Simulating Z–LWC Relations in Natural Fogs with Radiative Transfer Calculations for Future Application to a Cloud Radar Profiler
Simulating Z–LWC Relations in Natural Fogs with Radiative Transfer Calculations for Future Application to a Cloud Radar Profiler
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DOI：
10.1007/s00024-011-0332-0
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发表时间：
2012-05
影响因子：
2
通讯作者：
F. Maier;J. Bendix;B. Thies
中科院分区：
文献类型：
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作者：
F. Maier;J. Bendix;B. Thies
天然雾和低层云中液态水含量（LWC）的垂直分布在许多应用中是一个关键变量，例如开发基于卫星的地面雾反演。不幸的是，很少有关于雾LWC配置文件的数据，主要是由于缺乏合适的操作仪器。一种新的地基94 GHz FMCW云雷达可以填补这一空白，如果雷达反射率Z可以转换为LWC通过使用适当的Z-LWC关系。然而，这种关系强烈地依赖于液滴尺寸分布（DSD），几乎不知道自然雾类型。在这项敏感性研究中，在不同类型和生命周期阶段的天然雾的Z-LWC关系的DSD的影响进行了分析，使用辐射传输代码（RTC）和公布的雾滴粒径分布。结果表明，LWC与雷达反射率之间存在直接的非线性关系。Z-LWC方程的比例系数特别揭示了不同生命周期阶段的具体范围。如果在现场对雾的生命周期进行适当的分类是可能的，则结果可以用于适当地将Z转换为LWC。
The vertical distribution of liquid water content (LWC) in natural fog and low stratus is a crucial variable in many applications, e.g. the development of satellite based retrievals of ground fog. Unfortunately, there is very little data concerning fog LWC-profiles, mainly due to the lack of suitable operational instrumentation. A novel ground-based 94 GHz FMCW cloud radar could fill this gap if radar reflectivityZcould be converted to LWC by using appropriateZ–LWC relations. However, this relation strongly depends on drop size distribution (DSD) and is hardly known for natural fog types. In this sensitivity study, the influence of the DSD on theZ–LWC relation in different types and life cycle stages of natural fogs is analyzed using a radiative transfer code (RTC) and published fog drop size distributions. It could be shown that there is a direct but nonlinear relationship between LWC and radar reflectivity. The proportionality factor of theZ–LWC equation in particular reveals specific ranges for the different life cycle stages. If a proper classification of fog life cycle in the field is possible, the results could be used to properly convertZto LWC.