地形辐射效应参数化对海南岛海风环流结构和云水分布模拟的影响

IMPACT OF RADIATION PARAMETERIZATION OF TOPOGRAPHIC EFFECTS ON SEA BREEZE CIRCULATION AND CLOUD WATER PATTERN OVER THE HAINAN ISLAND

采用非静力中尺度模式WRF研究地形辐射效应参数化对海南岛2012年7月5日多云天气条件下的海风环流结构和云水分布模拟的影响,并分析了差异产生的可能原因。地形辐射效应是考虑坡地辐射强迫后,辐射与大气中的各种气体、云以及非均匀下垫面间相互反馈的累积效应。其中地形辐射效应参数化的使用使得温度的模拟更接近实际,对水汽的模拟也有一定改进能力,对风速、风向的改进效果不明显。考虑地形辐射效应后,海风的发生发展演变过程及风场的水平分布无显著变化,但局地海风以及海风对流云的位置和强度有较明显的改变。山区四周的海风环流结构和对流云的变化与坡地辐射强迫直接相关,考虑地形辐射效应后,山坡向阳面的海风有所增强,背阳面的海风减弱;向阳坡谷风减弱,背阳坡谷风增强;同时紧临海岸的山坡对海风的影响与岛上山坡对谷风的作用类似。平坦地区的海风环流和海风对流云总体上有所减弱,其变化原因比较复杂。各向海风的强度变化最终会改变海风辐合线的分布,使海风潜在降水区域发生变化。

Numerical simulation of sea breeze circulation and cloud water pattern and its response to radiation parameterization of topographic effects over the Hainan Island are examined by using the Weather Research and Forecasting（WRF） model. The causes are also analyzed. After using radiation parameterization of topographic effects, the cumulative responses of the interaction among radiation, different kinds of gases, cloud and inhomogeneous underlying surfaces are significant. As a result, it is the radiation parameterization of topographic effects that makes the simulated surface temperature more realistic, which also improves the simulation of humidity. In the case of the wind direction and speed, however, the two simulations differed little. After employing slope irradiance parameterization, the evolution of sea breeze and horizontal distribution of wind changed inconspicuously, but the change of the intensity of local sea breeze and cloud is obvious. Besides, the variation of intensity of sea breeze circulation and cloud water pattern has direct links with slope irradiance. Slope irradiance parameterization has different effects on upslope wind and the sea breeze around the steep mountain may strengthen sea breeze and weaken upslope wind on the sunward side, whereas the opposite is true for the slope away from the sun. So the pattern and intensity of sea breeze change significantly in mountain areas. In addition, sea breeze circulation and cloud in sea breeze fronts in flat areas weaken generally for some complex reasons, and the convergence of sea breeze changes, which is the potential areas of precipitation.