Regional Flux Estimation in a Convective Boundary Layer Using a Conservation Approach

Abstract

During the Southern Great Plains 1997 Hydrology Experiment, a tethersonde system was deployed at the U.S. Department of Energy?s Atmospheric Radiation Measurement Cloud and Radiation Test Bed (ARM CART) central facility. Additional measurements included several surface flux stations at the central facility and radiosondes at the ARM CART central and boundary facilities. Combined, these data support an examination of regional flux estimates obtained via the atmospheric boundary layer conservation approach. Because the tethersonde was deployed successfully only under light to moderate wind conditions, the effects of advection on estimation of regional fluxes generally are found to be small. Consistent with previous studies, direct estimation of the sensible heat flux yields more accuracy than direct estimation of the latent heat flux. Use of available energy measured at surface flux stations along with the direct sensible heat flux estimates yields latent heat estimates of similar accuracy to those obtained for the sensible heat flux. It is observed that variability in the entrainment parameter exhibits a considerable diurnal cycle, presumably related to the interplay between buoyant and shear production of turbulent kinetic energy near the entrainment zone.