Wind Shear

Wind velocity increases with altitude and wind moving close to Earth's surface is slowed down by obstructions like buildings, trees and similar. Wind slow down along the surface is "wind shear".

Wind shear can be expressed as

v / v_o = (h / h_o)^α                                             (1)

where

v = the wind speed at height h (m/s)

v_o = the wind speed at height h_o (m/s)

α = the wind shear exponent

The wind shear exponent varies with the terrain.

Example - Wind Speed in a Terrain with Several Buildings

With a Wind Shear Exponent 0.25 and wind velocity at level 10 m measured to 5 m/s -  wind sped at level 40 m can be estimated by transforming (1)

v = (h / h_o)^α v_o                                            (1b)

Substituting with values

v = ((40 m) / (10 m))^0.25 (5 m/s)

    = 7.1 m/s

Temperature ^oC
K
^oF

Length m
km
in
ft
yards
miles
naut miles

Area m²
km²
in²
ft²
miles²
acres

Volume m³
liters
in³
ft³
us gal

Weight kg_f
N
lbf

Velocity m/s
km/h
ft/min
ft/s
mph
knots

Pressure Pa
bar
mm H₂O
kg/cm²
psi
inches H₂O

Flow m³/s
m³/h
US gpm
cfm