Impacts of Urban Canopy on Two Convective Storms With Contrasting Synoptic Conditions Over Nanjing, China
Impacts of Urban Canopy on Two Convective Storms With Contrasting Synoptic Conditions Over Nanjing, China
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DOI：
10.1029/2020jd034509
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发表时间：
2021-04
期刊：
影响因子：
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通讯作者：
Long Yang;Qi Li;Huiling Yuan;Z. Niu;Lachun Wang
中科院分区：
文献类型：
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作者：
Long Yang;Qi Li;Huiling Yuan;Z. Niu;Lachun Wang
城市引起的降雨异常多种多样，凸显了加强对城市极端降雨的了解的必要性。在这项研究中，我们研究了中国南京降雨量的城市变化。我们的结果基于每小时降雨观测的气候学分析以及高分辨率天气研究和预报模型模拟以及不同的城市物理方案。开发了城市冠层参数（UCP）的网格数据集，以更好地表征南京市中心的几何特征。对两场对流风暴进行了研究，以揭示城市冠层对具有对比天气条件的风暴的时空降雨变化的影响。我们表明，模型模拟与多层城市物理方案和网格 UCP 相结合可以显着减少地表热场和动力场的偏差，但其在降雨模式中的表现随风暴事件而变化。城乡交界处存在由建筑群引起的强辐合带，导致强天气条件下的风暴对流增强，而弱天气条件下的风暴水汽通量分叉。风暴要素的拉格朗日分析进一步说明了城市冠层在弱天气条件下使风暴单元偏转接近城市的作用。城市冠层引起的正降雨异常量级范围为风暴总降雨量的 60% 至 100%。我们的研究强调了在研究城市对流降雨时改进城市冠层特征和扰动大气边界层过程的必要性。
Diverse urban‐induced rainfall anomalies highlight the need for improved understanding on extreme rainfall in cities. In this study, we examine urban modification of rainfall over Nanjing, China. Our results are based on climatological analyses of hourly rainfall observations and high‐resolution Weather Research and Forecasting model simulations coupled with different urban physics schemes. A gridded dataset of urban canopy parameters (UCPs) was developed to better characterize the geometrical features of downtown Nanjing. Two convective storms were investigated to shed light on the impacts of urban canopy on spatial and temporal rainfall variabilities for storms with contrasting synoptic conditions. We show that the model simulations coupled with the multi‐layer urban physics scheme and the gridded UCPs can noticeably reduce biases in surface thermal and dynamic fields, but its performance in rainfall patterns varies with storm events. There is a strong convergence zone over the urban‐rural interface induced by building complexes, leading to intensified convection for the storm with strong synoptic conditions but bifurcated moisture fluxes for the storm with weak synoptic conditions. Lagrangian analysis of storm elements further illustrates the role of urban canopy in deflecting storm cells approaching the city for the storm under weak synoptic conditions. The magnitudes of positive rainfall anomalies induced by urban canopy range from 60% to 100% of the storm‐total rainfall. Our study highlights the necessity of improved characterization of urban canopy and the perturbed atmospheric boundary layer processes in examining urban convective rainfall.