Parametrizing the horizontal inhomogeneity of ice water content using CloudSat data products
Parametrizing the horizontal inhomogeneity of ice water content using CloudSat data products
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DOI：
10.1002/qj.1893
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发表时间：
2012-10
影响因子：
8.9
通讯作者：
P. Hill;R. Hogan;J. Manners;J. Petch
中科院分区：
文献类型：
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作者：
P. Hill;R. Hogan;J. Manners;J. Petch
为了在云存在的情况下计算无偏差的微物理量和辐射量，不仅需要知道平均含水量，还需要知道该含水量的分布。本文介绍了基于 CloudSat 数据的云内冰水含量水平不均匀性的研究。特别是，通过关注与大气环流模型 (GCM) 中已有变量的关系，开发了适合包含在 GCM 模拟中的不均匀性参数化。不均匀性以分数标准差 (FSD) 定义，由标准差除以平均值得出。发现冰水含量的 FSD 随着计算的水平尺度以及冰层厚度的增加而增加。与云分数的联系更为复杂；对于小云部分，FSD 随着云部分的增加而增加，而对于阴天场景，FSD 急剧下降。与水平尺度、层厚度和云分数的关系用一个相对简单的方程进行参数化。此参数化的性能在一组独立的 CloudSat 数据上进行了测试。参数化被证明是对单值全局 FSD 假设的显着改进。版权所有 © 2012 英国皇家气象学会和英国皇家版权所有，英国气象局
In order to calculate unbiased microphysical and radiative quantities in the presence of a cloud, it is necessary to know not only the mean water content but also the distribution of this water content. This article describes a study of the in‐cloud horizontal inhomogeneity of ice water content, based on CloudSat data. In particular, by focusing on the relations with variables that are already available in general circulation models (GCMs), a parametrization of inhomogeneity that is suitable for inclusion in GCM simulations is developed. Inhomogeneity is defined in terms of the fractional standard deviation (FSD), which is given by the standard deviation divided by the mean. The FSD of ice water content is found to increase with the horizontal scale over which it is calculated and also with the thickness of the layer. The connection to cloud fraction is more complicated; for small cloud fractions FSD increases as cloud fraction increases while FSD decreases sharply for overcast scenes. The relations to horizontal scale, layer thickness and cloud fraction are parametrized in a relatively simple equation. The performance of this parametrization is tested on an independent set of CloudSat data. The parametrization is shown to be a significant improvement on the assumption of a single‐valued global FSD. Copyright © 2012 Royal Meteorological Society and British Crown Copyright, the Met Office