Sensitivity of Surface Varables to Changes in Physical Soil Properties: Imitations to Thermal Remote Sensing of Bare Soils

A numerical simulation model (SALSA), in which the mutual interactions between soil and atmosphere are simulated, was used to determine the sensitivity of bare soil surface temperature to variations in physical soil properties and roughness length. Also, sensitivity of air temperature, saturation deficit, and evaporation rate to surface properties were analyzed. Results are presented for two distinguished stages of drying. Analyses of variance and covariance were used to study the simulation results that were obtained by varying parameters in a full two-level perturbation scheme. The possibilities of estimating evaporation rate from thermal imagery are discussed and were found to be very limited. It was concluded that albedo, dry toplayer thickness, roughness length, and vapor diffusivity do have the strongest influence on surface temperature during the day, whereas thermal inertia predominates during the night. In thermal surveys of the moisture regime of bare soils, simultaneous determination of albedo is considered indispensable.