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Cooperative Institute for Meteorological Satellite Studies / University of Wisconsin-Madison
CIMSS Tropical Cyclone Team
Saharan Air Layer (SAL) - Product Description

GOES Low-Level Water Vapor Imagery:
Background: This imagery is created using the 7.3 µm channel on the GOES-East satellite. This infrared low-level water vapor band is sensitive to both temperature and water vapor in the atmosphere and has a weighting function that peaks at ~620 hPa. Weighting functions describe the layer of the atmosphere from which the radiation measured by a particular satellite channel was emitted. The weighting function for the 7.3 µm channel is fairly broad and typically detects temperature and water vapor in a layer from ~300-925 hPa.
Uses: This imagery is useful for tracking low to mid-level water vapor features such as the Saharan Air Layer and mid-latitude dry air intrusions and can also be used for estimating low- to mid-level atmospheric motion vectors (AMVs).
• Due to the low altitude of the weighting function of the 7.3 µm channel, upper-level atmospheric features (e.g., tropical cyclone outflow layers and cold lows) may not be readily detectable using this imagery.

For more SAL information, please visit the SAL Background Information page.