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基于城市冠层方案和局地气候分区的成都市城市夏季气象场模拟

Simulation of Urban Summer Meteorological Field in Chengdu City Based on Urban Canopy Models and Local Climate Zones

  • 摘要: 基于中尺度气象模式WRF,分别使用2021年成都市局地气候分区(Local Climate Zones, LCZs)下垫面和由MODIS数据生成的传统下垫面,结合单层城市冠层方案(Urban Canopy Model, UCM)及多层城市冠层方案(Building Environment Parameterization, BEP),通过4种组合方案对成都城市夏季气象场进行模拟,利用不同城市LCZ下垫面类型的气象测站资料评估模拟结果。研究发现:温度对于下垫面改变更加敏感,风速对城市冠层方案改变响应更强。采用LCZ下垫面和BEP方案结合的案例在城市的气温和风速日变化上更接近实测,能更好模拟出成都主城区向外温度降低、风速增大的空间分布;BEP方案对于城市冠层的较好描述使其改善了UCM方案模拟的夜间温度偏高、风速偏大的问题,能更准确地预测温度和风速的变化;LCZ下垫面对紧凑低层、开敞中层、开敞低层气温模拟结果有显著优化,且改善了传统下垫面模拟风速偏大的结果,特别是在建筑分布紧凑的地区。这表明LCZ分类对传统下垫面城市划分的空缺有较好补充,并能精确刻画建筑形态特征,增大城市冠层内的粗糙度。LCZ分类的城市下垫面结合WRF中多层城市冠层模式BEP可以明显提高成都市城市夏季气象场的模拟精度,可以为城市气候预测及空气质量预报提供有效技术支撑。

     

    Abstract: This study leverages the WRF mesoscale meteorological model to simulate summer urban meteorological conditions in Chengdu, using four different combinations of land surface types and urban canopy schemes. Specifically, it incorporates 2021 Chengdu Local Climate Zone (LCZ) land cover data and traditional MODIS land cover data alongside a single-layer Urban Canopy Model (UCM) and multilayer Building Environment Parameterization (BEP). The simulations are evaluated using meteorological station data across various LCZ surface types. Key findings reveal that temperature is more sensitive to changes in land cover data, while wind speed is particularly responsive to alterations in urban canopy schemes. The combination of LCZ surface data and the BEP model closely aligns with observed diurnal variations in urban temperature and wind speed, accurately capturing the spatial distribution of decreasing temperature and increasing wind speed from Chengdu’s urban core to its outskirts. The BEP model’s detailed representation of the urban canopy significantly improves upon the UCM model, particularly in correcting the overestimation of nighttime temperatures and wind speeds, leading to more accurate predictions. Moreover, LCZ surface data substantially enhances temperature simulations in compact low-rise, open mid-rise, and open low-rise areas and reduces overestimated wind speeds found with traditional land surface data, especially in densely built-up areas. These results suggest that the LCZ classification effectively complements traditional urban land surface categorizations by offering detailed building morphology and enhanced surface roughness within the urban canopy. Incorporating LCZ-based surface data with the BEP model in WRF markedly enhances the accuracy of Chengdu’s summer meteorological simulations, offering valuable technical support for urban climate forecasting and air quality prediction.

     

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