Coupled heat and vapor transport: The thermostat effect of a freely evaporating land surface

Abstract

Analytical solutions of the 2-D heat and vapor transport equations for a surface moisture jump are often based on a constant streamwise temperature (Tws) assumption over the wet vegetated surface. By analyzing 90 thermal infrared images taken over center-pivot irrigated areas in Nebraska, it has been demonstrated for the first time that such an assumption is realistic. Average temperature difference between the perimeter and core of the irrigated full or half circles stayed between -0.11 and 0.09°C (standard deviation of 0.25-0.41°C). It was further demonstrated that wet-bulb temperatures (a proxy of Tws) remain near constant during drying of the environment when net radiation and wind conditions stay largely unchanged, enabling estimation of Tws at any stage of drying, thus improving evaporation estimates of the Priestley-Taylor equation in arid and semiarid environments. ©2014. American Geophysical Union. All Rights Reserved.