Rainfall estimation from VU C-band polarimetric radar measurements

Polarimetric radars provide information on the size, concentration, shape, orientation and phase of the precipitation. It has been shown that the rainfall estimation algorithms using polarimetric radars measurements are more accurate than the classical R-Z relationships. In addition, polarimetic radars are also able to correct for attenuation and differential attenuation from rain. At C-band, attenuation and differential attenuation can be an important issue, especially in regions behind a strong rain area hidden from the radar point of view.

The objective of this study is to estimate the rainfall rate (R) and total rainfall produced by a storm on 18 July 2010. We will first use an algorithm based on the differential phase shift (ÔDP) to correct Zh and ZDR for attenuation and differential attenuation. In the next step, we use three different relationships between rain rate and polarimetric variables ( R(KDP,ZDR), R(Zh,ZDR), R(KDP) ) to calculate an instantaneous rain rate map. Finally we calculate the total rainfall produced by the storm and use ground observations for validation of the method. This will allow us to determine the best rain rate algorithm according to rain regime (convective, stratiform).

This work was partially funded by MIT Lincoln Laboratory's NEXRAD Enhancements Program for the FAA.