Laboratory, Field and Modeling Studies of Raindrop Shape

本研究的目的是通过实验室、野外和模型研究来研究雨滴的自然形状。在实验室中，将使用一个28米长的竖井来评估空气动力反馈在直径为1.5至4.0毫米的落差持续振荡中的作用。还计划使用100米的落柱进行更大的落差试验。此外，我们亦会实地量度不同类型雨滴的振荡频谱和振幅，以研究涡流脱落、雨滴碰撞和湍流对雨滴振荡的促进作用。该项目包括对佛罗里达对流和降水/带电试验(1991年夏季)期间用光学阵列探头测量的雨滴形状的飞机数据进行分析。将通过测量雨量、雨滴大小分布、多普勒雷达反射率和偏振来评估自然雨滴形状的原因。最后，将利用这些观测建立模型，以表征雨中水滴的各种形状。自然雨滴形状的半经验分布将应用于微波散射和偏振问题。

The objective of this research is the investigate of the natural shapes of raindrops through laboratory, field and modeling studies. In the laboratory, a 28-meter shaft will be used to evaluate the role of aerodynamic feedback in the persistent oscillation for 1.5 to 4.0 mm diameter drops. Additional experiments are planned for larger drops using a 100-meter fall column. Also, field measurements of drop oscillation spectra and amplitudes in various types of rain will be conducted to examine the roles of eddy shedding, drop collisions and turbulence in promoting raindrop oscillations. The project includes the analysis of aircraft data of raindrop shape as measured by an optical-array probe during the Convective and Precipitation/Electrification Experiment in Florida (Summer 1991). The causes of natural raindrop shapes will be evaluated using measurements of rain rates, drop-size distributions, Doppler radar reflectivities and polarization. Finally, models will be developed using these observations to characterize the variety of drop shapes in rain. The semi-empirical distributions of natural raindrop shapes will be applied to problems in microwave scattering and polarization.