Jielun Sun & L. Mahrt/Abstract ATM-9417959 The surface radiative temperature is the only available surface temperature in most large scale field programs and is therefore used to estimate the vertical temperature difference in the bulk aerodynamic relationship. In many numerical models, the vertical temperature difference is estimated in terms of radiative surface temperature computed from the surface energy balance. Both of these applications generally retain existing similarity theory even though such similarity theory is appropriate only for the temperature at the roughness height. Several recent studies have shown that the combination of surface radiative temperature with existing similarity theory can lead to large errors, counter gradient fluxes and/or absurdly small values of the roughness height for heat. This document research proposes to ameliorate these problems by considering modification of existing similarity theory and relationships between the surface radiation temperature and the aerodynamic surface temperature. These developments must be preceded by replacing the value of the surface radiative temperature with a function of the microscale distribution of the surface radiative temperature. As one example, appropriate weighting of the temperature of hot dry ground, partially covered by transpiring vegetation, should eliminate cases of countergradient heat transport. Several models and measurement schemes or representing the microscale distribution of surface radiation temperature are proposed. The data analysis will take advantage of existing tower and aircraft observations from a number of field programs. In addition, more focused measurements of the microscale distribution of surface radiative temperature will be implemented along with flux measurements from the NCAR ASTER System. The bulk aerodynamic formulation will be re-evaluated in terms of the improved representation of the surface radiation temperature. Special attention will be given to problems associated with the free convection case of nearly vanishing mean flow and the case of spatially- averaged fluxes under weak wind conditions.
