On the application of the classic Kessler and Berry schemes in Large Eddy Simulation models with a particular emphasis on cloud autoconversion, the onset time of precipitation and droplet evaporation
On the application of the classic Kessler and Berry schemes in Large Eddy Simulation models with a particular emphasis on cloud autoconversion, the onset time of precipitation and droplet evaporation
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经典Kessler和Berry方案在大涡模拟模型中的应用，特别强调云自动转换、降水开始时间和液滴蒸发
DOI：
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发表时间：
1998
期刊：
影响因子：
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通讯作者：
P. Jonas
中科院分区：
文献类型：
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作者：
S. Ghosh;P. Jonas
许多大涡模拟（LES）模式使用经典的Kessler参数化，无论是因为它是或在一个修改的形式来模拟云水自动转换成降水的过程。Kessler方案是线性的，特别有用，并且在计算上易于实现。然而，该方案的一个主要局限性在于它无法预测海洋和大陆云的不同自动转换率。相反，Berry公式克服了这个困难，尽管它是立方的。由于它们的不同形式，很难将这两种解决方案相互匹配。在本文中，我们挑选出的云转换和吸积的过程中运行在一个深模式云和忽略平流项为简单。这有利于精确的分析积分，我们能够推导出新的表达式的降水发病时间使用凯斯勒和贝瑞配方。然后讨论了两种格式等价的条件。最后，我们还严格审查的过程中的经典凯斯勒计划的框架内的液滴蒸发。我们改进了现有的参数化与水蒸气的扩散质量输送的准确估计。然后，我们通过将我们的结果与Beard和Pruppacher的实验观察结果进行比较，证明了我们的计算的整体稳健性，并找到了很好的一致性。
Many Large Eddy Simulation (LES) models use the classic Kessler parameterisation either as it is or in a modified form to model the process of cloud water autoconversion into precipitation. The Kessler scheme, being linear, is particularly useful and is computationally straightforward to implement. However, a major limitation with this scheme lies in its inability to predict different autoconversion rates for maritime and continental clouds. In contrast, the Berry formulation overcomes this difficulty, although it is cubic. Due to their different forms, it is difficult to match the two solutions to each other. In this paper we single out the processes of cloud conversion and accretion operating in a deep model cloud and neglect the advection terms for simplicity. This facilitates exact analytical integration and we are able to derive new expressions for the time of onset of precipitation using both the Kessler and Berry formulations. We then discuss the conditions when the two schemes are equivalent. Finally, we also critically examine the process of droplet evaporation within the framework of the classic Kessler scheme. We improve the existing parameterisation with an accurate estimation of the diffusional mass transport of water vapour. We then demonstrate the overall robustness of our calculations by comparing our results with the experimental observations of Beard and Pruppacher, and find excellent agreement.