SATELLITE 

INTERPRETATION 

DISCUSSION 
 NOAA  NESDIS 
 Regional and Mesoscale 
Meteorology Team
Cooperative Institute for Research in the Atmosphere (CIRA)
 Colorado State University  Fort Collins, Colorado
November 13, 1998 
 Figure 1   Visible Channel
 Today’s satellite discussion focuses on a benefit of using the reflectivity product compared to the 3.9 micrometer imagery. The feature of interest is the western edge of the stratus deck found along eastern CO and NM as seen in the visible imagery (Figure 1).  Figure 2 shows the reflectivity product for the same area and time as Figure 1.  Note that the western edge of the stratus deck has excellent contrast with the ground using the reflectivity product.  Figure 3 shows the 3.9 micrometer image and it does not reveal the western edge of the stratus as well as the reflectivity product.  (Click on images for full display.)
  
 
Figure 2   Reflectivity Product
  
Figure 3   3.9 Micrometer Channel
  
At 3.9 micrometers, the stratus and ground have approximately the same brightness temperature, hence their poor contrast.  The brightnesses are approximately the same for the following reason.  The ground has a large emitted component and a small reflected component.  The opposite situation holds for the cloud.  Although the individual contributions by emission and reflection differ between the cloud and ground, the total contribution at 3.9 micrometers is approximately the same for each feature.  Once the emitted component is removed by the reflectivity product, the resulting brightness temperature for the stratus exceeds that for the ground due to the contribution by the reflected component.
 
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