上甸子本底站卤代温室气体大气浓度短期波动的个例分析

A case study of short-term fluctuation in atmospheric concentration of halogenated greenhouse gases at Shangdianzi regional background monitoring station

利用轨迹分析法、印痕分析和流场分析法,结合上甸子站卤代温室气体H-1301、HCFC-22、CFC-11和SF6在线浓度观测数据,选取2012年9月7—12日上甸子测站卤代温室气体浓度短期波动典型个例进行分析。轨迹分析结果表明:7日12时,污染发生前,气团主要来自较远的偏西北、偏北方向,水平输送距离长,移动迅速,垂直高度高,对应的卤代温室气体浓度偏低,H-1301、HCFC-22、CFC-11和SF6的体积分数分别为4×10-12、350×10-12、260×10-12、10×10-12;9、10日有一定比例的气团在测站的偏南区域近地面回旋打转,水平输送距离短,垂直高度低,在边界层内缓慢移动,不利于污染物在边界层内扩散,导致卤代温室气体浓度偏高,对测站浓度的短期抬升贡献较大,9日12时H-1301、HCFC-22、CFC-11的峰值体积分数分别达到45×10-12、1 200×10-12、310×10-12,10日03时SF6的峰值体积分数达到28×10-12;11日西南方向回旋气团消失;12日气团完全来自较远的西北方向且轨迹移动较快。印痕分析与轨迹分析结果一致:7、8日敏感性系数较高区域主要分布在测站以北,9、10日敏感性系数较高区域分布在测站偏南,11、12日测站偏南的敏感性系数较高区域消失。流场分析结果表明:9、10日环流形势有利于污染物在测站区域累积,造成测站浓度的短期抬升。

Based on the online observed concentration of H-1301, HCFC-22, CFC-11 and SF6 at Shangdianzi background station during 7--12 September 2012, a typical case about short-term fluctuation of halogenated greenhouse gases is analyzed by means of trajectory, footprint and flow field analysis meth-ods.The trajectory analysis results show that, before occurrence of pollution, air masses mainly come from the further north and northwest at 1200 UTC 7 September 2012, with a long horizontal transport distance, rapid moving speed and high vertical height.Meanwhile ,the corresponding volume fractions of halogenated greenhouse gases are relatively low, which are 4x 10-12, 350x 10-12, 260x 10-12 and 10x 10-12 for H-1301 ,HCFC-22 ,CFC-11 and SF6 ,respectively.However,in 9--10 September 2012 ,a certain per- centage of air masses convolute over the south of the station with a short horizontal transport distance and low vertical height, moving slowly in the boundary layer, which hinders the spread of pollutants in the boundary layer and results in the relatively high concentrations of halogenated greenhouse gases. Such situation contributes a lot to the short-term rapid growth of concentration levels.The peak volume fractions of H-1301 ,HCFC-22 and CFC-11 reach 45x10-12, 1 200x10-12 and 310x10-12 at 1200 UTC 9 September,respectively,and that of SF6 does 28x10-12 at 0300 UTC 10 September.On 11 September, the convoluting air mass in the southwest direction disappears.On 12 September, air masses all come from the far northwest and have rapid moving trajectories.The footprint analysis results are the same as the trajectory analysis results, which are that the regions with high sensitivity coefficient are mainly lo- cated in the north of the station in 7k8 September,and in the south of the station in 9--10 September. Then the regions with high sensitivity coefficients in the south of the station disappear in 11--12 Sep- tember.In addition, the flow field analysis results show that the circulation pattern in 9--10 September is favorable for the accumulation of pollutants in the observed region, resulting in the short-term lift of pollutants＇ concentrations.