BASIN-SCALE SOLAR IRRADIANCE ESTIMATES IN SEMIARID REGIONS USING GOES7

Semiarid regions exhibit large temporal and spatial variability in sur face conditions and, therefore, pose a challenge for estimating compon ents of the surface energy budget. In particular, it is difficult to e stimate the evapotranspiration component of the hydrological cycle. Be cause evapotranspiration is strongly controlled by absorbed solar radi ation, an attempt has been made here to evaluate the accuracy at which the downward shortwave irradiance (SW down) can be estimated from sat ellites on basin scale. It was demonstrated that even under highly var iable cloud conditions, satellite estimates of SW down daily means wer e within 10% of measured values, while 5-day means were within 3% of m easured values. Such accuracies are of relevance for hydrological mode ling at watershed and basin scales.