ChapterChapter 99 TheThe GlobalGlobal ScopeScope ofof ClimateClimate ClimaticClimatic ClassificationClassification

` Latitude – Pole-to-Equator temperature gradient ` Continentality – Proximity to large bodies of water ` Seasonality – Changes in patterns during the annual cycle ClimaticClimatic ClassificationClassification

` A scheme for dividing the world into characteristic climate types

` Begun with the Ancient Greeks ƒ Frigid Zone (60°-90°N) ƒ Temperate Zone (30°-60°N) ƒ Torrid Zone ( 0°-30°N) ClimaticClimatic ClassificationClassification

` Köppen-Geiger-Pohl System ƒ Air temperature and precipitation ƒ Vegetation regimes ` Thornthwaite System ƒ Air temperature and precipitation ƒ Climatic water balance ` Terjung System ƒ Net radiation ƒ Energy balance KöppenKöppen--GeigerGeiger--PohlPohl SystemSystem TheThe ClimaticClimatic WaterWater BalanceBalance

A system of water accounting Input: Precipitation TheThe ClimaticClimatic WaterWater BalanceBalance

A system of water accounting Output: Evaporation TheThe ClimaticClimatic WaterWater BalanceBalance

A system of water accounting

` Evaporation – process by which water becomes a gas TheThe ClimaticClimatic WaterWater BalanceBalance

A system of water accounting Output: Transpiration TheThe ClimaticClimatic WaterWater BalanceBalance

A system of water accounting

` Evaporation – process by which water becomes a gas ` Transpiration – evaporative loss of water to the atmosphere through the stomata of leaves TheThe ClimaticClimatic WaterWater BalanceBalance

A system of water accounting

` Evapotranspiration – combined loss of water to the atmosphere by evaporation from the soil and transpiration from plants TheThe ClimaticClimatic WaterWater BalanceBalance A system of water accounting Output: Evapotranspiration TheThe ClimaticClimatic WaterWater BalanceBalance A system of water accounting Output: Runoff/Streamflow TheThe ClimaticClimatic WaterWater BalanceBalance A system of water accounting

PP == ETET ++ RR TheThe ClimaticClimatic WaterWater BalanceBalance

PotentialPotential EvapotranspirationEvapotranspiration Ideal rate of evapotranspiration that occurs when a complete canopy of growing plants is continuously supplied with all the soil water they need. TheThe ClimaticClimatic WaterWater BalanceBalance

PotentialPotential EvapotranspirationEvapotranspiration ` Is largely a function of air temperature ` Greatest in the tropics; Least at the poles TheThe ClimaticClimatic WaterWater BalanceBalance

PrecipitationPrecipitation MoistureMoisture SupplySupply vs.vs. PotentialPotential EvapotranspirationEvapotranspiration MoistureMoisture DemandDemand TheThe ClimaticClimatic WaterWater BalanceBalance ClassificationClassification ofof ClimateClimate

` Latitude ƒ Low-latitude Climates ( 0°-30°N) – 4 ƒ Mid-latitude Climates (30°-60°N) – 6 ƒ High-latitude Climates (60°-90°N) – 3 ` Seasonal Supply vs. Demand ƒ Seasonality ƒ Continentality ChapterChapter 1010 LowLow--LatitudeLatitude ClimatesClimates LowLow--LatitudeLatitude ClimatesClimates

` Dominated by the ƒ circulation of the Hadley Cells LowLow--LatitudeLatitude ClimatesClimates

` Dominated by the ƒ circulation of the Hadley Cells ƒ seasonal migration of the ITCZ

LowLow--LatitudeLatitude ClimatesClimates

` Dominated by the ƒ circulation of the Hadley Cells ƒ seasonal migration of the ITCZ ƒ prevailing easterly trade winds LowLow--LatitudeLatitude ClimatesClimates

` Dominated by the ƒ circulation of the Hadley Cells ƒ seasonal migration of the ITCZ ƒ prevailing easterly trade winds ` Characterized by a relatively uniform air temperature regime all year long ƒ Consequently, potential evapotranspiration is nearly constant all year long Potential Evapotranspiration – Low-Latitudes 1)1) WetWet EquatorialEquatorial ClimateClimate

` Associated with the ITCZ all year long ` mE air mass dominates, some mT ` Rainfall is plentiful during the entire year ƒ Annual total exceeds 250 cm ` Air temperature is relatively uniform ƒ Mean air temperature near 27°C WetWet EquatorialEquatorial ClimateClimate WetWet EquatorialEquatorial ClimateClimate Iquitos, Peru – 3°S 2)2) DryDry TropicalTropical ClimateClimate

` Descending air of the Hadley Cell ` Sub-tropical High Pressure dominates ` Little rainfall during the entire year ƒ Desert environment ` Air temperature has a slight seasonal trend ƒ Greatest air temperatures during the high-sun season DryDry TropicalTropical ClimateClimate DryDry TropicalTropical ClimateClimate Wadi Halfa, Sudan -- 22°N 3)3) TropicalTropical WetWet && DryDry ClimateClimate

` Seasonal migration of the ITCZ ` Sub-tropical High Pressure in low-sun season; mE in high-sun season ` Marked seasonal cycle to precipitation ƒ Precipitation “follows the sun” ` Air temperature has a slight seasonal trend ƒ Greatest air temperatures during the high-sun season TropicalTropical WetWet && DryDry ClimateClimate (N.H.)(N.H.) TropicalTropical WetWet && DryDry ClimateClimate (S.H.)(S.H.) TropicalTropical WetWet && DryDry ClimateClimate Timbo, Guinea -- 10°N TropicalTropical WetWet && DryDry ClimateClimate 4)4) TradeTrade--WindWind CoastalCoastal ClimateClimate

` East coasts – windward side of the continent ` Monsoon climate – wind shift during year ` Marked seasonal cycle to precipitation ƒ Precipitation “follows the sun” ` Air temperature has a slight seasonal trend ƒ Greatest air temperatures during the high-sun season TradeTrade--WindWind CoastalCoastal ClimateClimate (N.H.)(N.H.) TradeTrade--WindWind CoastalCoastal ClimateClimate (S.H.)(S.H.) TradeTrade--WindWind CoastalCoastal ClimateClimate Belize City, Belize, Sudan -- 17°N TradeTrade--WindWind CoastalCoastal ClimateClimate Cochin, India -- 10°N LowLow--LatitudeLatitude ClimatesClimates ChapterChapter 1111 MidMid--LatitudeLatitude andand HighHigh--LatitudeLatitude ClimatesClimates TheThe ClimaticClimatic WaterWater BalanceBalance ClassificationClassification ofof ClimateClimate

` Latitude ƒ Low-latitude Climates ( 0°-30°N) – 4 ƒ Mid-latitude Climates (30°-60°N) – 6 ƒ High-latitude Climates (60°-90°N) – 3 ` Seasonal Supply vs. Demand ƒ Seasonality ƒ Continentality MidMid--LatitudeLatitude ClimatesClimates MidMid--LatitudeLatitude ClimatesClimates

` Dominated by the prevailing westerlies ƒ Primarily Northern Hemisphere climates ƒ West-to-east movement of cyclones and fronts ` Latitude is a secondary factor ` Consists of six climate types ƒ Three in the lower mid-latitudes – subtropics ƒ Three in the upper mid-latitudes MidMid--LatitudeLatitude ClimatesClimates Potential Evapotranspiration – Subtropics 1)1) DryDry SubtropicalSubtropical ClimateClimate

` Extension of the Dry Tropical climate into mid- latitudes ` Source region for cT air masses ` Distinct cool season occurs during winter ` Low precipitation all year long DryDry SubtropicalSubtropical ClimateClimate DryDry SubtropicalSubtropical ClimateClimate DryDry SubtropicalSubtropical ClimateClimate Yuma, Arizona – 33°N 2)2) MoistMoist SubtropicalSubtropical ClimateClimate

` Flow of air from mT from the western edge of the subtropical High pressure ` Strong annual air temperature cycle with no winter month averaging below freezing ` Abundant rainfall all year long; cyclonic in winter, convectional in summer ` High humidity ` “Hurricane Coast” MoistMoist SubtropicalSubtropical ClimateClimate MoistMoist SubtropicalSubtropical ClimateClimate MoistMoist SubtropicalSubtropical ClimateClimate MoistMoist SubtropicalSubtropical ClimateClimate, Charleston, South Carolina – 33°N MoistMoist SubtropicalSubtropical ClimateClimate EffectEffect ofof thethe SubtropicalSubtropical HighHigh 3)3) MediterraneanMediterranean ClimateClimate MediterraneanMediterranean ClimateClimate

` Dominated by the influence of cT air in summer, mT air in winter ` Strong High pressure offshore in summer deflects storm tracks to the north ` Moderate temperature range with warm to hot summers and mild winters ` Wet winter and dry summer Æ Seasonal MediterraneanMediterranean ClimateClimate MediterraneanMediterranean ClimateClimate Monterey, Californa – 36°N MediterraneanMediterranean ClimateClimate SubtropicalSubtropical ClimatesClimates Potential Evapotranspiration – Upper Mid-latitudes UpperUpper MidMid--LatitudeLatitude ClimatesClimates 4)4) MarineMarine WestWest CoastCoast ClimateClimate

` Dominated by mP air masses and onshore flow of moist air from the westerlies ` Temperature cycle moderated by marine influence of warm, offshore ocean current – cool summers, mild winters ` Abundant precipitation, often with a winter maximum and usually accentuated by orographic effects MarineMarine WestWest CoastCoast ClimateClimate MarineMarine WestWest CoastCoast ClimateClimate MarineMarine WestWest CoastCoast ClimateClimate, Vancouver, British Columbia – 49°N UpperUpper MidMid--LatitudeLatitude ClimatesClimates 5)5) DryDry MidlatitudeMidlatitude ClimateClimate

` Dominated by dry cP air masses ` Strong air temperature cycle with large annual range – summers are warm to hot, winters are cold and snowy ` Little precipitation due to the rainshadow effect and interior continental location – slight summer maximum DryDry MidlatitudeMidlatitude ClimateClimate DryDry MidlatitudeMidlatitude ClimateClimate DryDry MidlatitudeMidlatitude ClimateClimate, Pueblo, Colorado – 38°N UpperUpper MidMid--LatitudeLatitude ClimatesClimates 6)6) MoistMoist ContinentalContinental ClimateClimate

` Dominated by frontal interactions between dry cP and moist mT air masses ` Summers warm, winters cold; relatively large annual air temperature range ` Ample precipitation with a slight summer maximum – convective in summer; cyclonic in winter MoistMoist ContinentalContinental ClimateClimate MoistMoist ContinentalContinental ClimateClimate MoistMoist ContinentalContinental ClimateClimate, Madison, Wisconsin – 43°N MoistMoist ContinentalContinental ClimateClimate UpperUpper MidlatitudeMidlatitude ClimatesClimates MoistMoist ContinentalContinental ClimateClimate MidlatitudeMidlatitude ClimatesClimates HighHigh--LatitudeLatitude ClimatesClimates HighHigh--LatitudeLatitude ClimatesClimates

` Dominated by the Arctic Air Mass ƒ Primarily Northern Hemisphere climates ƒ One, however, is present in the Southern Hemisphere – in Antarctica (dominated by the Antarctic Air Mass) HighHigh--LatitudeLatitude ClimatesClimates

` Dominated by the Arctic Air Mass ƒ Primarily Northern Hemisphere climates ƒ Also found along the tip of Antarctica near Chile (dominated by Antarctic Air Mass) ` Consists of only three climateclimate types,types, stratified primarily by latitude and proximity to the coast Potential Evapotranspiration – High-Latitudes 1)1) ContinentalContinental SubarcticSubarctic ClimateClimate

` Associated with Boreal Forest vegetation ` Short, cool summer – long, very cold winter ` Greatest Annual Air Temperature Range ` Source region for cP air masses – located mainly in the continental interiors ` Little rainfall, falling mostly in the summer ContinentalContinental SubarcticSubarctic ClimateClimate ContinentalContinental SubarcticSubarctic ClimateClimate Fort Vermillion, Alberta – 57°N ContinentalContinental SubarcticSubarctic ClimateClimate ContinentalContinental SubarcticSubarctic ClimateClimate Yatkutsk, Russia – 61°N 2)2) TundraTundra ClimateClimate

` Coastal Arctic fringe climate ` Maritime influence keeps winter warmer than Continental Subarctic ` Very short summer, very long winter ` Low annual precipitation total TundraTundra ClimateClimate TundraTundra ClimateClimate Upernivik, Greenland – 73°N TundraTundra ClimateClimate TundraTundra ClimateClimate Barrow Point, Alaska – 71°N 3)3) IceIce SheetSheet ClimateClimate

` Source region for cA and cAA air masses ` All months are below freezing – no growth ` Lowest Global Air Temperatures ` Polar deserts – very low precipitation totals although snow accumulates IceIce SheetSheet ClimateClimate IceIce SheetSheet ClimateClimate IceIce SheetSheet ClimateClimate HighHigh LatitudeLatitude ClimatesClimates ClimateClimate andand OceanOcean CurrentsCurrents Hypothetical Northern Hemisphere Continent ClimateClimate andand SurfaceSurface WindsWinds Hypothetical Northern Hemisphere Continent Climate,Climate, OceanOcean Currents,Currents, andand SurfaceSurface WindsWinds Hypothetical Northern Hemisphere Continent