A Comparison between the Height of Cumulus Clouds and the Height of Radar Echoes Received from Them1

Abstract

A comparison is made between the angular elevation of the visible top of a cloud tower and the top of the radar echo associated with it. Employing a 10-cm WSR-57 radar, we find angular differences between 0 and +1° with the radar elevation higher. Our sample is 32 clouds with cops from 16,000 to 53,000 ft at ranges between 10 and 35 n mi in the vicinity of Miami, Fla. From the known sensitivity of the radar we have deduced that in the upper 500—1500 ft of these clouds the average equivalent reflectivity factor Z has values between a few tenths and a few mm⁶m⁻². Because of these low values when the conventional beam-width correction is made, the height of the visible top exceeds that of the radar top by 200–3000 ft.