长三角城市群冬季一次重污染天气过程分析

利用NCEP/NCAR和FNL再分析资料，并结合长三角城市群地面气象观测数据，探讨了2014年1月18—25日长三角城市群一次重污染天气过程的气象成因以及污染物路径分析。结果表明，污染期间随着相对湿度和PM2.5浓度的升高，大气能见度明显降低。2014年1月影响我国的东亚冬季风势力偏弱，导致重污染期间冷空气活动偏弱；此外，垂直方向上出现逆温，限制垂直运动的发生、发展。上述因素有利于长三角地区污染物在近地面层堆积，导致重污染天气的发生发展。污染物从温度高的地方向温度低的地方扩散。低空气温低时，不易形成对流，促使污染物在长三角地区堆积。HYSPILT模式模拟显示污染物主要来自山西、河北一带，以平流和弱辐散的方式向长三角地区输送。大气化学模式WRF-Chem可较好地模拟出PM2.5浓度的变化过程，可用作长三角城市群重污染天气预报的业务模式。

Analysis of a Wintertime Heavily Polluted Weather Process in the Yangtze River Delta Urban Agglomeration

By using NCEP/NCAR and FNL reanalysis datasets, and the surface meteorological observations over the Yangtze River Delta urban agglomeration, the physico-meteorological causes and pollutant path for a heavily polluted weather process in the Yangtze River Delta urban agglomeration from January 18 to 25, 2014 were investigated. Results show that the atmospheric visibility decreased significantly with the increase of relative humidity and PM2.5 concentration during the pollution period. East Asian winter winds affecting China were weak in January 2014, resulting in weak cold air activity during the heavy pollution process. In addition, inversion in the vertical direction restricted the development of vertical movement. The above factors were conducive to the accumulation of pollutants near the ground in the Yangtze River Delta region, resulting in the development of heavy pollution. Pollutants diffused from low temperatures to high temperatures. When the air temperature is low, it is not easy to form convection, which makes pollutants accumulate in the Yangtze River Delta region. The HYSPILT model simulation showed that the pollutants mainly came from Shanxi and Hebei, and were transported to the Yangtze River Delta in the form of advection and weak divergence. The atmospheric chemical model WRF-Chem can better simulate the variations of PM2.5 and can be used as an operation model for heavy pollution weather forecast in the Yangtze River Delta urban agglomeration.