Quantitative intercomparison of polarimetric ground radar and TRMM PR observations

The Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) is a spaceborne radar operating in a nearly circular orbit at 350 km altitude with 35 degrees inclination and period of about 91.5 minutes. Simultaneous comparisons of radar observations were made between the National Center for Atmospheric Research (NCAR) S-POL radar and TRMM PR during the TExas and FLorida UNderflights (TEFLUN-B) campaign that took place near Melbourne, FL in 1998, and the Large Biosphere-Atmosphere experiment in Amazonia (LBA) near Ji-Parana, Brazil in 1999. Though direct intercomparison between space and ground radar observations is, in principle, straight forward, differences in viewing aspects between space and Earth point observations, propagation frequencies, resolution volume size and time synchronization mismatch between instrument measurements can contribute, in a significant way, to intercomparison errors and should be taken into account. Vertical profile of polarimetric radar variables, namely, reflectivity (Z/sub h/), differential reflectivity (Z/sub dr/), specific differential phase (K/sub dp/), cross-correlation coefficient (/spl rho//sub co/) and linear depolarization ratio (LDR) are used to describe the precipitation characteristics through the TRMM PR beam. These observations are, in turn, used to determine the type of hydrometeor along the PR beam using a fuzzy-logic technique.