precipitation:18-1 Factors affecting precipitation:Mountain RangesMountain Ranges

• Rain or snow tends to fall on the windward side of the mountain, the side that oncoming wind hits

• The leeward side of the mountain which is downwind from the windward side is in a “rain shadow”. The air on the leeward side tends to be drier than the windward side where the rain or snow falls, after being removed from the humid wind

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18-1 Microclimates18-1 Microclimates

A A microclimate microclimate is a small area with is a small area with specific climate conditions that may be specific climate conditions that may be different from the surrounding areadifferent from the surrounding area

Inland mountains, lakes, forests, and Inland mountains, lakes, forests, and other natural features can influence the other natural features can influence the climate nearby, resulting in a climate nearby, resulting in a microclimatemicroclimate

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Global AverageTemperaturesGlobal AverageTemperatures

http://www.climate-charts.com/images/world-temperature-map.png

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18-1 Seasons18-1 Seasons

Most places on Earth outside of the Most places on Earth outside of the tropics have four seasons: winter, spring, tropics have four seasons: winter, spring, summer and autumnsummer and autumn

The seasons are caused by the tilt of The seasons are caused by the tilt of Earth’s axis as Earth travels around Earth’s axis as Earth travels around the sun.the sun. Earth is tilted at an angle of Earth is tilted at an angle of 23.523.5° on its axis.° on its axis.