Snow

Knowledge of surface geography together with an appreciation of the climatological variation of snow cover through the seasons is a basic prerequisite for the analysis of satellite imagery in respect of snow.

The tone of snow on VIS imagery varies from bright white to light grey depending on the nature of the relief, vegetation, the age of snow and the illumination. In areas of relatively flat terrain without trees snow surfaces appear uniformly white in tone. In areas covered by extensive forests a snow-covered surface appears patchy, brighter patches correspond to areas where there are no trees and dark patches to forest areas.

In IR imagery, snow covered terrain often appears whiter than its surroundings. At night the snow surface cools more rapidly than its surroundings and during the day it warms gradually. Light snow on the tops of high mountain ranges is less detectable in IR than in VIS data as the temperature difference between cold land and snow is small while the difference in albedo between snow and land is large.

0 0

Post a comment