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首页> 外文期刊>Journal of Geophysical Research, D. Atmospheres: JGR >A case study of urbanization impact on summer precipitation in the Greater Beijing Metropolitan Area: Urban heat island versus aerosol effects
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A case study of urbanization impact on summer precipitation in the Greater Beijing Metropolitan Area: Urban heat island versus aerosol effects

机译：北京大都市区城市化对夏季降水影响的案例研究：城市热岛与气溶胶效应

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摘要

Convection-resolving ensemble simulations using the WRF-Chem model coupled with a single-layer Urban Canopy Model are conducted to investigate the individual and combined impacts of land use and anthropogenic pollutant emissions from urbanization on a heavy rainfall event in the Greater Beijing Metropolitan Area (GBMA) in China. The simulation with the urbanization effect included generally captures the spatial pattern and temporal variation of the rainfall event. An improvement of precipitation is found in the experiment including aerosol effect on both clouds and radiation. The expanded urban land cover and increased aerosols have an opposite effect on precipitation processes, with the latter playing a more dominant role, leading to suppressed convection and rainfall over the upstream (northwest) area, and enhanced convection and more precipitation in the downstream (southeast) region of the GBMA. In addition, the influence of aerosol indirect effect is found to overwhelm that of direct effect on precipitation in this rainfall event. Increased aerosols lead to more cloud droplets with smaller size, which favor evaporative cooling and reduce updrafts and suppress convection over the upstream (northwest) region in the early stage of the rainfall event. As the rainfall system propagates southeastward, more latent heat is released due to the freezing of larger number of smaller cloud drops that are lofted above the freezing level, which is responsible for the increased updraft strength and convective invigoration over the downstream (southeast) area.
机译：使用WRF-Chem模型与单层城市冠层模型相结合的对流解析整体模拟，研究了大都市区土地使用和人为源于城市化的人为污染物排放对大雨事件的单独影响和综合影响（ GBMA）。包含城市化效应的模拟通常可以捕获降雨事件的空间格局和时间变化。在实验中发现降水有所改善，包括对云和辐射的气溶胶效应。城市土地覆盖面积的扩大和气溶胶的增加对降水过程有相反的影响，后者的作用更为明显，导致上游（西北）地区的对流和降雨受到抑制，下游（东南）的对流和降水增加）GBMA的区域。另外，在这种降雨事件中，发现气溶胶间接作用的影响超过了对降水的直接作用。气溶胶的增加会导致更多的小尺寸云滴，这有利于蒸发冷却并减少上升气流，并在降雨事件的早期抑制上游（西北）区域的对流。随着降雨系统向东南传播，由于冻结在高出冻结水平的大量较小的云滴被冻结，释放出更多的潜热，这导致上升气流强度增加以及下游（东南）区域的对流活跃。

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