Mixed‐phase clouds in a turbulent environment. Part 2: Analytic treatment
Mixed‐phase clouds in a turbulent environment. Part 2: Analytic treatment
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湍流环境中的混合相云第 2 部分：分析处理。
DOI：
10.1002/qj.2175
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发表时间：
2014
影响因子：
8.9
通讯作者：
Alexei Korolev
中科院分区：
文献类型：
--
作者：
P. Field;A. Hill;K. Furtado;Alexei Korolev
过冷水和冰的共存从热力学角度来说是不稳定的。当没有外力作用时，冰会以过冷液态水为代价而增长，最终将其完全去除。当施加动力强迫时，在有冰存在的情况下有可能激活过冷液态水。文中给出了解析解，用于估算在受湍流影响的已有冰云中可发现的过冷液态水的比例和数量。所采用的方法是将表示过饱和度演变的方程简化为一个随机微分方程。该方程的解给出了相对于冰的过饱和度方差的表达式，它是描述湍流和冰云的参数的函数。给定相对于冰的过饱和度分布，就可以预测混合相云的特性，包括混合相云的比例、平均液态水含量和液态水分布。在湍流环境中对混合相云进行十米分辨率模拟得到的大涡模拟结果与解析估算结果吻合良好。
The coexistence of supercooled liquid and ice is thermodynamically unstable. When no external forcing is applied, the ice will grow at the expense of the supercooled liquid water, eventually removing it completely. When dynamical forcing is applied, it is possible to activate supercooled liquid water in the presence of ice. Analytic solutions are presented that provide an estimate of the fraction and amount of supercooled liquid water that can be found in pre‐existing ice cloud affected by turbulence. The approach used is to simplify the equation representing the evolution of supersaturation to a stochastic differential equation. The solution to this equation provides an expression for the variance of the supersaturation with respect to ice as a function of the parameters describing the turbulence and the ice cloud. Given a supersaturation distribution with respect to ice, the mixed‐phase cloud properties can be predicted, including mixed‐phase cloud fraction, mean liquid water content and liquid water distribution. Large Eddy Simulation results from decametre‐resolution simulations of mixed‐phase cloud in a turbulent environment are in favourable agreement with the analytic estimates.