Physics of Clouds and Precipitation

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This project is a continuation of theoretical and observational investigations of certain aspects of cloud and precipitation physics. It comprises the following studies:1. Evaporation of stratiform rain. Numerical calculations of evaporation will be compared with observations by Doppler radar, profiler, radiosondes, and ground-based and airborne measurements of the drop-size distribution. 2. Evolution of drop-size distribution by nucleation, condensation, and coalescence. Special emphasis is on the range of drop sizes where the dominant growth process changes from condensation to coalescence.3. The field of supersaturation in a cloud of growing drops. This will be analyzed by solving the diffusion equation in a medium with a continuously distributed source of vapor and multiple sinks using numerical and approximate analytical methods.4. Microwave attenuation in rain. Simultaneous observations with two radars operating at attenuating wavelengths will be used to estimate the field of attenuation. A theoretical analysis of the Hitschfeld-Bordan approach to attenuation correction will also be carried out.5. Mixing processes in small cumulus clouds. Experimental data on drop-size distributions, water content, temperature, and radar reflectivity will be used to study the small-scale mixing that takes place between cloudy air and the environment.6. The genesis of ice crystal habit. Recent work on the physical principles underlying the genesis of dendritic crystal forms will be studied for possible application to the cloud physical problem of explaining the forms of ice crystals and the dependence of these forms on temperature and humidity.These studies contribute to the fundamental understanding of precipitation development and to applications such as the remote measurement of rainfall by radar.