摘要
2018年11月22日12月5日太原市冬季出现一次历时14天的“非典型性”污染过程。通过对该时段污染物浓度监测数据、气象监测数据、环流形势、垂直扩散条件及后向轨迹进行分析,并采用二分K均值算法对后向轨迹聚类。结果发现,此次历时较长的混合型污染过程分为“霾-沙尘-霾-沙尘-霾”五个阶段,整个污染天气过程平均能见度为7.8 km,天气现象肉眼难以分辨。形成此类污染过程的原因是冷空气较弱,近地面大气层结稳定,冷空气对污染物的清除作用有限,同时携带沙尘到达地面,导致霾和沙尘的交替出现。整个污染过程期间的后向轨迹分为4类,以PM_(10)污染为主的沙尘天气影响轨迹(2类轨迹)移动速度(10.5 m/s)高于以PM_(2.5)污染为主的霾天气轨迹移动速度(1、3、4类轨迹,移动速度分别为2.7 m/s、2.9 m/s、7.0 m/s)。从后向轨迹空间特征来看,在垂直方向上出现先下沉再抬升的运动过程,对应首要污染物为PM_(2.5)的霾天气。污染过程期间在霾天气时段,SO_(2)和NO_(2)与PM_(2.5)具有协同变化趋势;在沙尘阶段,随着PM_(10)浓度暴发式增长,上述气态污染物浓度快速下降。
From 22 November to 5 December 2018,an“atypical”pollution process occurred in Taiyuan lasting for 14 days.By analyzing the monitoring data of pollutant concentration,meteorological data,circulation situation,vertical diffusion conditions and backward trajectory,and using the bisecting K-means algorithm,this paper clusters the backward trajectories.The results show that this long-lasting mixed pollution process can be divided into five stages as follows:haze,sand dust,haze,sand dust,and haze.The average visibility during the whole pollution process was 7.8 km,and the weather phenomenon was hard to be distinguished with naked eyes.The main causes responsible for this mixed pollution process are that the cold air was weak,the near-surface atmosphere was stable,the removal effect of cold air on pollutants was limited,and at the same time,the cold air carried dust to the ground,resulting in the alternate occurrence of haze and dust.The tracks during the whole pollution process can be divided into four categories.The movement speed(10.5 m/s)of the trajectory(CAT-2 trajectory)of dust with PM_(10) as the primary pollutant was higher than that of haze with PM_(2.5) as the primary pollutant(CAT-1,3,4 trajectories,at the speed of 2.7 m/s,2.9 m/s and 7.0 m/s respectively).Seeing from the spatial characteristics of backward trajectory,in the vertical movement process,sinking first and then rising appeared corresponding to the haze weather with PM_(2.5) as the primary pollutant.Through the analysis of the concentration change of gaseous pollutants(SO_(2) and NO_(2))during the pollution process,we find that the concentrations of SO_(2) and NO_(2) had a collaborative change trend with PM_(2.5) in haze weather period.In the dust stage,with the explosive growth of PM_(10) concentration,the concentration of the above gaseous pollutants decreased rapidly.
作者
王小兰
闫世明
王雁
郝振荣
郭伟
蒋云盛
贺洁颖
Wang Xiaolan;Yan Shiming;Wang Yan;Hao Zhenrong;Guo Wei;Jiang Yunsheng;He Jieying(Shanxi Institute of Meteorological Sciences,Taiyuan 030002,China;Shanxi Meteorological Information Center,Taiyuan 030006,China)
出处
《气象与环境科学》
2021年第4期43-52,共10页
Meteorological and Environmental Sciences
基金
山西省重点研发计划项目(201803D31220)
山西省自然科学基金项目(201901D111465、201801D221333)
山西省气象局重点项目(SXKZDDW20195605、SXKZDDW20205203)。
