Retrieval of warm cloud optical properties using simple approximations
Retrieval of warm cloud optical properties using simple approximations
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DOI：
10.1016/j.rse.2011.01.010
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发表时间：
2011-06
影响因子：
13.5
通讯作者：
T. Nauss;A. Kokhanovsky
中科院分区：
文献类型：
--
作者：
T. Nauss;A. Kokhanovsky
本文介绍了一种利用光学卫星资料反演白天云光学和微物理参数的新技术--该技术是基于简单而高度精确的近似的渐近解的辐射传输理论已经实施的前向辐射传输模型云。这些近似使得能够在运行时期间求解对应的后向模型的方程，从而导致非常快的计算速度。由于这些渐近解一般只适用于弱吸收介质，预先计算的半无限云的反射函数（以及逃逸函数）的查找表被用来克服这种限制，在这个新的检索。SLALOM能够反演云的光学厚度、有效云滴半径、液体和冰水路径、粒子吸收长度以及水和冰云的一些其他性质。SLALOM与精确的辐射传输计算和NASA的中分辨率成像光谱仪云特性产品的比较显示出非常好的一致性。CLOUD和SLALOM的Fortran实现都可以在http://www.klimatologie.uni-bayreuth.de上根据Creative Commons Attribution-Noncommercial-Share Alike 3.0许可证（参见http：//creativecommons.org/licenses/by-nc-sa/3.0）下载。
A new technique relying on SimpLe Approximations for cLOudy Media (SLALOM) for the retrieval of cloud optical and microphysical parameters from optical satellite data during daytime is introduced. The technique is based on simple yet highly accurate approximations of the asymptotic solutions of the radiative transfer theory which have already been implemented in the forward radiative transfer model CLOUD. These approximations enable a solution of the equations of the corresponding backward model during runtime leading to a very fast computation speed. Since these asymptotic solutions are generally applicable to weakly absorbing media only, pre-calculated look-up tables for the reflection function of a semi-infinite cloud (and also the escape function) are used to overcome this restriction within this new retrieval. SLALOM is capable of retrieving the cloud optical thickness, the effective cloud droplet radius, the liquid and ice water paths, the particle absorption length as well as some other properties of water and ice clouds. The comparison of SLALOM with both exact radiative transfer computations and the NASA MODIS cloud property product shows a very good agreement. A Fortran implementation of both CLOUD and SLALOM is available for download under the Creative Commons Attribution-Noncommercial-Share Alike 3.0 license (see http://creativecommons.org/licenses/by-nc-sa/3.0) at http://www.klimatologie.uni-bayreuth.de.