2014年10月中国东部持续重污染天气成因分析

2014年10月5─13日中国东部发生了大范围、长时间的(雾)霾及重污染天气. 采用AQI数据分析此次大气重污染过程的时、空演变特征,并应用NCEP(美国国家环境预报中心)再分析资料以及地面、小球探空数据,分析了主要天气型演变、边界层及上空的风场、气象条件特征,以研究此次秋季重污染天气的气象成因和形成过程. 结果表明:①华北、东北是此次污染最为严重的地区,其域内各城市持续数日的污染演变可分为AQI显著上升、持续高值、下降3个阶段. ②在AQI上升阶段(10月6—8日),受大陆高压控制,东部地区出现较弱地方风场和偏南风输送风场,风速在0～2 m/s,相对湿度在22%～86%,3 000 m逆温显著利于污染物积累. ③在持续污染阶段(10月8—11日),海上高压滞留,再加上台风“凤凰”北上阻挡大陆高压影响,使东部地区出现持续4 d的偏南风、偏东风弱风场,风速在1～4 m/s,相对湿度为57%～96%,造成严重污染. ④在AQI下降阶段(10月11—12日),后续大陆高压南下,前部冷锋利于污染物清除,风速达到6 m/s,是AQI降低的主要天气背景场. 因此,持续出现的稳定天气形势是导致此次中国东部重污染天气的主要气象原因. 

Analysis of Meteorological Conditions and Formation Mechanisms of Lasting Heavy Air Pollution in Eastern China in October 2014

From October 5-13,4, eastern China experienced a severe air pollution and haze event, which affected unusually sizeable areas and lasted for a long period. In order to better understand the characteristics of the episode and to study its meteorological reasons and formation processes, this paper performs statistical analyses of temporal-spatial distribution of the air pollution using AQI (Air Quality Index) data. The present study employed NCEP (National Centers for Environmental Prediction) reanalysis and meteorological data from the surface and high-balloon stations to analyze the main system patterns, weather conditions and wind fields in the PBL (planetary boundary layer) and the upper air during the episode. The results showed that:1) the North China Plain and the Northeast China Plain were the most polluted areas in this episode. Lasting pollution in each city was the main characteristic of the episode. The time variation of the heavy air pollution process could be divided into three stages, including AQI ascent, lasting pollution and AQI descent. 2) During the AQI ascent stage (October 6-8), the anticyclone in eastern China showed a local and a south weak wind field at the surface and strong temperature inversion at 3000 m, which are favorable for pollution accumulation. The weather conditions provided valuable interpretation for dramatic AQI ascent. 3) During the lasting pollution stage (October 8-11), the stagnation of the anticyclone over the sea and typhoon “Yongfong” gave rise to lasting eastern and southern winds in the East China Plain for four days, which were important factors in the lasting pollution episode. 4) The front of the follow-up anticyclone (October 11-12) was favorable for pollution removal, which was the main system pattern for the AQI descent. In conclusion, the lasting stable system pattern was the main meteorological reason for this episode.