北京城市下垫面对雾影响的数值模拟研究

Numerical simulation of the impact of urban underlying surface on fog in Beijing

为了探究北京城市下垫面对雾天气过程的影响,为北京地区雾数值预报水平的提高提供理论基础和科学依据,选取2011年10月29日北京地区雾天个例进行了数值模拟试验,通过对WRF/Noah/UCM模式系统中城市冠层参数的调整,显著改善了模式对此次雾天气过程的模拟效果.使用参数调整后的模式系统通过敏感性试验分析研究了北京城市下垫面对雾发生、发展和消散过程的影响.结果表明:参数调整后的WRF/Noah/UCM模式系统能够与实际观测较相符地模拟此次发生在北京地区的雾天气过程,北京城市下垫面主要通过对温度的改变对雾的形成、发展和消散产生显著影响,使雾不易在城市及其附近形成和发展,延后城市地区雾的形成,但城市的存在也使得城市地区及其附近雾不易消散,相较于没有城市时消散时间延后.

In order to investigate the impact of urban underlying surface on fog in Beijing and improve numerical weather forecast of fog in Beijing, a numerical study of the during 29th and 30th Oct, 2011 above the Beijing area was carried out using WRF/Noah/UCM modeling system. Performances of the model on the fog case were obviously improved through adjusting the parameters in the urban canopy model of the modeling system. Furthermore, the impact of urban underlying surface in Beijing on formation, development and disappearance of fog was studied by model sensitivity tests using the adjusted modeling system. The results show that this modeling system can reconstruct the fog case quite similarly to observation. And formation, development and disappearance of the fog were evidently influenced by urban underlying surface in Beijing. These effects are mainly caused by changes of temperature. Therefore, fog is more difficult to generate.in and near the city and appears much later than non-urban cases. But fog is more difficult and delayed to disappear when the city exists compared to non-urban cases.