Aerodynamic resistance: effect of the methods used to specify the vegetated surface roughness parameters

Abstract

The purposes of this study were to determine the surface roughness parameters for momentum (z_0m) and heat (z_0h) for bermudagrass and to examine the effect of using different criteria for selecting these surface roughness parameters on the calculation of the aerodynamic resistances. Analysis of the data collected over bermudagrass suggests; that z_0m is virtually constant at wind speeds greater than 2 m/s, but increases rapidly as wind speeds decrease below 2 m/s. For wind speeds larger than 2 m/s it resulted in an average z_0m of 0.0006 m and an average z_0h of 0.00015 m, which is about: 1/7.6 of z_0m. The use of the different criteria to specify the: surface roughness parameters; resulted in considerable differences in the calculation of the aerodynamic resistances.