REMOTE SENSING OF MICROPHYSICAL AND RADIATIVE PROPERTIES OF ICE CLOUDS

本研究的主要目的是开发一种协同观测技术，通过结合地面主动和被动遥感来反演冰云的微物理和辐射特性，并验证其对计划中的星载云雷达和激光雷达从空间测量冰云的有效性。我们发展了有冰云的多云大气的短波(太阳)和长波(红外)辐射的传输计算方案。利用该方案模拟了混合相云和中纬卷层云的观测辐射特性，研究了含冰云的微物理特性与辐射特性之间的关系。一项灵敏度研究表明，可以使用35 GHz和95 GHz双频的云雷达来反演混合相云的微物理特性。此外，我们还得到了三维…的准解析解非均匀大气中的辐射传递方程。初步计算表明，云的均匀分布对辐射场有很大影响，特别是对透射型辐射场的影响；这表明，从透射型太阳辐射测量中遥感云的性质是不可行的。我们开发了一种新的正演算法，利用95 GHz的云雷达和波长为0.532μm的光学激光雷达来反演冰云的有效尺寸和冰水量。该算法使我们能够估计冰云微物理性质的垂直剖面。通过对冰晶取向、尺寸分布形状、对激光雷达信号的多次散射效应以及雷达和激光雷达信号中的观测偏差等潜在误差源的数值模拟，测试了算法的性能。将该算法应用于地面和舰载卷云观测资料，发现冰晶的有效大小与下落速度之间存在密切的相关关系。本研究的结果将有助于改进气候模式中的冰云遥感和云辐射方案。较少

The major purpose of the present study is to develop a synergy observational technique to retrieve microphysical and radiative properties of ice clouds by combining the ground-based active and passive remote sensing, and to validate its effectiveness for the planed satellite-borne cloud radar and lidar for measuring ice clouds from space. We have developed the transfer computation scheme of shortwave (solar) and longwave (infrared) radiation for cloudy atmospheres with ice clouds. By using the computation scheme, we have simulated the observed radiative properties for mixed-phase clouds and mid-latitude cirrostratus clouds and studied the relationship between the microphysical properties and radiative properties of the clouds containing ice particles. A sensitivity study suggested that microphysical properties of mixed-phase clouds can be retrieved by using cloud radars with dual frequencies at 35-GHz and 95-GHz. Further, we have developed a quasi-analytic solution of the three-dimensi … More onal radiative transfer equation for inhomogeneous atmospheres. The preliminary computation showed cloud in homogeneity substantially affects the radiation fields, especially, of the transmitted radiances ; this suggests that remote sensing of cloud properties from the transmitted solar radiance measurements is not-practical.We have developed a new forward algorithm for the retrieval of effective size and ice water content of ice clouds by using a 95-GHz cloud radar collocated with an optical lidar of wavelength at 0.532 μm. The algorithm enables us to estimate vertical profiles of the ice cloud microphysical properties. We have tested the performance of the algorithm through numerical simulations for potential sources of such errors as ice crystal orientation, shapes of size distribution, multiple scattering effects to lidar signals, and observational biases in the radar and lidar signals. We applied the retrieval algorithm to the ground-based and shipboard observation data for cirrus clouds, and found a close correlation between effective size and fall velocity of ice crystals. The results from the present study will be useful for improving ice cloud remote sensing and cloud-radiation schemes in climate models. Less