Correlation of Cloud Brightness and Radiance with Precipitation Intensity.
Final rept. Jul 74-Sep 75 on Task B,
STANFORD RESEARCH INST MENLO PARK CALIF
Pagination or Media Count:
The objective of this study was to determine the extent to which a combination of satellite measurements of visual cloud brightness and infrared radiance indicates the presence and intensity of precipitation within a cloud. The study was made using digitized data on cloud brightness and radiance from one of the Defense Meteorological Satellite Program satellites and digitized radar data from ground-based weather radars. Two comparisons of clouds and radar data were made. The first related cloud brightness and radiance over a large area to the combined average precipitation rate of all the radar echoes within the area. The second related cloud brightness, radiance, and precipitation statistics for a number of selected small areas of clouds and echoes on a given date. The comparisons showed that, while precipitation intensity appeared to increase with increasing brightness and radiance on a given day, no specific brightness and radiance threshold for distinguishing between precipitation-no precipitation could be selected that would be applicable to days with differing types of cloud cover. Thus, to use brightness and radiance as indicators of precipitation intensity, it is necessary to determine the average brightness and radiance for the type of cloud cover a large area and then infer precipitation within smaller areas on the basis of the departures of brightness and radiance of the small areas from those of the large areas.