大气组成和结构.pptVIP

第一章 大气概述;Atmosphere (air) is:;Earth (including its atmosphere) has a radius of about 6500 km. The atmosphere is only about 100 km thick—less than 2% of the Earth’s thickness.;Despite its relative shallowness, the atmosphere contains considerable mass: 5.14 X 10E15 kg ? that’s a mass equivalent to 5.65 billion million tons, the amount of water that would fill a lake the size of California to a depth of 13 km (7.7 miles) ;Atmospheric density decreases with altitude…;Atmospheric density decreases with altitude…;Atmospheric density decreases with altitude…;Atmospheric density decreases with altitude…;Permanent gases (constant proportion in the atmosphere) 99.999 % of atmospheric mass Nitrogen, Oxygen, Argon, Neon, Helium, Krypton(氪), Xenon(氙), Hydrogen Variable gases (small percentage, but impact the behavior of the atmosphere) Water Vapor, Carbon Dioxide, Ozone, Methane(甲烷) Homosphere(均质层) lowest 80 km - region of chemical homogeneity Heterosphere(非均质层) region above the homosphere - lighter gases (H and He); Evolution of the Atmosphere;假崔漆乎堂诱舌舷纬慌勤坚纬啊消暂秘来虑略隧狄肇砾栋脸尚骡蝗用烁磋大气组成和结构大气组成和结构; Average composition of the atmosphere up to an altitude of 25 km;Atmospheric Composition: Variable Gases;;Key Points ;Nitrogen is removed from the atmosphere and deposited at the Earths surface mainly by specialized nitrogen fixing bacteria, and by way of lightning through precipitation, supplying much needed nutrition for plant growth Oxygen is exchanged between the atmosphere and life through the processes of photosynthesis and respiration. ;Key Points (contd.);Key Points (contd.);;甲烷的增长;Key Points(contd.);This stratospheric ozone provides an important service to life on the Earth as it absorbs harmful ultraviolet radiation. In recent years, levels of stratospheric ozone have been decreasing due to the buildup of human created chlorofluorocarbons in the atmosphere. Since the late 1970s, scientists have noticed the development of severe holes in the ozone layer over Antarctica.