Estimations of ice content of precipitating clouds using operational WSR-88D data

An approach to retrieve the total amount of ice in a vertical atmospheric column in precipitating clouds observed by the operational Weather Surveillance Radar-1988 Doppler (WSR-88D) systems will be described. The total ice amount expressed as ice water path (IWP) is estimated using measurements obtained during standard WSR-88D scanning procedures performed when observing precipitation. WSR-88D-based IWP estimates are evaluated using dedicated cloud microphysical retrievals available from the CloudSat and auxiliary spaceborne measurements. The evaluation is performed using measurements obtained in extensive predominantly stratiform precipitation systems containing both ice hydrometeors aloft and rain near the ground. The analysis is based on closely collocated in space and time satellite and the ground-based KWGX and KSHV WSR-88D IWP retrievals. The comparison results indicate relatively high correlation between satellite and WSR-88D IWP retrievals with corresponding correlation coefficients of around 0.7. The mean relative differences between spaceborne and ground-based estimates are around 50 - 60%, which is on the order of IWP retrieval uncertainties and comparable to the differences among various operational CloudSat IWP products. The analysis performed in this study suggests that the quantitative information on ice content of precipitation systems can generally be obtained from operational WSR-88D measurements, when they perform routine scans to observe precipitation. The limitations of WSR-88D IWP estimates due to radar beam tilt restrictions and the overshooting effects due to Earth's sphericity are discussed.