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 Frigid Zone (60°-90°N) Temperate Zone (30°-60°N) Torrid Zone ( 0°-30°N) ClimaticClimatic ClassificationClassification ` Köppen-Geiger-Pohl System Air temperature and precipitation Vegetation regimes ` Thornthwaite System Air temperature and precipitation Climatic water balance ` Terjung System Net radiation 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 Low-latitude Climates ( 0°-30°N) – 4 Mid-latitude Climates (30°-60°N) – 6 High-latitude Climates (60°-90°N) – 3 ` Seasonal Supply vs. Demand Seasonality Continentality ChapterChapter 1010 LowLow--LatitudeLatitude ClimatesClimates LowLow--LatitudeLatitude ClimatesClimates ` Dominated by the circulation of the Hadley Cells LowLow--LatitudeLatitude ClimatesClimates ` Dominated by the circulation of the Hadley Cells seasonal migration of the ITCZ LowLow--LatitudeLatitude ClimatesClimates ` Dominated by the circulation of the Hadley Cells seasonal migration of the ITCZ prevailing easterly trade winds LowLow--LatitudeLatitude ClimatesClimates ` Dominated by the circulation of the Hadley Cells seasonal migration of the ITCZ prevailing easterly trade winds ` Characterized by a relatively uniform air temperature regime all year long 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 Annual total exceeds 250 cm ` Air temperature is relatively uniform 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 Desert environment ` Air temperature has a slight seasonal trend 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 Precipitation “follows the sun” ` Air temperature has a slight seasonal trend 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 Precipitation “follows the sun” ` Air temperature has a slight seasonal trend 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 Low-latitude Climates ( 0°-30°N) – 4 Mid-latitude Climates (30°-60°N) – 6 High-latitude Climates (60°-90°N) – 3 ` Seasonal Supply vs. Demand Seasonality Continentality MidMid--LatitudeLatitude ClimatesClimates MidMid--LatitudeLatitude ClimatesClimates ` Dominated by the prevailing westerlies Primarily Northern Hemisphere climates West-to-east movement of cyclones and fronts ` Latitude is a secondary factor ` Consists of six climate types Three in the lower mid-latitudes – subtropics 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