SATELLITE INTERPRETATION DISCUSSION NOAA/NESDIS  Regional and Mesoscale Meteorology Team Cooperative Institute for Research in the Atmosphere (CIRA) Colorado State University   Fort Collins, Colorado March 8, 2000

Detection of fog using GOES 10 imagery   Figure 1 xxxx The focus of this discussion is the detection of fog using GOES 10 imagery.  Figure 1 is the fog product.  The fog product combines the 4 km resolution infrared (10.7 micron) and short wave infrared (3.9 micron)  channels to take advantage of the emissivity difference between liquid water and ice at the two wavelengths.  Liquid clouds appear in lighter shades,  while ice clouds and snow appear dark.  Figure 1 shows the fog in central CO, eastern CO, and western NE.  A low pressure system in KS has a combination of light and dark pixels due to the presence of both ice and liquid phase clouds contained within the storm.  Click on images to enlarge   Figure 2 Figure 3   Figure 2 shows the 4 km resolution 3.9 micron channel, and although the fog and ice clouds are still discernible, it does not do as well as the fog product in contrasting between the low clouds and ground.  Figure 3 shows the 4-km resolution 10.7 micron channel image.  The red enhancements in Figure 3 are -40 C, and all other colors are colder than -40 C.  Figure 3 indicates that the temperature of the clouds in the low in KS are cold relative to the fog in NE and CO.  Note that the fog and ground have similar temperatures at 10.7 microns making it difficult to discern the ground from the fog and low stratus.        Figure 4 xxxx Figure 4 is the 1 km resolution visible image.  The visible imagery shows more detail of the cloud structure, but is not helpful in discerning the phase of the clouds.

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