Dramatic contrast between low clouds and snow cover in daytime 3.7 micrometer imagery.

Abstract

A long-standing problem in satellite meteorology has been the discrimination of low clouds from snow cover. The basic difficulty is that clouds and snow have very similar radiometric properties in regions of the electromagnetic spectrum most often used for observation. In the visible window (near 0.5 micrometer) both clouds and snow have high albedos; in the 11 micrometer infrared window both clouds and snow have high emittances. Thus, low clouds and snow, which have similar thermometric temperatures, present little contrast in visible or 11 micrometer infrared satellite images. In the 3.7 micrometer window, however, clouds and snow can have different radiometric properties.-Authors