Impact of Urban Roughness Representation on Regional Hydrometeorology: An Idealized Study
Impact of Urban Roughness Representation on Regional Hydrometeorology: An Idealized Study
复制标题
DOI：
10.1029/2020jd033812
复制
发表时间：
2021-02
期刊：
影响因子：
--
通讯作者：
Qi Li;Jiachuan Yang;Long Yang
中科院分区：
文献类型：
--
作者：
Qi Li;Jiachuan Yang;Long Yang
中尺度气候模式为理解城市地区陆-气相互作用提供了不可或缺的工具。然而，在城市冠层参数（UCPs）和参数化方案的不确定性，导致退化的表现复杂的地形中的阻力效应。特别是，对于广泛应用的单层城市冠层模式（SLUCM）与天气研究和预报（WRF）模式相结合，近地面水平风速被系统地高估。在这项研究中，理想化的大涡模拟（LES）和WRF‐SLUCM模拟进行了研究的UCPs和空气动力参数化的大气边界层过程和降雨变率在亚利桑那州凤凰城的单独影响。对于显式解析地表几何的LES，在地表层及以上发现了城市形态的三维（3D）与二维（2D）表示之间的显着差异。当表面阻力参数化后SLUCM，表面形态的平均动量传递的影响很小。结合3D城市形态数据的WRF‐SLUCM模拟结果表明，简单地改进锋面面积指数将减少表面阻力，这进一步放大了SLUCM在预测水平风速时的系统性正偏差。用基于LES的气动参数代替SLUCM中的阻力参数化对近地面风速有明显的影响。城市粗糙度表示的影响变得最明显，在降雨期间，由于表面阻力的重要作用，在支配水分收敛。我们的研究强调，除了在获得详细的UCP密集的努力，它也是至关重要的，以加强城市动量交换参数化方案。
Mesoscale climate models provide indispensable tools to understand land‐atmosphere interactions over urban regions. However, uncertainties in urban canopy parameters (UCPs) and parameterization schemes lead to degraded representation of the drag effect in complex built terrains. In particular, for the widely applied single‐layer urban canopy model (SLUCM) coupled with the Weather Research and Forecasting (WRF) model, near‐surface horizontal wind speed is known to be overestimated systematically. In this study, idealized large eddy simulations (LES) and WRF‐SLUCM simulations are conducted to study the separate effect of UCPs and aerodynamic parameterization on atmospheric boundary layer processes and rainfall variabilities in Phoenix, Arizona. For LES that explicitly resolves surface geometry, significant differences between three‐dimensional (3D) versus two‐dimensional (2D) representation of urban morphology are found in the surface layer and above. When surface drag is parameterized following SLUCM, surface morphologies have little impacts on the mean momentum transfer. WRF‐SLUCM simulation results, incorporated with 3D urban morphology data, indicate that simply refining the frontal area index will reduce the surface drag, which further amplifies the systematic positive bias of SLUCM in predicting horizontal wind speed. Replacing the drag parameterization in SLUCM by LES‐based aerodynamic parameters has evident impacts on near‐surface wind speed. The impact of urban roughness representation becomes the most evident during rainfall periods, due to the important role of surface drag in dictating moisture convergence. Our study underlines that apart from intensive efforts in obtaining detailed UCPs, it is also critical to enhance the urban momentum exchange parameterization schemes.