ACTIVE AND PASSIVE REMOTE-SENSING OF PRECIPITATING STORMS DURING CAPE.2. INTERCOMPARISON OF PRECIPITATION RETRIEVALS OVER LAND FROM AMPR RADIOMETER AND CP-2 RADAR

One of the recent campaigns devoted to precipitation studies using bot h active and passive microwave remote sensing systems was the Convecti on and Precipitation/Electrification Experiment (CaPE), which took pla ce in central Florida during the summer of 1991. During CaPE, the airb orne Advanced Microwave Precipitation Radiometer (AMPR), having four c hannels at 10.7, 19.35, 37.1 and 85.5 GHz and the National Center for Atmospheric Research CP-2 multiparameter radar at S-band (3 GHz) and X -band (10 GHz) were operated simultaneously. In this paper, we compare estimated hydrometeor liquid/ice water contents and surface rainrates , both retrieved from the AMPR radiometer and CP-2 radar measurements, for a case study consisting of a heavy precipitating storm over land near Cape Canaveral on August 12, 1998. The multi-frequency radiometer -based retrieval scheme uses a cloud-precipitation dataset generated f rom a cloud model and extended by a physically-constrianed Monte Carlo procedure, along with a discrete-ordinate radiative transfer model an d a principal component statistical technique to help formulate non-li near regression equations for the sought-after hydrometeor quantities. By applying linear discriminant analysis, the algorithm is used to es timate column integrated liquid/ice water contents, as well as the ver tical profiles of these quantities to within a specified accuracy. Rai nfall rates are estimated either by non-linear regression or by a suit able fallout model. The analysis has confined itself to along-track na dir-looking AMPR measurements to avoid complications with variable pol arization mixing and geometric distortion for off-nadir observations. Considering the different model assumptions used in the two types of r etrieval algorithms and the diverse geophysical information content wi thin the two types of measurements, substantial agreement between the radar- and radiometer-derived retrievals has been achieved for the col umnar liquid/ice water contents and rainrates.