Earth Systems Lecture 12

Earth Systems Lecture 12 3/3/09 Chapter 8: Climatic Zones (skip everything after page 244) Whats important? understand climate types in order to better understand the climate system the importance of physical variables, such as temperature and precipitation in shaping them association between locations and climate types the controls disregard letter codes and all kinds of numbers Climate Classification : A 2,200 year old Scheme Image on Page 212 Figure 8-1 This unrealistic scheme persisted for a long time until it was finally discarded in the 20th century. Modified KÖppen System: A more Realistic Scheme Image on Page 214 Figure 8-4 classification based on temperature and precipitation values climate zone and sub-types delineated based on vegetation types e.g. Mediterranean climate ? Csa and Csb where C = mild midlatitude climate, S = summer day, a = hot summer, b = warm summer Climographs Image on Page 216 Figure 8-5 most useful tool for classifying climate of a specific place simple graphic representation of a weather station?s monthly temperature and precipitation values ( or climatologies) Global Distribution of major Climate types six climatic zones and their subtypes Ask three questions: location characteristics controls Tropical Humid Climates (A) Image on Page 217 Figure 8-6 only true winterless climates: moderately high temperatures throughout the year. Near equatorial location; sun is high; little difference between shortest and longest days Prevalence of moisture; abundant mechanisms for uplift F = wet ; m = monsoon ; w = savanna Tropical Wet Image on page 218 Figure 8-7 Characteristics: wet all seasons generally closest to equator little wind high humidity makes for high sensible temperatures convective thunderstorms Controls: latitude Tropical Monsoon Image on Page 221 Figure 8-12 Characteristics: moderately away from equator most extensive on the windward coast of southeastern Asia wet summer dry to very dry winter spring temperature maximum Controls: latitude land and water contrast Tropical Savanna Image on Page 220 Figure 8-10 Characteristics: most extensive of the tropical climates away from equator wet summer under ITCZ very dry winter under subtropical high pressure some seasonality to temperature 3 reasons: wet, dry-cool, dry ? hot Controls: latitude Dry Climates (B) Image on Page 223 Figure 8-14 Sh, Sk ? subtropical and midlatitude steppe Wh, Wk ? subtropical and midlatitude desert 30% of the world?s land area lack of air uplift or moisture in air arid / semi ? arid; warm to hot controls: sub-tropical high continentality leeward side of mountains ocean current Subtropical highs and Subtropical deserts Image on Page 224 Figure 8-15 Subtropical desert: general subsidence enhanced on west coasts and in rain shadows precipitation is scarce and its occurrence unreliable, when it occurs it is intense large diurnal (day-night) temperature range outside of summer Subtropical steppe: surround subtropical desert a bit more precipitation, more reliable, bit cooler summer precipitation maximum equator side, winter maximum poleward side. Image on Page 226 Figure 8-16 Cool, Foggy west coast desert Image on Page 226 Figure 8-18 Midlatitude Desert and Steppe Midlatitude desert : mid continent deprived of moisture source summer precipitation maximum winter cold Midlatitude steppe: between mid latitude desert and humid Midlatitude Desert Image on Page 228 Figure 8-21 Mild Midlatitude Climates (C) Image on Page 229 Figure 8-23 may extend into subtropics and up west coasts to higher middle latitudes long ht summers; short mild winters seasonality to precipitation is common Controls: general circulation of atmosphere and ocean storms, latitude Mediterranean Climate winter precipitation (cyclonic storms) summer drought (subsidence and stability) mild winter hot summer (except near coasts) Image on Page 230 Figure 8-24 Humid Subtropical warm/hot and humid summers mild winters with sporadic cold surges considerable precipitation all year in most areas with a summer maximum (lots of thunderstorms) significant precipitation from tropical cyclones Image on Page 232 Figure 8-27 Marine West Coast lack of extreme temperatures (ocean effects) constant high humidity abundant clouds moderate precipitation (except high in mountains) frequent precipitation summers are considerably drier than winters ( because of cyclonic storms) Severe Midlatitude Climates (D) Image on Page 235 Figure 8-31 only in the Northern Hemisphere: absence of land between 40 - 70° S controls: latitude, continentality, cyclonic storms four seasons; high annual temperature range (ATR) moderate precipitation : exceeds evapotranspiration summer precipitation maximum, winter snow cover Humid Contiental warm/hot summers cold winters much day to day variation large ATR precipitation: moderate to abundant ( 20 ? 50 in) with summer maxima Image on Page 236 Figure 8-32 Subarctic brief mild summers long, dark, very cold winters enormous ATR precipitation: meager( 5- 20 in) with summer maxima; light snow in winter Image on 238 Figure 8-35 Polar Climates (E) Image on Page 239 Figure 8-36 very long, very cold winters dry but very little evaporation short cool summers Controls: Latitude Polar Anticyclones Tundra summer means temperature exceed freezing, but forget the swim suit north of tree line, but vegetation is present snow may lie on ground from September to June Image on Page 240 Figure 8-37 Ice Cap 9% of earth?s land area high altitude added to high latitude persistent temperature inversions katabatic winds very little precipitation Image on Page 242 Figure 8-38 Highland Climates (H) Image on Page 242 Figure 8-39 climate usually related to associated lowlands however some aspects differ significantly precipitation heavier in highlands than surrounding lowlands sudden changes in temperature, precipitation, storminess controls: altitude, exposure to sun and wind few hundred few hundred meters elevation = several hundred miles poleward Image on Page 244 Figure 8-40