Physics of Clouds and Precipitation

这个项目是对云和降水物理某些方面的理论和观测研究的继续。主要包括以下几个方面的研究：1.层状雨蒸发。蒸发的数值计算将与多普勒雷达、剖面仪、无线电探空仪以及地面和空中测量的液滴大小分布的观测结果进行比较。2.成核、凝聚和合并过程中液滴大小分布的演化。特别强调了液滴尺寸的范围，在该范围内，主要的生长过程从凝聚转变为聚结。水滴不断增长的云中的过饱和场。这将通过求解具有连续分布的水汽源和多个汇的介质中的扩散方程来进行分析，使用数值和近似分析方法。微波在雨中的衰减。将使用两个工作在衰减波长的雷达的同时观测来估计衰减场。还将对希希菲尔德-博尔丹衰减校正方法进行理论分析。小积云中的混合过程。有关水滴大小分布、水分、温度和雷达反射率的实验数据将被用来研究云层空气与环境之间发生的小尺度混合。冰晶习惯的起源。最近关于树枝状结晶形成的物理原理的研究将被用于解释冰晶的形式以及这些形式与温度和湿度的关系的云物理问题上。这些研究有助于对降水发展的基本理解和应用，如雷达遥测降雨量。

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.