Detection of Cirrus Clouds with UHF Wind-Profiling Radar

Abstract

Simultaneous measurements of cirrus clouds with a 404-MHz wind-profiling radar and a lidar were made to examine the sensitivity of a wind-profiling radar to cirrus clouds. The results show that a 404-MHz wind-profiling radar can detect cirrus clouds with the most ice content. Although the reflectivity of Rayleigh scatterers from cirrus clouds is comparable to that of Bragg scatterers from clear-air turbulence, the echo from cirrus clouds can be identified by applying a vertical velocity threshold method. For clouds that form a distinct layer, the velocity threshold can be estimated from the discontinuity of the vertical velocity that appeared at the lower cloud boundary. The velocities below the cloud base can be estimated to be the clear-air motion. The mean length of the crystals has been retrieved by fitting the theoretical Doppler spectrum to the measured sprectrum.