Representing 3‐D cloud radiation effects in two‐stream schemes: 1. Longwave considerations and effective cloud edge length
Representing 3‐D cloud radiation effects in two‐stream schemes: 1. Longwave considerations and effective cloud edge length
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表示双流方案中的 3D 云辐射效应： 1. 长波考虑因素和有效云边长度
DOI：
10.1002/2016jd024876
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
B. Mayer
中科院分区：
文献类型：
--
作者：
Sophia Schäfer;R. Hogan;C. Klinger;J. C. Chiu;B. Mayer
现有的天气和气候模式忽略了通过云侧的三维辐射传输，这会显著改变云的辐射效应。这篇由两部分组成的论文描述了通过云面辐射传输的快速算法(Spartacus)的发展，以在全球模式中使用的双流辐射方案中有效地捕捉这些影响。本文讨论的是长波谱区，以前没有做过太多的工作，尽管以前有限的工作表明，通过云侧的辐射传输使浅层积云的长波表面CRE增加了约30%。为了帮助斯巴达克斯的长波能力的发展，我们使用了一个孤立的、等温的、光学厚度的、真空中的立方云的参考案例，对于这种情况，3-D效应恰好使CRE增加了200%。结果表明，对于任何形状的云，只要正确考虑(1)云辐射的有效天顶角，(2)云中通量的空间分布，(3)增强相邻云对辐射的拦截作用的云团，(4)辐射平滑导致有效云边缘长度小于实测值，就可以用Spartacus来表示三维效应。我们的经验发现，椭圆的周长符合水平截面通过积云提供了一个很好的辐射有效云边缘长度的估计，这为如何分析云观测以提取其最重要的辐射属性提供了一些指导。
Current weather and climate models neglect 3‐D radiative transfer through cloud sides, which can change the cloud radiative effect (CRE) significantly. This two‐part paper describes the development of the SPeedy Algorithm for Radiative TrAnsfer through CloUd Sides (SPARTACUS) to capture these effects efficiently in a two‐stream radiation scheme for use in global models. The present paper concerns the longwave spectral region, where not much work has been done previously, although the limited previous work has suggested that radiative transfer through cloud sides increases the longwave surface CRE of shallow cumulus by around 30%. To assist the development of a longwave capability for SPARTACUS, we use a reference case of an isolated, isothermal, optically thick, cubic cloud in vacuum, for which 3‐D effects increase CRE by exactly 200%. It is shown that for any cloud shape, the 3‐D effect can be represented in SPARTACUS provided that correct account is made for (1) the effective zenith angle of diffuse radiation emitted from a cloud, (2) the spatial distribution of fluxes in the cloud, (3) cloud clustering that enhances the interception of emitted radiation by neighboring clouds, and (4) radiative smoothing leading to the effective cloud edge length being less than the measured value. We find empirically that the circumference of an ellipse fitted to a horizontal cross section through a cumulus cloud provides a good estimate of the radiatively effective cloud edge length, which provides some guidance to how cloud observations could be analyzed to extract their most important properties for radiation.
影响因子：
4.9
作者：
J. Shonk;R. Hogan
通讯作者：
J. Shonk;R. Hogan
影响因子：
8.9
作者：
J. Shonk;Robin J. Hogan
通讯作者：
J. Shonk;Robin J. Hogan