Comparative utility of microwave and shortwave satellite data for all-weather charting of snow cover

Abstract

Charting snow cover by shortwave imaging requires visual analysis which is complicated by cloud coverage and poor surface illumination1,2. Microwaves, however, being almost unaffected by clouds and independent of solar illumination, are potentially useful for monitoring the extent and variation in snow cover, in climatological and hydrological studies. Data from spaceborne passive microwave sensors have previously been used to chart regional overland snow cover3–5; but charting hemispherical snow coverage was not feasible until high spatial resolution and multiple channels were combined in the Scanning Multichannel Microwave Radiometer (SMMR) launched in 1978 on the Nimbus-7 satellite. Here we compare SMMR data with shortwave images obtained over Asia to justify further use of microwave sensors in automated charting of seasonal snow cover under all weather conditions. Agreement between the two methods is found in ∼75% of the tested grid points.