Regional Surface Fluxes From Remotely Sensed Skin Temperature and Lower Boundary Layer Measurements

Abstract

During First International Satellite Land Surface Climatology Project Field Experiment in north‐eastern Kansas, surface temperature was measured by infrared radiation thermometers at some 12 stations spread over the 15 × 15 km experimental area. These data, together with wind and temperature profiles in the unstable atmospheric boundary layer measured by means of radiosondes, were analyzed within the framework of Monin‐Obukhov similarity. The radiometric scalar roughness corresponding to the radiometric surface temperature was found to increase as the season progressed; for the spring campaign the mean value was z oh,r = 4.56 × 10 −7 m and for the fall z oh, r = 1.01 × 10 −2 m. The radiometric scalar roughness could also be expressed as a function of solar elevation and to a lesser extent, of canopy height or leaf area index. For an elevation range 10° ≤ α ≤ 75° the regression equation is z oh,r = exp [−0.735 ‐ 3.61 tan (α)]. With this function good agreement ( r = 0.87) was obtained between the profile‐derived regional surface flux of sensible heat and the mean flux measured independently at ground‐based stations under unstable conditions. Similarly, regional values of evaporation, obtained by means of the energy budget method from these sensible heat flux estimates, were in good agreement ( r = 0.96).