多云天气下海南岛地形对局地海风环流结构影响的数值模拟

采用WRF中尺度天气预报模式,针对海南岛多云天气条件下的一次典型海风个例,对局地海风环流结构进行数值模拟,分析海风环流的演变特征,并通过设计改变海南岛地形的敏感性试验,探究地形对海南岛局地海风环流结构以及云水分布的影响。结果表明:海岛西部陡峭的山区造成海风强迫抬升,偏南背景风使得海岛北部高空回流明显,海岛西部、北部的海风结构较为完整;地形高度越高,海岛南部山区的阻挡作用越强,西部地区的海风高空回流特征越显著,西部、西北部云水混合比的位置也越深入内陆;受南海季风的影响,与晴空天气相比,多云天气下海风强盛期全岛的最大风速稍大,海风在垂直方向上达到的高度更高;移平地形后,多云天气下全岛风速平均仅减少2~3 m·s^-1,而晴空天气下全岛风速则大大减弱,即多云天气下海风环流水平结构受地形的影响比晴空天气下弱。

Numerical simulation of impact of topography of Hainan Island on structure of local sea breeze circulation under cloudy weather

Based on a typical case of sea breeze under the cloudy weather in Hainan Island,this paper simulates the structure of local sea breeze circulation by using the WRF model(Version 3.7),analyzes the evolution characteristics of sea breeze circulation,and explores the influence of the complex topography on the structures of local sea breeze circulation and the distribution of cloud water by designing the sensitivity experiments with different terrain heights in Hainan Island.Results show that the topography can significantly affect the structure of sea breeze circulation and the distribution of cloud water mixing ratio.The steep mountain area in the western Hainan Island results in the forced lifting of sea breeze.The southerly background wind causes obvious high-altitude back-flow in the northern Hainan Island.A nearly complete structure of sea breeze is revealed in the western and northern Hainan Island.The higher the terrain height is,the stronger the blocking effect of mountain area in the southern Hainan Island is,the more significant the high-altitude back-flow characteristics of sea breeze in the western Hainan Island,and the further the position of cloud water mixing ratio in the western and northwestern Hainan Island is in the inland.Under the influence of the South China Sea monsoon,compared with the clear weather,the maximum wind speed of the whole island is slightly larger in the strong period of sea breeze and the height of sea breeze in the vertical direction is higher under the cloudy weather.After moving the terrain,the average wind speed of the whole island under the cloudy weather only decreases by 2-3 m·s^-1,while under the clear weather,the wind speed of the whole island is greatly weakened,that is to say,the influence of the topography on the horizontal structure of sea breeze circulation under the cloudy weather is weaker than that under the clear weather.