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
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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DOI：
10.1002/2015jd023584
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发表时间：
2015-10
期刊：
影响因子：
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通讯作者：
Yali Luo;Yangruixue Chen
中科院分区：
文献类型：
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作者：
Yali Luo;Yangruixue Chen
利用嵌套网格间距为1.11 km的24 h对流允许模式，对2007年7月8日午夜至早晨沿着我国东部梅雨锋的准线性强降水中尺度对流系统（MCS）的预报不确定性和物理机制进行了研究。模拟结果表明，尽管天气环境有利于强降雨的产生，但初始状态对不确定性具有很强的敏感性。一个不太熟练的成员的初始状态的线性变化对一个熟练的成员导致降水模拟的单调改善，最显着的贡献所产生的变化在水分场。对代表次网格尺度过程的物理参数化的敏感性无法解释所检查的物理变化的较大模拟误差（缺少MCS），但可能导致累积降雨量的位置和数量的大范围扩散。合理模拟MCS相关暴雨的最佳性能成员的一个强大功能是在先前对流产生的梅雨锋之前存在冷穹。冷穹通过将西南气流中的高等效位温空气提升到自由对流的水平，促进夜间对流的形成。熟练的成员再现了在这次事件和中国许多其他暴雨事件期间观察到的对流后建和回波带训练过程。相比之下，不太熟练的成员错过了MCS的发展，要么不模拟以前的对流或产生一个冷穹太浅，启动MCS。
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 the MCS‐associated heavy rainfall is the presence of a cold dome ahead of the Meiyu 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.