Evaluation of the TRMM PR Algorithms in Complex Terrain

In this study, the performance of the version 6 Tropical Rainfall Measuring Mission precipitation radar (PR) in complex terrain will be examined. The PR was the first spaceborne radar designed for precipitation retrieval, and over the years the standard PR algorithms (1C21, 2A25) have been continuously improved to provide unprecedented views of the 4-D structure of precipitation. As such, the PR products remain the “gold standard” over land in terms of spaceborne instantaneous precipitation retrieval, and thus quantifying uncertainties in reflectivity and rainfall retrieval in regions where the PR retrieval algorithms are likely challenged by the complex topography is an important exercise. This investigation will center around two issues that the PR algorithms consider: (1) attenuation correction, drop size distribution and Z-R relationship selection, and rainfall retrieval, and (2) mainlobe and sidelobe clutter ranges and terrain masking. To address (1), the PR algorithms' assumptions will be examined in the context of ground-based radar and disdrometer measurements of precipitation characteristics in complex terrain. For (2), we will examine the PR level 1 and 2 retrievals next to high resolution digital terrain models, as well as perform comparisons with CloudSat (which has higher spatial resolution and thus reduced clutter) to examine light and shallow precipitation that the coarser resolution PR may miss, and examine the PR's assumptions regarding the vertical profile of precipitation near the surface. The implications of these results for future active remote sensing missions will be discussed.