Quantification of error for polarimetric rainfall algorithms using the CP2 S-band radar in South-East Queensland, Australia

The importance of polarimetric radar for more accurate rainfall estimation is widely recognized, with upcoming operational deployment of such systems. The aim of this study is to characterise the error statistics in a comprehensive and robust way for a variety of rainfall relationships both in use and empirically derived. Data from the CP2 S-band polarimetric radar situated in Redbank Plains, Queensland, Australia, is used to determine robust combinations of estimators for more accurate rainfall estimation.

This paper applies theoretical error characteristics of polarimetric variables and propagates these through a variety of both literature-derived and empirically-determined algorithms. One-minute 2DVD disdrometer data and T Matrix scattering calculations are then used to determine theoretical and practical estimates of uncertainties. Estimators are applied to six-minute radar data for the lowest two scans for four heavy rain events during 2008 and compared to a network of 293 thirty-minute gauges and ten one-minute gauges, to examine the results of the theoretical study while noting the effect of spatial and temporal averaging. These results will then be used in combination with theory to determine the limits of accuracy for different estimators, with future applications for development of robust combinations of estimators rather than rule based selection of single estimates, to attempt to improve rainfall estimation.