Variations in the energy budget above growing wheat and barley, Ilstorp 1998 : a gradient-profile approach

Abstract: Fluxes of sensible heat and latent heat were calculated above fields of barley and wheat in Ilstorp, using a gradient profile approach. Gradient Richardson’s number was used as the stability parameter, and it was shown that atmospheric stability varies both with time of the day and wind speed. Temperature and wind profiles were studied, and it was possible to detect a rise in the active surface in relation to increasing crop height. Displacement heights and roughness lengths were calculated for separate periods of time. The connection between these parameters and crop height was perhaps not as simple as predicted. The results were used to estimate the energy budget above growing crop; encompassing net radiation, sensible heat, latent heat and soil heat fluxes. It was found that, in the beginning of the season, latent heat flux dominated the energy balance budget. As the crop matured and turned yellow, crop height decreased slightly, and the sensible heat flux now increased above the latent heat flux. Soil heat flux remained quite constant during the summer, around 0 to 15 W m-2.