Preliminary results of ground-based rain measurements with a dual-frequency multiparameter radar-radiometer

Since 1985, a dual-frequency radar-radiometer, built by the Communications Research Laboratory of Japan, has been flown in several NASA-related experiments to test and to develop methods for the estimation of rain rate from space. These measurements have proved useful for developing and justifying methods of rain estimation for the radar to be launched as part of the Tropical Rainfall Measuring Mission. Over this period of time, the instrument was modified to provide, in addition to the usual copolarized data, cross-polarized measurements at X-band (10 GHz) and Ka-band (34.45 GHz). Additional upgrades have been completed to enable measurements of linear depolarization ratio (L_DR) and differential reflectivity ratio (Z_DR) at both frequencies for ground-based observations. Plans are presently underway to combine these measurements with the S-band Spandar radar and the microwave and millimeter-wave link experiments located at Wallops Flight Facility. In this paper, the authors first describe the instrument modifications, then present results taken during a case of light stratiform rain case. Because the calibration of the system is not yet complete, the authors focus on some of the quantitative features of the data obtained at and near the melting layer