Cirrus clouds ice crystal study using 33 and 95 GHz radar

Low frequency scanning radars operating near 2.8 GHz (S-band) and 5.3 GHz (C-band) are traditionally used to study severe weather and map rainfall because these systems experience low attenuation. Simulated and radar measurements presented in this research demonstrate the utility of Ka-band and W-band radars for scanning in a tropical environment.; This work presents models that predict extinction rates due to atmospheric gases for 35 GHz and 95 GHz radars as a function of elevation angle. The minimum detectable radar reflectivity (dBZ_emin) is computed for both wavelengths using radiosonde and microwave radiometer measurements. In general, sensitivity decreases with elevation angle mostly because water vapor and their corresponding highest extinction rates propagate through the lower portion of the atmosphere.; Data from the Maritime Continent Thunderstorm Experiment (MCTEX) collected by the dual-wavelength Cloud Profiling Radar System (CPRS) show that the CPRS W-band and Ka-band subsystems have nearly equal sensitivity to clouds in a vertically pointing orientation. The Ka-band channel provides useful measurements for horizontal distances of many tens of kilometers even at very shallow elevation angles through convective cores. However, attenuation severely degrades W-band radar sensitivity for elevation angles below approximately 55 degrees.; Since at high altitudes, water vapor turns into ice in cumulonimbus clouds, we also evaluated the ice particles' shape effect; specifically ice bullets and bullet rosettes' shape on the backscattering. This part of the study applies also to cirrus as well as to cumulonimbus clouds. The bullets model was developed using the parameters obtained by airborne measurements from the National Center for Atmospheric Research. A bullet function was created in DDSCAT to compute the individual backscattering coefficient from ice crystals.