MODIS False Color Separates Clouds from Snow Following the Holiday Blizzard

Following the recent blizzard in the Central Plains over the 12/23-12/26 period, the broad area of snow cover produced a region with relatively cold surface temperatures.  When low clouds are present, their brightness temperature contrasts against the warmer land surface are reduced.  Through the use of multispectral imagery and image classification, the MODIS instrument aboard Aqua or Terra can better discriminate snow cover from low clouds.  In the image below, there is little contrast among the “shades of gray” across Nebraska, South Dakota, Minnesota and Iowa, although low clouds were present.

Infrared image from MODIS (Terra) at 1748 UTC, December 28th, with little contrast between clouds and snow cover in the central United States.

Through the use of multiple spectral bands and color enhancement, snow cover in the image below is depicted in red shades, with cloud cover in white.  This color combination is able to discriminate snow from the streak of cloud cover running through the Dakotas into northern Illinois.  In the northern half of Minnesota, snow cover on the ground is likely, but forested areas dominate the landscape and mask the surface snow cover in many areas.  Shades of blue indicate snow-free land areas in western Oklahoma, portions of Kansas and eastern Colorado.

False color composite from MODIS (Terra) at 1748 UTC, December 28, highlighting the area of snow (red) versus cloud cover (white) or snow free terrain (blue).

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