沈阳一次严重污染天气过程持续和增强气象条件分析

2015年11月7-9日沈阳出现罕见的持续严重污染天气，采用环流形势、地面常规气象观测、污染物浓度观测、风廓线雷达及雨滴谱资料等，对此次污染成因进行了研究.结果表明:在此次严重污染天气过程中，连续22 h AQI≥500，首要污染物均为PM_2.5，其异常峰值最高达到1308μg/m3；ρ（PM_2.5）与ρ（PM₁₀）、ρ（NO₂）和ρ（CO）的相关系数分别达到0.996、0.602、0.891，并且ρ（PM_2.5）与ρ（PM₁₀）、ρ（CO）的正相关性更为显著；在污染的同时出现了降水，11月7和8日的日降水量分别为9.9和2.3 mm，但降水对污染物的稀释和清除作用并不明显.稳定的大尺度环流和对流层内中低层大气层结持续稳定、连续4个时次的探空曲线显示925~850 hPa之间存在多个逆温层（逆温强度最大可达5℃）、相对湿度较大（日均相对湿度在75%以上），是此次严重污染天气持续的有利气象条件.风廓线雷达探测的整层大气垂直速度很小，多介于-1~1 m/s之间，并且近地面2 m/s以下弱下沉的垂直速度为严重污染天气过程提供了较好的动力条件.此外，近地面风力可达3~4级，有利于上游污染物的水平输送.研究显示，此次严重污染天气过程还与外围秸秆集中燃烧所导致的大量污染物长距离输送有密切关联. 

Analysis of Persistence and Intensification Mechanism of a Heavy Haze Event in Shenyang

A heavy continuous haze event that occurred from November 7 th to 9 th, 2015, in Shenyang area was comprehensively analyzed based on the environmental data including circulation pattern, meteorological observation data, pollutant concentrations, wind profiler and raindrop information.The results show that the AQI was more than 500 for 22 hours.PM_2.5 was the primary pollutant, with the highest concentration reaching 1308 μg/m3.The coefficient variables between PM_2.5 and PM₁₀, NO₂ and CO were 0.996, 0.602 and 0.891 respectively.The positive correlation of PM_2.5 with PM₁₀ and CO was significant.The daily precipitation on November 7th and 8th were, respectively, 9.9 mm and 2.3 mm, but the dilution and scavenging effects of precipitation were not obvious for pollutants in this haze event.Stable large-scale circulation and atmospheric stratification occurred in the middle and lower troposphere, while various inversion layers between 925 hPa and 850 hPa, displayed by four consecutive hours sounding curve(the maximum intensity of inversion could reach 5℃) and high relative humidity(the mean daily relative humidity was more than 75%), were the advantageous meteorological conditions.The vertical velocities of the whole atmospheric layer according to wind profiler radar were between -1 to 1 m/s, which were very slow.Weak vertical velocity below 2 m/s near the ground provided excellent dynamic conditions during this heavy haze event.Near surface wind could reach level 3 to 4, which was advantageous to the transportation of the upstream pollutants.The long distance transport of large amounts of pollutants caused by the burning of straws in Shenyang's periphery was probably related to this haze event.