Meteorology for Air Pollution Control Engineers27

Meteorology for Air Pollution Control Engineers27 - 3 n...

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1 n Wind speed increases with elevation, most of the time, in  most of the troposphere. The reason is that ground  friction slows the wind. n Typically the wind will reach its frictionless velocity  (called the geostrophic or gradient velocity) at about 500  m above the ground.
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2 n The region below this elevation, where ground friction plays a  significant role, is the planetary boundary layer. n When the atmosphere is stable or has an inversion, there is little  vertical movement; and the coupling between the planetary  boundary layer and the geostrophic wind is weak. n Thus, inversions and stable atmospheres are normally associated  with low ground-level wind velocities.
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Unformatted text preview: 3 n When the planetary boundary layer is unstable there is a great deal of vertical motion in the lower atmosphere and thus a great deal of momentum transfer between the planetary boundary layer and the geostrophic wind. n Thus unstable atmospheres have higher ground-level wind velocities than stable ones. 4 n The increase in ground-level wind caused by instability is self-limiting, these winds tend to destroy the atmospheric instability that caused them. n Strong winds provide good mixing, both horizontal and vertical, which makes the temperature gradient approach the dry adiabatic gradient....
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This note was uploaded on 10/14/2011 for the course CIVL CIVL345 taught by Professor Hsinchu during the Spring '11 term at SUNY College of Environmental Science and Forestry.

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Meteorology for Air Pollution Control Engineers27 - 3 n...

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