Chapter 4.1 What Causes Climate?. Climate vs. Weather Weather is the condition of the atmosphere at a particular time and place Climate is the average,

Chapter 4 .1Chapter 4 .1

What Causes Climate?What Causes Climate?

Climate vs. WeatherClimate vs. Weather

WeatherWeather is the condition of the is the condition of the atmosphere at a particular time and atmosphere at a particular time and

placeplace

ClimateClimate 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

What factors determine the climate What factors determine the climate of a region?of a region?

Two factors determine climate:Two factors determine climate:

Temperature Temperature

PrecipitationPrecipitation

Climate regionClimate region – is a large area with – is a large area with similar climate conditions throughoutsimilar climate conditions throughout

Factors affecting TemperatureFactors affecting Temperature

LatitudeLatitude Farther from the equator, the cooler Farther from the equator, the cooler

the climatethe climate Tropical zoneTropical zone 23.5 degrees North 23.5 degrees North

and South of the equatorand South of the equator Temperate zoneTemperate zone 23.5-66.5 degrees 23.5-66.5 degrees

North and South of the equatorNorth and South of the equator Polar zonePolar zone: 66.5-90 degrees: 66.5-90 degrees

Factors affecting temperatureFactors affecting temperatureAltitude:Altitude:

high mountains will high mountains will have cool climates have cool climates independent of independent of where the latitude where the latitude is is – ex. Mt Kilimanjaro ex. Mt Kilimanjaro

in Africa has snow in Africa has snow on its top even on its top even though it is 3 though it is 3 degrees from the degrees from the equator.equator.

Factors affecting TemperatureFactors affecting Temperature Distance from large bodies of waterDistance from large bodies of water

Coastal areas have a Coastal areas have a marine climatemarine climate (water heats up more slowly than land; it (water heats up more slowly than land; it also cools down more slowly) warm also cools down more slowly) warm winters, cool summerswinters, cool summers

Because of winds from the ocean, Because of winds from the ocean, temperature extremes are not common.temperature extremes are not common.

Factors affecting TemperatureFactors affecting Temperature

Continental climates - areas too far Continental climates - areas too far inland to be warmed or cooled by the inland to be warmed or cooled by the oceans. oceans.

Interior areas of the US, Canada, Interior areas of the US, Canada, Russia Russia

have a more extreme climate, hot have a more extreme climate, hot summers, bitterly cold winterssummers, bitterly cold winters

Factors affecting temperatureFactors affecting temperature Ocean Currents – Ocean Currents – streams of water streams of water

within the oceans that move in within the oceans that move in regular patterns.regular patterns.

““Warm” water currents originate from the Warm” water currents originate from the Equatorial regions and move North or Equatorial regions and move North or South South – ex. ex. Gulf Stream ( best known water current)Gulf Stream ( best known water current)

““Cold’ water current originate in the Polar Cold’ water current originate in the Polar regions and move south making climates regions and move south making climates cooler cooler – ex. ex. CaliforniaCalifornia currentcurrent

Factors affecting PrecipitationFactors affecting Precipitation

Prevailing WindsPrevailing Winds Air masses are moved by the Air masses are moved by the

prevailing winds. Air masses may be prevailing winds. Air masses may be hot or cool, wet or dry.hot or cool, wet or dry.– Ex. Air masses near the equator are hot Ex. Air masses near the equator are hot

and humid, produce lots of rainfall and and humid, produce lots of rainfall and have thick vegetationhave thick vegetation

– Ex. Winds blowing Ex. Winds blowing over landover land (trade (trade winds in Africa), carry little moisture and winds in Africa), carry little moisture and produce desertsproduce deserts

Factors affecting PrecipitationFactors affecting Precipitation

Mountain RangesMountain Ranges The presence of a mountain range will The presence of a mountain range will

act to force air to move up the act to force air to move up the mountain side,mountain side,

On the On the windwardwindward side the air is side the air is cooled and drops its moisture as rain cooled and drops its moisture as rain or snowor snow

on the on the leewardleeward side the air is dryer side the air is dryer producing desert like environments.producing desert like environments.

MicroclimatesMicroclimates

Sometimes a small area (ex wooded Sometimes a small area (ex wooded park)park)

has a climate all its own because has a climate all its own because the moisture from transpiration from the moisture from transpiration from trees in the park keeps it cooler and trees in the park keeps it cooler and more humid than the surrounding more humid than the surrounding city environment. city environment.

This is called a This is called a microclimatemicroclimate

The SeasonsThe Seasons

Affected by the tilt of the earth’s axis Affected by the tilt of the earth’s axis (23.5)(23.5)

Winter and summer are determined Winter and summer are determined by the tilt towards (summer) or away by the tilt towards (summer) or away (winter) of each hemisphere(winter) of each hemisphere