Problems of deducing the soil water balance in dryland regions from Meteosat data

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Abstract
Meteosat is a geostationary satellite which observes the earth from the same point every half hour and views many of the drylands of Africa. Its data can be processed to provide information on the state of the surface of the earth, and its moisture condition in particular, by evaluating the thermal inertia from observations of the diurnal temperature cycle of the surface. This method is limited by the simple radiometry and low spatial resolution of Meteosat. The surface temperature amplitude cannot be known to better than 2°C, and the heat flow into the ground to 20%. As a result the actual values of thermal inertia can be known only to this accuracy.Interpretation of thermal inertia is ambiguous, and alternative interpretations of any given value are discussed, showing little information on conditions more than 10 cm below the surface, and limited discrimination over soil moisture contents even in the topmost layer. Despite these difficulties, thermal inertia values could be calculated routinely. This could give information on the detailed distribution of rain from convective storms for agricultural monitoring and for large‐scale meteorological models.