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首页> 外文期刊>Journal of Geophysical Research, D. Atmospheres: JGR >Investigation of the predictability and physical mechanisms of an extreme-rainfall-producing mesoscale convective system along the Meiyu front in East China: An ensemble approach
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Investigation of the predictability and physical mechanisms of an extreme-rainfall-producing mesoscale convective system along the Meiyu front in East China: An ensemble approach

机译：中国东部梅雨锋一带产生极端降雨的中尺度对流系统的可预测性和物理机制研究：整体方法

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摘要

Forecast uncertainties and physical mechanisms of a quasi-linear extreme-rain-producing mesoscale convective system (MCS) along the Meiyu front in East China, during the midnight-to-morning hours on 8 July 2007, are studied using ensembles of 24 h convection-permitting simulations with a nested grid spacing of 1.11 km. The simulations reveal a strong sensitivity to uncertainties in the initial state despite the synoptic environment being favorable for heavy rainfall production. Linear changes of a less skillful member's initial state toward that of a skillful member lead to a monotonic improvement in the precipitation simulation, with the most significant contribution arising from changes in the moisture field. Sensitivity to physics parameterizations representing subgrid-scale processes fail to account for the larger simulation errors (missing the MCS) with the physics variation examined but could result in a large spread in the location and amount of accumulative rainfall. A robust feature of the best-performing members that reasonably simulate theMCS-associated heavy rainfall is the presence of a cold dome ahead of theMeiyu front generated by previous convection. The cold dome promotes nocturnal convective initiation by lifting high equivalent potential temperature air in the southwesterly flow to its level of free convection. The skillful members reproduce the convective backbuilding and echo-band training processes that are observed during this event and many other heavy rainfall events over China. In contrast, the less skillful members that miss the development of the MCS either do not simulate the previous convection or produce a cold dome that is too shallow to initiate the MCS.
机译：利用2007年7月8日午夜至早晨，研究了华东梅雨锋准线性极雨产中尺度对流系统（MCS）在24小时对流中的预报不确定性和物理机制。允许的模拟，嵌套网格间距为1.11 km。尽管天气条件有利于大量降雨的产生，但模拟显示出对初始状态不确定性的强烈敏感性。技能水平较低的成员的初始状态相对于技能水平的成员的线性变化导致降水模拟的单调改善，其中最大的贡献来自湿度场的变化。对于代表次网格规模过程的物理参数化的敏感性，无法解释所检查的物理变化所带来的较大的模拟误差（缺少MCS），但可能导致累积降雨的位置和数量发生较大的分布。表现最佳的成员的一个强大功能是，可以合理地模拟与MCS相关的强降雨，这是由先前对流产生的梅雨锋前方存在一个冷穹顶。冷穹顶通过将西南气流中的高等效温度空气提升到其自由对流水平来促进夜间对流启动。熟练的成员再现了这次对流活动以及在中国其他许多强降雨事件中观察到的对流逆流和回声带训练过程。相反，技能欠佳的成员错过了MCS的发展，要么没有模拟先前的对流，要么产生的冷圆顶太浅而无法启动MCS。

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