Winds over saltcedar

Abstract

An analysis of hourly wind speeds above and within a stand of saltcedar near Buckeye, Arizona, reveals that in 90% of all observed cases, the wind profiles above the stand can be represented by the simple logarithmic equation: u z = u* k 1 n "> uz=u*k1n ( z z 0 ) "> zz0) where u z is the velocity at height z. The roughness length (z 0 ), (disregarding zero displacement), varies with a stability ratio similar to Richardson's number. The friction velocity, u* , depends on the wind speeds above the vegetation. Von Karman's constant, k, equals 0.41. Within the thickets there is considerable turbulence, and irregular wind inversions occur during daylight hours. The results are important for estimating water losses by evapotranspiration by either the energy-budget or the mass-transfer formulae.