Key Laboratory of Meteorological Disaster of Ministry of Education, Nanjing University of Information Science and Technology, Nanjing 210044, China
本文利用中尺度模式WRF V3.9对2016年8月17日~18日重庆一次城市热岛环流个例进行了数值模拟，探讨了山地城市热岛环流的三维结构和演变特征，分析了热岛环流期间湍流动能和各项湍流通量的特征。结果表明：15：00乡村风开始出现，随着热岛强度增强乡村风增强，18：00热岛环流结构最显著，次日02：00热岛环流结构被破坏，仅低层存在微弱的乡村风。其中，重庆市城市热岛环流最强时，水平尺度约城市尺度的1.5~2倍，垂直厚度约1.3 km，水平风速约2~4 m?s-1，最大上升速度约0.5 m?s-1。受地形、河流以及背景风的影响，环流呈现非对称的结构，且强度较弱。分析湍流特征发现，城市区域的湍流动能明显大于非城市区域，湍流动能的非均匀分布造成城市区域湍流对热量和水汽的输送较非城市区域强。此外，城市热岛环流对湍流水汽通量的影响明显；湍流动量通量补充边界层中因热岛环流发展而造成的动量耗散。
To investigate the structure and evolution characteristics of urban breeze circulation in the mountain city, WRF V3.9 is used to simulate a typical urban breeze circulation case from August 17 to 18, 2016 in Chongqing. In addition, the characteristics of turbulent kinetic energy and turbulent fluxes during this period are also analyzed. The results show that the rural wind begins to appear at 15:00 and increases as the heat island strengthen. The circulation reaches its maximum at 18:00, and is destroyed at 02:00 in the next day. At 18:00, the horizontal scale of the circulation is about 1.5~2 times that of the urban scale, and the vertical scale is about 1.3 km, the horizontal wind speed is about 2~4 m?s-1, the maximum rising speed is about 0.5 m?s-1. Under the influence of topography, rivers and background wind, the circulation is asymmetrical in structure and weak in intensity. Besides, it is found that the turbulent kinetic energy in the urban area is obviously larger than that in the nonurban area, which results in the stronger transport of heat and water vapor by turbulence in the urban area. When it comes to the relationship between turbulent fluxes and urban breeze circulation, it shows that turbulent water vapor flux is affected by urban breeze circulation obviously, turbulent supply momentum for the dissipation caused by urban breeze circulation.