Submitted to: Scaling Up Hydrological Variables Using Remote Sensing
Publication Type: Proceedings
Publication Acceptance Date: June 3, 1996
Publication Date: N/A
Technical Abstract: Soil moisture is a highly variable quantity in both space and time. The objective of this paper is to describe the spatial variability from the field scale with in-situ measurements to the regional scale with remotely sensed measurements. The typical field scale result is that the coefficient of variation for a large number (greater than 10) of samples is between 10 and 25 percent, which has implications for our ability to calibrate our remotely sensed measurements at the field scale. At this scale the variability appears to be random in nature. When the averaging is done over larger areas, there appears to be some reduction in this variability. For example in the Washita 92 experiment, when the average of all the in-situ soil moisture observations was compared to average brightness temperature for each day, a smooth result was found. When the comparison is done on a field by field basis, considerable scatter is observed. At the regional scale the variability is related more to the larger scale variations in soils, topography and rainfall. Examples of these can be seen in remotely sensed results from Monsoon 90, Washita 92 and HAPEX-Sahel.