Effect of vegetation density on the parameterization of scalar roughness to estimate spatially distributed sensible heat fluxes

The First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE) was initiated in part to explore methods ro improve our ability to estimate spatially distributed heat fluxes over hilly prairie. In this research, spatially distributed, remotely sensed surface temperatures and surface-based measurements of leaf area index, wind speed, and air temperature were used in a Monin-Obukhov type similarity formulation to calculate sensible heat fluxes (H-c). Use of Monin-Obukhov type similarity required that a parameterization for scalar roughness of sensible heat be developed. Several methods were examined including a linearized version, with respect to leaf area index, of an earlier theoretical expression of scalar roughness for grass-like vegetation. Comparison between measured and parameterized scalar roughness values gave a correlation of r = 0.828. This parameterization was used with data measured on July 11, 1987, under conditions of strong solar heating, high winds, and fairly uniform soil moisture, to calculate H-c values at an array of 10 surface flux stations. A spatial comparison between H-c and measured sensible heat fluxes yielded good agreement with a correlation coefficient of 0.878 and a root-mean-square error of 31.1 Wm(-2).