香港地区海陆风的显式模拟研究

NUMERICAL EXPERIMENT RESEARCH ON SEA AND LAND BREEZES OVER HONG KONG

利用MM5模式对香港地区的海陆风进行了显式数值研究,模拟的风向、风速和温度与站点的观测值比较一致,较详细地分析了海陆风的日变化规律和三维结构特征,结果显示香港地区海风分布复杂,主要受偏西、偏南和偏东海风气流的影响,形成多个辐合带,海风锋最远可以深入内陆约90 km;陆风较简单,主要是偏北气流,陆风的风速和强度都比海风要弱,与山谷风、城市热岛环流等形成弱的辐合。香港是一个海岸曲折、多丘陵的地区,其中75%的面积是山区,为了研究这些丘陵地形对香港地区海陆风的影响,设计了保留海陆分布,去掉丘陵地形的敏感性试验,结果表明,由于丘陵地形的存在,在白天地形的热力作用是主要的,增强了海风的强度;而晚上动力阻挡作用比较明显,减弱了陆风的强度。

The sea and land breezes over Hong Kong on 28 September 2004 was investigated with mesoscale model MM5. The results of numerical experiment are very consistent with the surface observations, especially wind direction and wind speed. The daily evolution and three dimensional structure of sea and land breezes are simulated. The analysis indicates that the distribution of sea breeze（SB） is complex. Three different SB circulation systems with relatively strong winds are set up, and these SBs create several convergence zones. The maximum distance for the inland penetration of SB front is about 90 km. The land breeze （LB） comes mainly northerly. The wind speed and intensity of LB is lower than SB. The topography in Hong Kong area is characterized by 75 % mountains. To study the effects of topography in Hong Kong area, the sensitivity experiment was designed by reducing topography to flat. It is shown that the dynamic and thermal effects of the topography play an important role in the sea and land breezes circulation.