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Lect 22 Air and weather PP outline

Lect 22 Air and weather PP outline - Air Weather and...

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Air, Weather, and Climate The Atmosphere We live in an ocean of air that is about 1,000 miles thick. Turbulent and mobile Winds, and Weather, and Climate… Past and Present Composition Many geochemists believe the earth’s earliest atmosphere was made up of mainly hydrogen and helium. Volcanic emissions have added carbon, nitrogen, oxygen, and sulfur. Virtually all oxygen was produced by photosynthesis. Enormous changes….. Present composition of clean, dry air in the lower atmosphere Earth Atmosphere As far as we know, our atmosphere is unique in the solar system. Free oxygen and water vapor Were it different, life, as we know it, probably would not exist. Changes to the atmosphere continue to occur, at an accelerated rate…. A Layered Envelope Four distinct zones: Troposphere – closest to the surface Ranges in depth from 18 km over the equator to 8 km over the poles. All weather occurs here. Contains ~ 75-80% of the total mass of the atmosphere Composition is relatively uniform. Air temperature drops rapidly with increasing altitude. Tropopause - Transition boundary that limits mixing between the troposphere and upper zones. A Layered Envelope Stratosphere Extends from troposphere to about 50 km. Air temperature is stable, or increases with altitude. Fraction of water vapor is 1000x less and ozone is >> than in the troposphere. Ozone protects life on Earth by absorbing most (95%) of the damaging incoming solar UV radiation. Relatively calm. Little to no mixing. Ash, or human pollution, may remain for many years. A Layered Envelope Mesosphere Middle Layer.
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Minimum temperature is about - 80 o C. Thermosphere Extends to about 1,600 km. Ionized gases and high temperatures. Ionosphere - Lower Thermosphere Aurora borealis (northern lights) Energy and the Greenhouse Effect Of the solar energy that reaches the outer atmosphere: About one-quarter is reflected by clouds and the atmosphere. Another quarter is absorbed by carbon dioxide, water vapor, ozone and a few other gases. About half reaches the earth’s surface. Energy and the Greenhouse Effect Surfaces that reflect energy have a high albedo (Reflectivity).
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