REMOTE SENSING OF MICROPHYSICAL AND RADIATIVE PROPERTIES OF ICE CLOUDS

点击翻译按钮获取中文摘要

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