西安市一次持续重污染过程的清除特征分析

Analysis of Dissipation of a Consecutive Pollution Process in Xi'an

对2019年1月发生在西安市的一次持续重污染过程气象条件进行研究,对污染清除阶段进行对比分析,研究冷锋活动对西安市污染物的输送和清除作用。结果表明:7日白天西风累积风速更大,污染清除速率较快,14日夜间—15日东风累积风速更大,持续半个月的污染状况消除。两次污染清除过程的不同是由冷高压的位置和移动路径不同所造成。关中盆地内的主导风向不同则是风场与地形相互作用的结果。小时加密风场表明污染清除可分为偏西路径和偏东路径。偏东风将汾渭平原的污染物输送至关中盆地,对本地污染状况具有先加重再清除的效果。污染持续期间逆温层维持,上午地面风加强导致近地面污染物浓度降低,午后晴空加热效应明显,贴地逆温减弱或消失,近地层大气垂直混合加强,污染物向上扩散稀释,地面污染物浓度迅速下降。

To study the transportation and removal effects of cold air activities on pollutants in Xi’an,the paper analyzed the meteorological conditions of a continuous heavy pollution process in January 2019 in Xi'an,and made a comparative analysis of the pollution removal stage.The results show that:the pollution removal stage appeared on 7-8 and 14-15 January.The accumulated wind speed of the west wind was greater in the daytime of the 7th,and the pollution removal rate was faster.While the accumulated wind speed of the east wind was greater from the nighttime of the 14th to the 15th,and the continuous pollution was removed.The pollution removal was divided into two stages:the westerly path and the easterly path.The characteristics of the wind field at the weather stations showed that the pollution in Fenwei Plain would be transported to the Guanzhong Basin when the wind speed was relatively low,and the pollution would be aggravated when the front stable stratification was combined.When the cold air moved westward and southward,the east wind in the Guanzhong Basin would be strengthened,and the pollutants would be cleared.The difference of clearing path was the result of the interaction of wind field and terrain,and was closely related to the paths and intensity of cold air.The essence of pollution removal prediction lied in the prediction of wind direction and wind speed on the ground,and the influence of topography should be considered in the Guanzhong basin of Shaanxi province.