Urban signatures in the spatial clustering of summer heavy rainfall events over the Beijing metropolitan region
Urban signatures in the spatial clustering of summer heavy rainfall events over the Beijing metropolitan region
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DOI：
10.1002/2013jd020762
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发表时间：
2014-02
期刊：
影响因子：
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通讯作者：
Long Yang;F. Tian;J. Smith;Heping Hu
中科院分区：
文献类型：
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作者：
Long Yang;F. Tian;J. Smith;Heping Hu
利用北京站网和天气研究与预报模式，对2008-2012年北京地区夏季暴雨过程的气候特征进行了分析。观测到两个夏季暴雨事件发生频率较高的“热点”。一个位于城市核心区，另一个位于气候顺风区。设计了两组比较模型运行，以评估有和没有城市存在下的地表特性对模型模拟结果的影响。通过对两套模式的比较，分析和量化了城市化对降水统计量、风暴单体行为和对流相关变量的影响。暴雨强度在城市和下风向区域增加，对应于根据雨量计观测到的两个热点的位置。降水统计量的变化表明，降水的概率分布向较重的上尾分布移动。使用新开发的风暴单体识别程序检查风暴单体的拉格朗日性质。高回波风暴单体倾向于在接近城市时分裂，并在顺风区域合并。城市地区的自由对流水平和行星边界层高度显著增加，最大对流有效位能降低。从气候学的角度来看，城市地表感热通量的增加在模拟降雨的修正中起着主导作用。
The climatology of summer heavy rainfall events over the Beijing metropolitan region during 2008–2012 is investigated with the aid of an observational network of rain gauges and the Weather Research and Forecasting model. Two “hot spots” of higher frequency of summer heavy rainfall events are observed. One is located over the urban core region and the other resides in the climatological downwind region. Two comparative sets of model runs are designed to assess the effect of land surface properties with and without the presence of the city on the model simulation results. By comparing the two sets of model runs, the changes of rainfall statistics, behaviors of storm cells, and variables related to convection due to urbanization are analyzed and quantified. The intensity of heavy rainfall is increased over the urban and downwind region, corresponding to the locations of the two observed hot spots based on rain gauges. The changes of rainfall statistics suggest that the probability distribution of rainfall is shifted toward a heavier upper tail distribution. The Lagrangian properties of storm cells are examined using a newly developed Storm‐Cell Identification procedure. High‐echo storm cells tend to split approaching the city and merge in the downwind region. The level of free convection and the height of the planetary boundary layer are significantly increased over the urban region and maximum convective available potential energy is decreased. Increased sensible heat flux from the urban surfaces plays a dominant role in the modification of simulated rainfall from a climatological perspective.