Characterizing the Radiative Effect of Rain Using a Global Ensemble of Cloud Resolving Simulations
Characterizing the Radiative Effect of Rain Using a Global Ensemble of Cloud Resolving Simulations
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DOI：
10.1029/2018ms001415
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发表时间：
2018-10
影响因子：
6.8
通讯作者：
Peter G. Hill;J. C. Chiu;Richard P. Allan;Jiun-Dar Chern
中科院分区：
文献类型：
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作者：
Peter G. Hill;J. C. Chiu;Richard P. Allan;Jiun-Dar Chern
降雨对辐射通量和加热率的影响是大多数用于天气预报或气候预报的大尺度大气模式忽略的过程。然而，据我们所知，由此产生的辐射偏差的大小仍然无法量化。这项研究的目的是在一系列时间和空间尺度上量化雨辐射效应(RRE)，作为确定这些模型中的辐射方案是否应该包括雨的一步。利用一组云分辨模式模拟的输入进行离线辐射传输计算，发现降水对全球平均辐射通量的影响可以忽略不计(小于0.2Wm−2)。特定位置的周平均RRE可能更大(小于4W m−2)。在最好的时间和空间分辨率下，RRE有时会再次大得多(大于100W m−2)，但超过10W m−2的情况发生在不到0.1%的情况下。通过对个例研究的详细分析，我们证明了RRE的大小和方向取决于雨水路径、它相对于云的垂直位置，以及对于长波辐射，它发生的温度。较大的RREs一般只在雨水路径较大而云水路径较小时才出现。这些病例很少见，而且是间歇性的。由于RRE通常很小，我们得出结论，这种缺失的过程对大尺度大气模式不太可能是重要的。
The effect of rain on radiative fluxes and heating rates is a process that is neglected in most of the large scale atmospheric models used for weather forecasting or climate prediction. Yet to our knowledge, the magnitude of the resulting radiative bias remains unquantified. This study aims to quantify the rain radiative effect (RRE) at a range of temporal and spatial scales, as a step toward determining whether the radiation schemes in these models should include rain. Using off‐line radiative transfer calculations with input from an ensemble of cloud resolving model simulations, we find that rain has a negligible effect on global mean radiative fluxes (less than 0.2 W m−2). Weekly mean RREs at specific locations may be larger (less than 4 W m−2). At the finest temporal and spatial resolutions, the RRE can occasionally be much larger again (greater than 100 W m−2), but values exceeding 10 W m−2 occur in less than 0.1% of cases. Using detailed analysis of case studies we demonstrate that the magnitude and direction of the RRE depend on the rain water path, its vertical location with respect to cloud, and, for longwave radiation, the temperature at which it occurs. Large RREs generally only occur when the rain water path is large and the cloud water path is small. These cases are infrequent and intermittent. As the RREs are generally small, we conclude that this missing process is unlikely to be important for large scale atmospheric models.