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IntroductionClimate is the long-term statistical properties of the atmosphere for an area
Climate classifications are based on properties such as temperature, precipitation, air mass types, and water budget characteristics
The Koeppen climate classification system• Most widely used classification scheme• Based on natural vegetation types as
indicators of average weather
Tropical Climates• Warm annual temperatures and minimal
seasonal temperature variation• Differentiated on precipitation variations
Tropical Wet (Af)– Even precipitation through year– High humidity – Temperatures
– Highs = low 30°s C (80°s F) – Lows = low 20°s C (70°s F)
Monsoonal (Am)• Near tropical coastal areas • Monthly precipitation variations are
significant, with very high annual totals• Small annual temperature variations
Tropical Wet and Dry (Aw)• Poleward tropical margins• Distinct temperature and precipitation
seasonality • Low sun dry period• Unreliable precipitation
– Sahel region• Savanna vegetation
Dry Climates30% of Earth’s land surface
Defined by water balance• Potential evapotranspiration > precipitation
Subtropical Deserts (BWh)– Largest deserts
– Western sides of continents– Areas with atmospheric subsidence– High diurnal temperature ranges (low
dew points/humidity)
High precipitation variability of BWh regions
Southern California site; 1983 and 1992 were El Nino years
Subtropical Steppe (BSh)– High aridity – High precipitation and temperature
variability – Large temperature ranges– Extreme summer temperatures– Summer precipitation
Mid-Latitude Deserts (BWk)– Extreme continentality and/or rain
shadows– Asia and the Western U.S.
– Very high temperature ranges – Summer temperatures – very hot– Nighttime and winter temperatures - very
cool– Higher humidity and precipitation
Mild Mid-Latitude Climates• Eastern continental areas • Varying precipitation regimes• Mild winter temperatures • Summer temperatures may be high
Mediterranean (Csa, Csb)• Distinct summer dry period
– Subtropical high interactions• Winter precipitation is variable • Mild winter temperatures • Mild to hot summers
Humid Subtropical (Cfa, Cwa)• Eastern continental areas of the lower mid-
latitudes• High heat and moisture
– Abundant and even monthly precipitation – Weather influenced by subtropical highs
• Mild winters• Hot summers
Marine West Coast (Cfb, Cfc)• Poleward of Csb• Cold ocean current influence
– Often has fog and/or low cloud cover • Mild and even annual temperatures• High frequency of rain days
Severe Mid-latitude Climate• Very cold winters• Large continental areas• Evenly distributed annual precipitation
Humid Continental (Dfa, Dfb, Dwa, Dwb)– Eastern continents - 40o-55o N – Warm to hot summers– Cold winters– Even and abundant annual precipitation
Subarctic (Dfc, Dfd, Dwc, Dwd)– Poleward of humid continental climates – Coniferous boreal forest (taiga)– Warm, short summers – Low annual precipitation (summer
maximum)
Polar Climates• Very high latitudes • Very cold
Tundra (ET)– Tundra vegetation – Harsh winters– Mild summers of long days– Permafrost region
Ice Cap (EF)• Constant ice cover
– Greenland and Antarctica• Warmest monthly temperatures < 0oC• Katabatic winds• Low precipitation
Highland Climates (H)• Governed solely by topography• Vertical zonation
– Highly variable local climates