Wind
Velocity
Wind velocity is an important variable in the study of transport of air
pollutants from a source. Considerable efforts have been spent to measure
wind velocity and to develop equations for computing wind speed. A power
law profile is generally used to describe the variation of wind speed with
height in the surface boundary layer.
where U1 is the velocity at z1 (usually 10 m) and
U is the velocity at height z. The values of p are given in the following
table.
Table: Exponent for wind profile used in the ISC model
|
Stability Class
|
Rural p
|
Urban p
|
| A - Very Unstable |
0.07
|
0.15
|
| B - Moderately Unstable |
0.07
|
0.15
|
| C - Slightly Unstable |
0.10
|
0.20
|
| D - Neutral |
0.15
|
0.25
|
| E - Moderately Stable |
0.35
|
0.30
|
| F - Very Stable |
0.55
|
0.30
|