The evaporation of frontal and other stratiform precipitation
The evaporation of frontal and other stratiform precipitation
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锋面和其他层状降水的蒸发
DOI：
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发表时间：
1991
期刊：
影响因子：
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通讯作者：
R. A. A. Franks
中科院分区：
文献类型：
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作者：
S. A. Clough;R. A. A. Franks
本文用一维模式考虑了不同类型降水的蒸发。结果表明，雪和结晶冰降水的蒸发发生在较短的时间和更浅的深度比雨，而福尔斯落在两者之间。造成这种差异的主要因素是颗粒的体积密度和终端速度，它们联合收割机使雪的蒸发深度小于雨的十分之一。此外，雪预测的蒸发深度被证明是相当不敏感的详细特性的雪粒子在观察范围内。这种差异的一些影响进行了探讨，通过一个模型描述的相互作用，蒸发降水与环境时，受到大气下降。这个模型最初是由Kamburova和Ludlam（1966）提出的，现在已经扩展到研究可变粒子谱的演化。它表明，降水率的顺序为I-lOmm h -的蒸发的雪是足够的，以维持大气在接近饱和的条件下，尽管下降率的顺序为10- 30厘米s-的，典型的中尺度上观察到的层状环境，如雨带;雨表现出没有可比的行为。这些结果表明，雪的蒸发在锋面和其他层状云中尺度系统的动力学中起着重要的作用。与FRONTS 87实验的下投式探空仪观测结果进行比较，证实了这一观点，该观测结果清楚地表明，在最大降水区域中，中尺度下降增强。
SUMMARY The evaporation of precipitation of differing types is considered by use of one-dimensional models. It is shown that the evaporation of snow and crystalline ice precipitation takes place in shorter times and much shallower depths than for rain, while for graupel it falls between the two. The main factors responsible for the differences in behaviour are bulk density and terminal velocity of particles, which combine to produce evaporation depths for snow less than one tenth those for rain. Further, the evaporation depth predicted for snow is shown to be rather insensitive to detailed characteristics of the snow particles within the observed range. Some of the implications of this difference are explored by means of a model describing the interaction of evaporating precipitation with its environment when subjected to atmospheric descent. The model, originally due to Kamburova and Ludlam (1966), has been extended to study the evolution of a variable particle spectrum. It is shown that for rainfall rates of the order of I-l0mm h -’ the evaporation of snow is sufficient to maintain the atmosphere in a near-saturated condition despite descent rates of the order of 10-30cm s-’, typical of those observed on the mesoscale in stratiform environments like rainbands; rain exhibits no comparable behaviour. These results suggest that the evaporation of snow plays a major role in the dynamics of fronts and other mesoscale systems with stratiform cloud. This view is supported by comparison with dropsonde observations from the FRONTS 87 experiment, which show a clear indication of enhanced mesoscale descent in the region of maximum precipitation.