Abstract-Single scattering properties of ice crystals are described at microwave frequencies using discrete dipole approximations and Rayleigh scattering techniques. For a given shape, the average bulk densities of ice crystals can be estimated using the ratio of the copolarized radar signal in a linear (horizontal, vertical) polarization basis. Reflectivity depends on the ice content (g . m-3 ) , and also on both size distribution parameters and average bulk density of the scatterers. Differential propagation phase is primarily a function of shape, ice water content, and is independent of size distribution parameters. Thus, by using a combination of polarimetric radar measurements, average ice content, bulk density, and shape of distributed scatterers can be inferred. These techniques become quite complex in the case of a winter storm where scatterers can exist with varying shape and bulk densities. Polarimetric radar properties of such complex distributed scatterers are modeled. Physical variations in the relation among ice water content, reflectivity, and differential propagation phase are considered with respect to change in the shape of size distribution, bulk density, and average shape of the scatterers. Also, simultaneous polarimetric radar observations and in situ aircraft measurements are shown to demonstrate practical applicability of the techniques.

Short-period (1-5 min) temperature and humidity soundings up to 10-km height are retrieved from ground-based 12-channel microwave radiometer profiler (MWRP) observations. In contrast to radiosondes, the radiometric retrievals provide very high temporal resolution (1 min or less) of thermodynamic profiles, but the vertical resolution, which declines in proportion to the height above ground level, is lower. The high temporal resolution is able to resolve detailed meso-g-scale thermodynamic and limited microphysical features of various rapidly changing mesoscale and/or hazardous weather phenomena. To illustrate the MWRP capabilities and potential benefits to research and operational activities, the authors present example radiometric retrievals from a variety of dynamic weather phenomena including upslope supercooled fog, snowfall, a complex cold front, a nocturnal bore, and a squall line accompanied by a wake low and other rapid variations in low-level water vapor and temperature.

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