EFFECT OF RANGE ON APPARENT HEIGHT AND FREQUENCY OF HIGH-ALTITUDE RADAR PRECIPITATION ECHOES

Abstract

Overestimation of the height of radar precipitation echoes increases with horizontal distance from the WSR-57 radar as a result of the combined effect of earth curvature, atmospheric refraction, and beam width. Radar operating procedures include altitude corrections for these effects. It has been suspected that even after application of these corrections, a bias exists toward higher echoes and greater-than-expected frequencies with increasing distance from the radar. In this paper, empirical estimates of the magnitude of the errors in echo altitude have been determined by regression techniques for 13 WSR-57 radar stations. For echoes ≥50,000 ft, the average echo altitude increase is less than 1,000 ft for distances up to 100 mi. It was also found that echo frequencies increase proportionally with the area of each additional 10-mi annulus. Consequently, errors in echo altitude and frequency of occurrence due to range effects should be considered insignificant for distances out to 100 mi for the WSR-57 radar.