Improving spaceborne precipitation radar retrievals in complex terrain

This study will examine several issues in measuring and attenuation-correcting radar reflectivity from space in complex terrain, with the goal of improving these important and unique measurements, and establish best practices for the upcoming Global Precipitation Mission (GPM). We will examine retrievals in 1C21 and 2A25 version 6 and 7 of Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) radar reflectivity and rainfall estimates.

Results indicate that the digital elevation model used in version 6 of the TRMM retrievals, developed circa 1994, was inadequate to provide the PR algorithms with sufficiently correct elevation information to correctly identify surface return and correctly remove clutter, so several regions where the digital elevation model was of poor quality contain non-meteorological echo in version 6 reflectivity and rainfall products. The height of the lowest retrieved bin was found to vary by more than 2 km across the swath, such that potentially useful bins with meteorological echo in 1C21 are discarded. An on-line method for surface clutter rejection is proposed. The quality of path-integrated attenuation estimates from the surface reference technique versus Hitchfeld-Bordan techniques are also compared in complex terrain. Finally, the DSD assumptions in orographic precipitation are scrutinized with available DSD measurements in the literature. Version 7 products will be scrutinized in a similar way, including algorithm changes were implemented, and the implications of an improved digital elevation model was used by NASA at the suggestion of the author.