Part 6. Current, Past, and Future Climates Chapter 15 Earth’s Climates

Introduction Climate 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

Koeppen Classifications

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)

Af climographs Monsoonal effects seen in the precipitation trends throughout the year

Monsoonal (Am) Near tropical coastal areas Monthly precipitation variations are significant, with very high annual totals Small annual temperature variations

(strong monsoonal precipitation) Am climographs (strong monsoonal precipitation)

Tropical Wet and Dry (Aw) Poleward tropical margins Distinct temperature and precipitation seasonality Low sun dry period Unreliable precipitation Sahel region Savanna vegetation

Aw climographs

Dry Climates 30% 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)

BWh climographs

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

BSh climographs

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

BWk climographs

Mid-Latitude Steppe (BSk) A transition zone Higher annual average precipitation than true desert

BSk climographs

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

Csa, Csb climographs

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

Cfa, Cwa climographs

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

Cfb, Cfc climographs

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

Dfa, Dfb, Dwa, Dwb climographs

Subarctic (Dfc, Dfd, Dwc, Dwd) Poleward of humid continental climates Coniferous boreal forest (taiga) Warm, short summers Low annual precipitation (summer maximum)

Dfc, Dfd, Dwc, Dwd climographs

Polar Climates Very high latitudes Very cold Tundra (ET) Tundra vegetation Harsh winters Mild summers of long days Permafrost region

ET climographs

Ice Cap (EF) Constant ice cover Greenland and Antarctica Warmest monthly temperatures < 0oC Katabatic winds Low precipitation

EF climographs

Highland Climates (H) Governed solely by topography Vertical zonation Highly variable local climates

End of Chapter 15 Understanding Weather and Climate 4th Edition Edward Aguado and James E. Burt