95-GHz Polarimetric Radar Measurements of Orographic Cap Clouds

Abstract

The use of millimeter-wavelength radars for cloud microphysical research was investigated in experiments at the Elk Mountain Observatory near Laramie, Wyoming, between April 1990 and March 1992. The 95-GHz polarimetric radar used in these experiments is a portable, high-power, dual-polarization radar capable of characterizing the complex scattering matrix in two pulses. The scatterer's polarimetric response is characterized in terms of the Mueller matrix, a form that is seen to be convenient for computing the response of a scatterer for any arbitrary combination of transmit and receive antenna polarizations. This paper summarizes the results of recent experiments carried out at the Elk Mountain Observatory. Polarimetric data from orographic cap clouds are found to be sensitive to ice-particle orientation and composition. Comparison of radar-observed reflectivities with those computed from in situ images shows good agreement if the volume fraction of ice in ice-air mixtures is taken into account.