Chap2shengtai全球气候系统.pptx

Chapter 2 The system of global climate;Climate is the state factor that most strongly governs the global pattern of ecosystem structure and function;Climate is a key mechanism by which ecosystems interact with the total Earth System;Major goals in this lecture;;;The atmosphere is heated from the bottom Therefore it is warmest near the and gets colder with increasing elevation;Uneven heating of Earth’s surface causes atmospheric circulation Greater heating at equator than poles 1. sun’s rays hit more directly 2. less atmosphere to penetrate ;Air rises at equator and subsides at poles (vertical circulation) Circulation cells explain global distribution of rainfall Earth’s rotation determines wind direction (horizontal circulation) (Coriolis force) tropical easterlies temperate westerlies;At 30o N S, air descends more strongly over cold ocean than over land At 60 o N S, air descends over cold land (high pressure) and rises over warm ocean (low pressure) Pressure gradients create geographic variation in prevailing winds;In summer at 60 o N S, air descends over cold ocean (high pressure) and rises over warm land (low pressure) 1. Cool equator-ward flow of air on W coast of continents 2. Warm poleward flow of air on E coasts of continents Creates planetary waves ;Ocean currents are similar to wind patterns: 1. Driven by Coriolis forces 2. Driven by winds;Climate of any region is predictable from topography, wind and ocean currents Alaska’s July temperature;Warming leads to thawing of permafrost (thermokarst) in Alaska;Uneven heating of Earth’s surface causes atmospheric circulation 60% of heat transport is carried by atmosphere through storms that Move along pressure gradients 40% is carried by ocean currents (conveyor belt) surface (warm) currents move poleward deep (cold) currents move equatorward;Ocean currents move 40% of “excess heat” from equator to poles Driven by circulation of deep ocean waters Deepwater formati