24-26 October 1997 Winter Storm
Snow Cover, Low Cloud Detection

GOES-8 visible

26 October -- GOES-8 visible

Animations: Java | QuickTime

GOES-8 IR channel 2

26 October -- GOES-8 IR channel 2

Animations: Java | QuickTime

Interactive dual-image comparison (visible and shortwave IR)

The GOES-8 visible and IR channel 2 (shortwave infrared) imagery above and below show the areal extent of snow cover left in the wake of the 24-26 October 1997 winter storm. Many snowfall records were set by this storm, including 24 inches at Denver CO, 19.9 inches at Colorado Springs CO, 19.5 inches Goodland KS, 17.4 inches at Hastings NE, 13.2 inches at Lincoln NE, 9.5 inches at Omaha NE, 6.6 inches at Des Moines IA, and 3.8 inches at Madison WI. The arctic air which surged southward behind this system also set several temperature records, including -10 F at Laramie WY, 3 F at Hill City KS, 4 F at Hastings NE, 7 F at Yuma CO, and 10 F at Goodland KS.

Snow cover is often easy to identify on visible imagery due to the appearance of unfrozen rivers and topographical features such as mountain ranges (snow cover also remains stationary in an image animation, while cloud features tend to move and evolve). However, on each of the two days shown there were several patches of low cloud (stratiform cloud comprised of water droplets) over and near the areas of significant snow cover. These low clouds show up as darker (warmer) features on the shortwave IR imagery due to the enhanced reflectivity of the liquid cloud droplets (in addition to the IR channel 2 sensitivity to reflected solar radiation off the cloud tops). The snow cover appears slightly brighter (colder) than the surrounding snow-free terrain since snow (as well as ice cloud) is a poor reflector of the 3.9 micrometer wavelength radiation detected by IR channel 2. Another example of snow cover and low cloud detection using GOES-9 imagery from this storm can be found at the CIRA Daily Satellite Discussion.

GOES-8 visible

27 October -- GOES-8 visible

Animations: Java | QuickTime

GOES-8 IR channel 2

27 October -- GOES-8 IR channel 2

Animations: Java | QuickTime

Interactive dual-image comparison (visible and shortwave IR)


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