Radar based simultaneous estimates of cloud and rainfall parameters

A two-step remote sensing approach for retrievals of layer mean rainfall rates and total vertical amounts of cloud liquid and ice in a vertical column for stratiform precipitating systems is discussed. This approach uses attenuated reflectivity measurements from vertically-pointing Ka-and W-band cloud radars. Retrievals of the rain and liquid cloud parameters are based on attenuation of mm-wavelength reflectivity measurements in the liquid phase below the melting layer. The two versions of retrievals are compared. The first one uses the difference in the Ka and W –band signal attenuations in rain and clouds and the second one constrains the rainfall estimates using surface disdrometer estimates and uses W-band total attenuation for differentiating cloud liquid and rainfall. Estimates of ice phase in a vertical column above the melting layer are performed using the Ka-band reflectivity profiles which are corrected for total attenuations caused by the liquid layer and the wet radome using the nearby WSR-88D radar which operates at an S-band frequency, so its signals are practically un-attenuated in stratiform rainfall that is considered. The applicability of the suggested two-step approach is illustrated for a case study. Expected uncertainties for retrievals of cloud liquid water path are estimated at about 200-250 gram per square meter for typical rainfall rates observed in stratiform events. The ice water path retrievals uncertainties can be as high as a factor of 2. Retrieval results suggest that for typical stratiform precipitation events, ice water path values are significantly larger (by one order of magnitude or so) than liquid water path values.