Regional heat flux over the NOPEX area estimated from the evolution of the mixed-layer

The atmospheric mixed layer grows in response to regional turbulent fluxes, including the aggregation of small-scale processes. In this study, a method to determine the regional integrated sensible heat flux from information on the evolution of the mixed layer over the Northern hemisphere climate-Processes land-surface Experiment (NOPEX) area is derived, which is applicable when the mixed-layer height is well above the layer. The data required can be derived from wind speed and temperature profiles obtained by radiosoundings. As illustration, the method is used to estimate the regional heat flux over the NOPEX area for 3 d in 1994. Results show that the heat fluxes at the two agricultural sites are comparable, both showing the characteristic daily cycle of a maximum around noon. The heat flux at the forest sites reaches two to three times higher values than at the agricultural sites.