AOM 4643 Principles and Issues in Environmental Hydrology Composition/Characteristics of the Atmosphere
Agenda • A really atmospheric overview… • Spatial Distributions of temperature, pressure and precipitation – Why?
Composition/Characteristics of the Atmosphere • 80% Nitrogen, 20% Oxygen- treated as a perfect gas • Lower atmosphere extends up to 50 km. • Lower atmosphere most active part of atmosphere where most of the mass and energy transfer (leading to earth’s weather patterns) occurs. It is divided into two parts distinguished by their temperature distribution -- the troposphere and the stratosphere. • Upper atmosphere doesn’t play much of a role in the determination of weather.
Characteristics of the Atmosphere Altitude (km) Temperature C -80 -60 -40 -20 0 20 sharp change in temp. and pressure produce Jet Streams 50 km lower atmosphere Stratopause Stratosphere upper atmosphere Mesopause Mesosphere 100 km Thermosphere 8 - 16 km Tropopause Troposphere poles equator
Characteristics of the Troposphere • Variable thickness (8 km poles, 16 km equator). • Decreasing temperature with elevation (linear). • Well defined pressure gradients (max. pressure at bottom). non-linear • Well defined distribution of moisture and suspended particles (max. at bottom) •Sharp air velocity gradient. At earth’s surface velocity is zero (no-slip condition) and velocity increases over 2700 m thick boundary layer according to a logarithmic velocity profile P Elev T Elev Z o – roughness height – depends on conditions at earth’s surface Velocity Elev Z o Driving forces for energy transport in lower atmosphere
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