A Bimodal Diagnostic Cloud Fraction Parameterization. Part I: Motivating Analysis and Scheme Description
A Bimodal Diagnostic Cloud Fraction Parameterization. Part I: Motivating Analysis and Scheme Description
复制标题
双峰诊断云分数参数化。
DOI：
10.1175/mwr-d-20-0224.1
复制
发表时间：
2021
影响因子：
3.2
通讯作者：
P. Field
中科院分区：
文献类型：
--
作者：
K. Weverberg;C. Morcrette;I. Boutle;K. Furtado;P. Field
云量参数对地区性、允许对流的数值天气预报是有利的。对于其业务区域中纬度预报，气象局使用了一种诊断云量方案，该方案依赖于单峰、对称的次网格饱和-偏离分布。这一方案以前曾被证明低估了云量，因此基于经验的偏差修正在操作上被用来改善性能。这是两篇系列论文中的第一篇，提出了一种新的诊断云方案，作为操作偏差校正的更基于物理的替代方案。新的云图确定了与强烈逆温相关的夹带。对于位于卷吸带内的模式网格盒，采用湿模式和干模式并置的高斯模来表示次网格条件。由湍流特征推断出的高斯模的平均值和宽度被用来诊断云的含水率和云量。结果表明，对于给定的网格平均湿度，新方案可以诊断出增强的云量，这与目前的操作方法类似。然而，它以一种物理上有意义的方式做到了这一点。利用观测的飞机资料和美国大平原南部的地面反演结果表明，新方案改善了云量、相对湿度和液态水含量之间的关系。该方案的一个新特性是，它能够从大尺度状态中推断出扭曲分布和双峰分布，定性地与观测结果进行比较。第二部分将进行详细的评价和分辨率敏感性研究。
Cloud fraction parameterizations are beneficial to regional, convection-permitting numerical weather prediction. For its operational regional midlatitude forecasts, the Met Office uses a diagnostic cloud fraction scheme that relies on a unimodal, symmetric subgrid saturation-departure distribution. This scheme has been shown before to underestimate cloud cover and hence an empirically based bias correction is used operationally to improve performance. This first of a series of two papers proposes a new diagnostic cloud scheme as a more physically based alternative to the operational bias correction. The new cloud scheme identifies entrainment zones associated with strong temperature inversions. For model grid boxes located in this entrainment zone, collocated moist and dry Gaussian modes are used to represent the subgrid conditions. The mean and width of the Gaussian modes, inferred from the turbulent characteristics, are then used to diagnose cloud water content and cloud fraction. It is shown that the new scheme diagnoses enhanced cloud cover for a given gridbox mean humidity, similar to the current operational approach. It does so, however, in a physically meaningful way. Using observed aircraft data and ground-based retrievals over the southern Great Plains in the United States, it is shown that the new scheme improves the relation between cloud fraction, relative humidity, and liquid water content. An emergent property of the scheme is its ability to infer skewed and bimodal distributions from the large-scale state that qualitatively compare well against observations. A detailed evaluation and resolution sensitivity study will follow in Part II.
影响因子：
3.1
作者：
S. Abel;I. Boutle;K. Waite;S. Fox;P. Brown;R. Cotton;G. Lloyd;Tom Choularton;K. Bower
通讯作者：
S. Abel;I. Boutle;K. Waite;S. Fox;P. Brown;R. Cotton;G. Lloyd;Tom Choularton;K. Bower
在极高分辨率数值天气预报模型中评估山谷冷池和云
影响因子：
5.1
作者：
Hughes J
通讯作者：
Hughes J