The Retrieval of Ice-Cloud Properties from Cloud Radar and Lidar Synergy
The Retrieval of Ice-Cloud Properties from Cloud Radar and Lidar Synergy
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云雷达和激光雷达协同反演冰云特性
DOI：
10.1175/jam2229.1
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
D. Bouniol
中科院分区：
文献类型：
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作者：
C. Tinel;J. Testud;J. Pelon;R. Hogan;A. Protat;J. Delanoë;D. Bouniol
云是地球气候系统的重要组成部分。需要更好地描述它们的微物理性质以改进辐射传递计算。在地球、云、气溶胶和辐射探测器（EarthCARE）使命准备的框架内，由皮埃尔·西蒙拉普拉斯研究所（法国）开发的雷达-激光雷达（RALI）机载系统可用作机载演示器。本文提出了一种新颖的方法，云雷达（94-95 GHz）和激光雷达数据相结合，推导出云的辐射和微物理特性。它结合了雷达的表观后向散射反射率和激光雷达的表观后向散射系数。该算法的原理依赖于消光系数和雷达特定衰减之间的关系的使用，来自机载微物理数据和米氏散射计算。为了求解雷达和激光雷达方程，在云区信号可以从两个仪器，消光系数在某个参考范围z 0必须是已知的。由于算法对于从z 0范围朝向发射器执行的反演是稳定的，所以z 0被选择在由激光雷达观察到的较远的云边界处。然后，假设消光系数与后向散射系数之间的关系，推导出总消光系数、视反射率、云物理参数、有效半径和冰水含量的廓线。该算法适用于盲测试的原始配置文件是来自现场测量的下视仪器。它也适用于真实的激光雷达和雷达数据，获得在1998年云激光雷达和雷达实验（克莱尔'98）现场项目时，原型机载RALI系统飞行指向天底。协同算法的结果与现场测量结果相当吻合。
Clouds are an important component of the earth’s climate system. A better description of their microphysical properties is needed to improve radiative transfer calculations. In the framework of the Earth, Clouds, Aerosols, and Radiation Explorer (EarthCARE) mission preparation, the radar–lidar (RALI) airborne system, developed at L’Institut Pierre Simon Laplace (France), can be used as an airborne demonstrator. This paper presents an original method that combines cloud radar (94–95 GHz) and lidar data to derive the radiative and microphysical properties of clouds. It combines the apparent backscatter reflectivity from the radar and the apparent backscatter coefficient from the lidar. The principle of this algorithm relies on the use of a relationship between the extinction coefficient and the radar specific attenuation, derived from airborne microphysical data and Mie scattering calculations. To solve radar and lidar equations in the cloud region where signals can be obtained from both instruments, the extinction coefficients at some reference range z0 must be known. Because the algorithms are stable for inversion performed from range z0 toward the emitter, z0 is chosen at the farther cloud boundary as observed by the lidar. Then, making an assumption of a relationship between extinction coefficient and backscattering coefficient, the whole extinction coefficient, the apparent reflectivity, cloud physical parameters, the effective radius, and ice water content profiles are derived. This algorithm is applied to a blind test for downward-looking instruments where the original profiles are derived from in situ measurements. It is also applied to real lidar and radar data, obtained during the 1998 Cloud Lidar and Radar Experiment (CLARE’98) field project when a prototype airborne RALI system was flown pointing at nadir. The results from the synergetic algorithm agree reasonably well with the in situ measurements.