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 h Pa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。
Based on the monthly average SLP data in the northern hemisphere from 1899 to 2009, East Asian summer monsoon intensity index in recent 111 years was calculated, and the interdecadal and interannual variation characteristics of East Asian summer monsoon were analyzed. The results showed that East Asian summer monsoon in the 1920s was the strongest. The intensity of East Asian summer monsoon after the middle period of the 1980s presented weakened trend. It was the weakest in the early 21st century. Morlet wavelet analysis found that the interdecadal and interannual variations of East Asian summer monsoon had quasi-10-year and quasi-2-year significance periods. The interannual variation of precipitation in the east of China closely related to intensity variation of East Asian summer monsoon. In strong （weak） East Asian summer monsoon year, the rainfall in the middle and low reaches of Yangtze River was less （more） than that in common year, while the rainfall in North China was more （less） than that in common year. The weakening of East Asian summer monsoon was an important reason for that it was rainless （drought） in North China and rainy （flood） in the middle and low reaches of the Yangtze River after the middle period of the 1980s.
