DECOUPLING OF SURFACE AND NEAR-SURFACE SOIL-WATER CONTENT - A REMOTE-SENSING PERSPECTIVE

Inconsistencies between remotely sensed (thermal infrared), in situ, a nd modeled values of soil water content are examined. First, an import ant hydraulic parameter in a soil water profile model is varied by one standard deviation to simulate a reasonable degree of spatial variabi lity within a given soil texture class. This results in a large range of drying rates at the soil surface and the formation of a sharp verti cal soil water gradient at the surface. The formation of this gradient is dependent upon the soil properties. Thermal infrared remote sensin g, which detects soil moisture at the soil surface, is then discussed in this context. Because of the ''decoupling'' of the soil water profi le, we conclude that soil moisture derived from surface radiant temper atures is probably not useful in knowing the column-average soil water content but may provide some insight into the spatial variations in s oil texture and hydraulic properties at the surface.