冷空气过程对江苏持续性霾的影响研究

Study on the impact of cold air on persistent haze from December 14 to 24,2016 in Jiangsu Province,China

利用地面气象观测资料、PM_(2.5)浓度监测资料和数值模式产品对2016年12月14—24日江苏遭遇的一次长时间霾天气过程进行分析.研究结果表明:过程期间有两次冷空气南下影响江苏省,两次冷空气均带来大风和降水,有效地清除了前期污染物,但随后全省PM_(2.5)浓度开始升高.第一次冷空气强度强于第二次,造成的污染也较重.WRF-Chem模式对本次过程的气象场和PM_(2.5)浓度模拟均较好,模拟观测相关系数分别达到0.52~0.99和0.40.模式能够较好地模拟出污染物的输送过程和时空分布.与第二次冷空气过程相比,第一次冷空气过程存在明显的污染物自北向南输送过程,100~500 m高空持续偏北气流(第2次过程为西北-偏西气流),期间全省平均边界层高度(PBLH)只有260 m(低于第2次过程的500 m),不利于污染物垂直扩散,造成地面浓度较高.利用HYSPLIT-4模式追踪了两次过程中淮安、泰州、无锡三站上空100 m处大气48 h后向轨迹,发现第一次过程中污染物来自山东中西部,第二次来自西部内陆地区.

Based on the meteorological,air quality and numerical model data,persistent haze was analyzed from December 14 to 24,2016 in Jiangsu Province,China.The results showed that,there were two cold air processes affected Jiangsu province,together with strong wind and precipitation,which efficiently removed the air pollutants,following with atmospheric pollutants increase.WRF-Chem model can reproduce the meteorological filed and PM（2.5） concentration reasonably（coefficient of correlation r=0.52-0.99 and 0.40,respectively,p=0.005）.The first cold air process was stronger than the second one and led to more severe pollution.The first pollution process had obvious feature of pollution transport process and durative north wind between100 m and 500 m（northwest-west wind in the second process）.The mean PBLH was only 260 m（lower than 500 m in the second process） which limited the air pollution vertical dispersion,and led to the surface high PM（2.5） concentration.HYSPLIT-4 model was used to analyze the 48 h backward trajectories above 100 m during the two processes and suggested that the pollutants came from the mid-west of Shandong in the first process while in the second process they came from the inner land in the west.