Regional‐Scale Estimates of Surface Moisture Availability from GOES Infrared Satellite Measurements1

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Abstract
A method for obtaining remotely a measure of surface moisture, called moisture availability, is derived here using satellite infrared surface temperature measurements in conjunction with a numerical boundary layer model. Results are presented largely in the form of a statistical comparison between rainfall (antecedent precipitation index) and soil moisture patterns. Moisture availability patterns were determined from Geostationary Operational Environmental Satellite (GOES) thermal infrared temperature measurements for 12 days during the dry summers of 1978 and 1980 over eastern Kansas and southeastern Nebraska. Representative analyses of moisture availability are presented, along with a summary of results for all cases. A significant correlation was found between M and the antecedent precipitation (API) for virtually all 12 days analyzed. The relationship between M and API can be expressed as a log‐linear one: API (cm) = 0.32 (2a, where n = a + bM and a ∼ 0.9 and b ∼ 2.2. Agreement between M and API was poorest on the smallest scales, for reasons which are discussed in the text. The relatively narrow range of API values over which M is sensitive to changes in rainfall suggest that the infrared method is most suitable for deriving surface moisture availability over plains or semiarid vegetation and where there are large horizontal precipitation gradients. The accuracy of the method may permit inference of percent soil moisture over the rooting depth of plants to within plus or minus 10 to 20%, at least when averaged over a regional‐scale domain.
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