Polarimetric radar remote sensing of rainfall and liquid water in clouds

This study focuses on investigation, development and evaluation of dual linear polarization radar techniques for measuring rainfall rates and liquid water content in clouds. The differential reflectivity ({dollar}Zsb{lcub}DR{rcub}{dollar}) technique and two well-known Z-R relationships (Marshall-Palmer and Jones' Thunderstorm) are evaluated through a case study which compares radar and ground-based raingauge measurements utilizing data from the MAYPOLE (1984) experiments conducted in Colorado. The horizontal storm motion and vertical transport of raindrops, as well as the consistency of the spatial and temporal averaging of the radar and raingauge data are taken into account. It is observed that the {dollar}Zsb{lcub}DR{rcub}{dollar} technique performs consistently well in the estimation of rainfall rate R when compared with raingauges at two different locations in the storm.; A cross correlation technique is proposed and applied to translating radar measurements of rainfall parameters from aloft to their corresponding ground values. Dual polarization radar measurements obtained during the MIST (1986) experiments in Alabama are utilized for this purpose. This technique is also used to estimate the storm motion direction which is necessary for the radar-raingauge comparative studies. One- and two-dimensional correlation lengths of the reflectivity factor, rainfall rate and median volume diameter fields are presented for rainfall events from both MAYPOLE and MIST experiments.; Scattering and propagation properties of millimeter waves (94 and 140 GHz) in rainfall are also studied. Power law relationships based on the Marshall-Palmer drop size distribution are derived for rainfall rate R and the propagation parameters such as specific attenuation, specific differential attenuation and phase shift. It is proposed that these parameters at 94 and 140 GHz can be used for estimating path integrated rainfall rates over short propagation paths less than a few kilometers. Raindrop shape models are also shown to significantly affect the interpretation of the Doppler velocity spectrum for vertically pointing radars.; A dual polarization bistatic scattering technique is proposed and illustrated for estimating cloud and fog droplet size distributions and their liquid water contents. (Abstract shortened with permission of author.)...