The Physical EnvironmentThe Physical Environment

ClimateClimate

Climate vs. WeatherClimate vs. Weather

Climate—long-term average pattern of weatherClimate—long-term average pattern of weather--local, regional, or global--local, regional, or global

Weather—the combination of factors Weather—the combination of factors --temperature--temperature--humidity--humidity--precipitation --precipitation --wind--wind--cloudiness--cloudiness--atmospheric conditions--atmospheric conditions

The greatest constraintThe greatest constraint

Availability of heat and waterAvailability of heat and water Influences amount of solar energy that Influences amount of solar energy that

plants can captureplants can capture Controls distribution and abundance of Controls distribution and abundance of

plants and animalsplants and animals

I. Solar radiationI. Solar radiation

A. The earth is covered with solar A. The earth is covered with solar radiation as radiation as photonsphotons..

--51% reaches surface of earth--51% reaches surface of earth

--most of this % is converted back to--most of this % is converted back to heat warming the atmosphere heat warming the atmosphere

--small % used in photosynthesis--small % used in photosynthesis

--this radiation causes thermal patterns--this radiation causes thermal patterns

B. Thermal patterns + earth’s rotation + B. Thermal patterns + earth’s rotation + movement around sun =movement around sun =

prevailing winds and ocean currentsprevailing winds and ocean currents

These winds and ocean currents These winds and ocean currents influence distribution of rainfall.influence distribution of rainfall.

II. Greenhouse effectII. Greenhouse effect

A.A. Intercepted solar radiation varies with Intercepted solar radiation varies with latitude—2 influencing factorslatitude—2 influencing factors

• The radiation hits earth’s surface at a The radiation hits earth’s surface at a greater angle, spreading greater angle, spreading over a larger areaover a larger area

• Also traveling through Also traveling through more atmosphere, more atmosphere, or a deeper layer of airor a deeper layer of air

B.B. Tilt of earth is 23.5Tilt of earth is 23.5oo with respect to sun with respect to sun

——results in seasonal variation in results in seasonal variation in temperature and length of day temperature and length of day

1. Spring (1. Spring (vernalvernal) equinox) equinox

2. Fall (2. Fall (autumnalautumnal) equinox) equinox

3. 3. Summer solsticeSummer solstice—June 22—June 22ndnd

4. 4. Winter solsticeWinter solstice—December 22—December 22ndnd

III. Seasonality of solar III. Seasonality of solar radiationradiation

Temperature variation /day length Temperature variation /day length increases with latitudeincreases with latitude

Arctic and Antarctic –day length varies Arctic and Antarctic –day length varies from 0-24 hoursfrom 0-24 hours

Variations in Variations in solar radiationsolar radiation

Explain latitudinal changesExplain latitudinal changes Seasonal changesSeasonal changes Daily changes in temperatureDaily changes in temperature

BUT, do BUT, do notnot explain explain why temperature getswhy temperature getscolder with altitude…colder with altitude…

BUT, do BUT, do notnot explain explain why temperature getswhy temperature getscolder with altitude…colder with altitude…

As air reaches a higher altitude it As air reaches a higher altitude it becomes less dense—becomes less dense—Adiabatic coolingAdiabatic cooling—results from the —results from the fewer collisions of the air moleculesfewer collisions of the air molecules

--the rate of temperature change with --the rate of temperature change with elevation is called elevation is called adiabatic lapse rateadiabatic lapse rate

IV. Circulation of air massesIV. Circulation of air masses

Air masses circulate globallyAir masses circulate globally Warmest air at equatorWarmest air at equator Moves north and south toward polesMoves north and south toward poles Cools, becomes heavierCools, becomes heavier Sinks over Arctic/Antarctic Sinks over Arctic/Antarctic

regions regions Then flows toward equatorThen flows toward equator

—replacing warm air—replacing warm air

V. Rotation of earthV. Rotation of earth

East-west rotation of earthEast-west rotation of earth– Deflects pattern of airDeflects pattern of air– Causes Causes Coriolis force/effectCoriolis force/effect– Causes right deflectionCauses right deflection

in N. hemisphere in N. hemisphere» Including air massesIncluding air masses

– Causes left deflectionCauses left deflection in S. hemisphere in S. hemisphere » Including air massesIncluding air masses

Wind flowsWind flowsPrevailing winds formed by Coriolis forcePrevailing winds formed by Coriolis force

Series of belts of prevailing windsSeries of belts of prevailing windsPolar regions—Polar regions—Polar easterliesPolar easterlies

Equator region—Equator region—Easterly trade windsEasterly trade windsMiddle latitudes—Middle latitudes—WesterliesWesterlies

DoldrumsDoldrums——low pressure around low pressure around equatorequator

Wind patternsWind patterns

Initiate surface flow in oceansInitiate surface flow in oceans Each ocean dominated by 2 great Each ocean dominated by 2 great

circular water motions—circular water motions—gyresgyres– Northern hemisphere—Northern hemisphere—

clockwise currentsclockwise currents– Southern Southern

hemisphere—hemisphere—counterclockwise counterclockwise currentcurrent

VI. Temperature/moistureVI. Temperature/moisture

1.1. Influences amount of moisture air can holdInfluences amount of moisture air can hold» Warm air holds more moisture than cold airWarm air holds more moisture than cold air

2.2. Amount of water vapor held in a volume Amount of water vapor held in a volume of air = of air = saturation vapor pressuresaturation vapor pressure

3.3. Amount of water expressed as percentage of Amount of water expressed as percentage of saturation vapor pressure = saturation vapor pressure = relative humidity relative humidity

4.4. Temperature which saturation vapor pressure Temperature which saturation vapor pressure is is dew point temperaturedew point temperature

VII. Global patterns VII. Global patterns

Precipitation exhibits a global patternPrecipitation exhibits a global pattern Temperature, wind and ocean currents Temperature, wind and ocean currents

determine global pattern of precipitationdetermine global pattern of precipitation Westerly winds move across tropical Westerly winds move across tropical

oceans—gather moistureoceans—gather moisture Warm air cools as it rises—dew point Warm air cools as it rises—dew point

reachedreached Clouds form—precipitation fallsClouds form—precipitation falls

Annual world precipitationAnnual world precipitation

VII. Global patterns con’tVII. Global patterns con’t

Winds move northward and southwardWinds move northward and southward—cooling—cooling

Cool air descendsCool air descends 2 belts of dry climate encircle the world2 belts of dry climate encircle the world Descending air warms/holds more Descending air warms/holds more

moisturemoisture Draws water from Draws water from

the surface of earththe surface of earth

VIII. MicroclimatesVIII. Microclimates

A. Small areas where environmental A. Small areas where environmental conditions are different conditions are different– Organisms find their niche in Organisms find their niche in microclimatesmicroclimates– Vegetation can reduce ground temperature Vegetation can reduce ground temperature

7-127-12ooCC– Heavy grass cover can Heavy grass cover can

reduce wind at groundreduce wind at groundlevellevel

B.B. Common microclimatesCommon microclimates

North facing slopesNorth facing slopesExhibit one type of microclimateExhibit one type of microclimate

South facing slopesSouth facing slopesExhibit another microclimateExhibit another microclimate

C. Mountainous topographyC. Mountainous topography

1.1. Influences local/regional microclimatesInfluences local/regional microclimates» Changes patterns of precipitationChanges patterns of precipitation

2.2. Intercepts air flowIntercepts air flow3.3. Air mass reaches mountains-ascends-Air mass reaches mountains-ascends-

cools-becomes saturatedcools-becomes saturated4.4. Releases moisture Releases moisture

on windward sideon windward side5.5. Cool, dry air descends Cool, dry air descends

other side—picks up other side—picks up moisture from landmoisture from land

Phenomenon is called Phenomenon is called rain shadowrain shadow Found at continental divideFound at continental divide Found on Hawaiian IslandsFound on Hawaiian Islands