2015年10月南京霾污染过程分析

为探讨南京秋季霾污染过程发生的主要影响因素，利用南京信息工程大学太阳光度计观测霾污染发生天气下AOD（aerosol optical depth，气溶胶光学厚度）数据，计算AE_440-1020（?ngstr?m Exponent，波长指数）以及a₂（光谱曲率），结合CALIPSO（Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations）卫星气溶胶组分分析以及MODIS（Moderate Resolution Imaging Spectroradiometer）火点数据，对2015年10月南京霾污染过程进行分析.结果表明:2015年10月出现的两次霾污染过程期间南京地区AE_440-1020均高于1.0并且a₂呈负值，其中10月16日AQI达到峰值（201），AOD₅₀₀达1.51，AE_440-1020达1.37，a₂达-0.77；这两次较为严重的霾污染过程均主要由人为因素（工业污染、城市建设、生物质燃烧、汽车尾气排放等）产生的细粒子所致.后向轨迹分析发现，2015年10月16日南京地区霾污染天气发生的主要原因是区域型污染，同时受长距离输送影响，大量携带人为因素产生的细粒子以及少量沙尘等污染物的空气团途经内蒙古、山东等地到达南京，加剧了当日的污染程度；2015年10月23日南京地区霾污染天气的发生则主要受长距离输送影响，同时也受到区域型污染影响，加剧了当日的污染程度.研究显示，在稳定的气象条件下，较高的相对湿度、较低的地表风速、低混合层高度以及贴地逆温的出现是诱发霾污染天气产生的有利气象条件. 

Analysis of Haze Weather Process in Nanjing City in October 2015

The aim of this study was to investigate the impact of aerosols produced from severe haze process on local meteorology over Nanjing in October 2015. The aerosol optical depth (AOD) observed at Nanjing University of Information Science and Technology (NUIST) from the Sun photometer was used to calculate the Ångström exponent (AE_440-1020) and the spectral curvature (a₂). The AOD₅₀₀ and AE_440-1020 values were observed to be greater than 1.0, while negative values of a₂, indicating dominance of fine-mode aerosols, were found for most of the days, with particularly high values on the heavy haze pollution day (October 16^th). The results showed that extreme values of AQI (201), AOD₅₀₀ (1.51), AE_440-1020 (1.37) and a₂ (-0.77) were found on October 16^th. Furthermore, analysis of aerosol subtypes obtained from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) as well as Moderate Resolution Imaging Spectroradiometer (MODIS) revealed a clear indication of dominance of fine-mode particles resulting from anthropogenic activities such as industrial and construction activities, biomass burning and automobile transportation. The Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model-derived back trajectories on October 16^th revealed that the pollutants were mainly originated from local sources. An exception was long-range transported dust (at higher altitudes) from Inner Mongolia and Shandong provinces, which was responsible for the outbreak of high pollution and column loading. In contrast, the trajectories retrieved on October 23^rd showed clearly that the air masses reaching Nanjing were mainly from long-range transported in addition to the local sources. It was determined that the stagnant synoptic meteorological conditions were characterized by high relative humidity, low wind speed and low mixed layer depth, which likely contributed to increased environmental pollution over the region.