川南城市群空气质量变化特征及环流影响分析

Analysis of air quality variation characteristics and circulation influence in Southern Sichuan Urban Agglomeration

基于川南城市群空气质量指数(AQI)数据和NECP/NCAR再分析资料,结合年内分配不均匀系数(CV),分析了该地区2020年空气质量变化特征及其与大气环流间的联系。结果表明:1)川南城市群AQI整体呈年内下降趋势,夏、秋季空气质量好于春、冬季;CV轻微上升,表明年内空气质量分配不均匀状态增大,其中冬季空气质量分配差异最大,夏季差异最小,川南西部地区差异大于东部地区。2)受首要污染物PM_(2.5)影响,AQI空间上呈中部高四周低的分布形式,加之PM_(10)的影响,AQI空间分布有明显的季节差异性。春、冬季AQI空间分布特征较为相似,形成中部高值区和北部低值区;夏季分布西高东低,秋季为东南高西北低。3)川南城市群春、冬季处于高空槽后,冷空气的堆积不利于对流发生,污染物排出不畅,使得AQI较高;夏、秋季则由于副热带高压和中高纬低槽的存在易产生对流而发生降水,加之风场辐合形势较明显,污染物不易积聚,因此AQI较低。

Based on the air quality index(AQI)data and NECP/NCAR reanalysis data,combined with the distribution heterogeneity coefficient(CV)within the year,the characteristics of air quality variation and its relationship with atmospheric circulation in Southern Sichuan Urban Agglomeration in 2020 were analyzed.The results showed as follows.1)The AQI value of Southern Sichuan Urban Agglomeration decreased as a whole,the air quality in summer and autumn was better than that in spring and winter;CV rose slightly,and the uneven distribution of air quality within the year increased.Among them,the difference of air quality distribution was the biggest in winter and the smallest in summer,and the regional difference was larger in the west of Southern Sichuan Urban Agglomeration than that in the east.2)Due to the effect of primary pollutant PM_(2.5),the spatial distribution of AQI was high in the middle and low around,and combined with the influence of PM_(10),the spatial distribution of AQI had obvious seasonal differences.The spatial variation characteristics of spring and winter were similar,forming a high value area in the middle and a low value area in the north,high in the west and low in the east in summer and high in the southeast and low in the northwest in autumn.3)When the urban agglomeration in Southern Sichuan Urban Agglomeration was in the upper trough in spring and winter,the accumulation of cold air was not conducive to the occurrence of convection,and the pollutant discharge was not smooth,resulting in the high AQI values in the two seasons.In summer and autumn,due to the existence of subtropical high and low trough in mid-high latitude,it was easy to generate convection and precipitation.In addition,the convergence situation of wind field was obvious,and the pollutants were not easy to accumulate,so the AQI was low.