Investigation of polarimetric measurements of rainfall at close and distant ranges.

Abstract

As part of continuous modernization of operational weather radar systems, several government agencies have explored adding polarimetric capability to existing networks. Polarimetric measurements of rain have been previously shown robust with respect to drop size distribution variations, hail contamination, and offer improved echo classification capabilities. Other advantages of polarimetric measurements of rain include an immunity to radar miscalibration, attenuation in rain and partial beam blockage.

This study is motivated by the lack of validation for polarimetric rainfall applications with respect to coverage and accuracy demands of the operational weather community. To address these concerns, the quality of polarimetric measurements and rainfall estimation is investigated over a broad range of distances. Several new methods to identify regions of known radar bias and improve radar rainfall measurements in operations are provided.

Whereas the existing literature overwhelmingly recommends polarimetric methods for weather radar applications, the majority of dual-polarization studies have been conducted on datasets collected at relatively close distance to the radar. However, it is well-known that the quality of radar measurements and rainfall estimates degrades with distance due to factors including beam broadening, the effect of Earth curvature and the overshooting of precipitation.