Besides local sources of pollution,the outside pollutants transport is one of the most important factors significantly affecting air pollution. Lagrangian mixed with single particle trajectory model ( HYSPLIT) was used to investigate the characteristics of air transport channels during severe pollution events in He′nan province. Mete-orological background fields were also analyzed using the surface wind field and NCEP reanalysis data. The results indicate that the northwest airflow is prevalent in winter over He′nan province during 1986 and 2015 . The air mas-ses mainly come from Eurasia, passing Hebei, Shaanxi and Shanxi provinces, finally reaching He′nan province. Statistics of the 17 severe pollution events in 2015 shows that the air transport channels are mainly from the south (32%),the north (24%) and the east (27%) direction,respectively,which are generally below 900 hPa. After severe pollution event,the northwest wind becomes stronger whereas the south wind disappears,then the pollutants spread promptly. The simulation on severe pollution events occurring during December 5-13,2015 suggests al-though it doesn′t account for the highest proportion,the northern channel brings most pollutants while passing the higher-pollutant areas. The weaker wind against diffusion in this channel contributes to pollution as well. Meteoro-logical observations further confirm that static stability situations control He′nan province while severe pollution occurs. Much vapor is brought by the southeast wind,and high relative humidity doesn′t favor diffusion.%大气污染除了受本地污染源的影响外,外来污染物的输送也是重要的影响因子之一.本文基于拉格朗日混合单粒子轨迹模型(HYSPLIT)分析了河南省重污染过程空气输送通道的特征,并结合地面风场观测资料和NCEP再分析资料对污染发生时的气象背景场进行了探讨.结果表明:在1986-2015年冬季气候平均态下,河南省盛行西北气流,空气输送主要来自西北欧亚大陆,经河北、陕西和山西等地区进入河南地区.2015年河南省17次重污染过程主要空气污染输送分别来自南方(32%)、偏北方(24%)和偏东方(27%),3条通道在输送过程中高度基本维持在900 hPa以下;重污染过后西北风加强,南风消失,污染物迅速扩散.由2015年12月5-13日河南地区重污染过程的模拟表明,偏北空气输送通道所占比例虽然不是最高的,但经过污染物浓度高值区携带的污染物较多,同时由于风速减弱,不利于污染物扩散.气象观测资料进一步证明河南省重污染过程发生时处于静稳天气状态,同时东南风带来了较多的水汽输送,相对湿度偏高不利于污染扩散.
展开▼
