基于星地同步观测的华北平原中部背景地区冬季霾污染过程

摘要

利用地基观测结果和多源卫星遥感观测,结合气象数据及HYSPLIT4后向轨迹模式,对华北平原中部背景地区(河南省郑州市中牟县东南郊)冬季霾事件的污染物特征和形成过程进行分析.综合观测时间为2014年12月13日~2015年1月16日,共有5次霾过程,占观测总天数的82%.地面监测结果显示,不同的污染过程污染物浓度变化曲线相似,O3浓度在清洁天浓度较高；NOx、SO2、PM10、PM2.5呈较强正相关性,NOx、SO2与 PM10相关系数0.64、0.57,与PM2.5相关系数0.56、0.45；近地面污染物以细粒子污染物为主,其中又以气态污染物二次生成的细粒子为主.AMPLE地基激光雷达和CALIPSO数据表明,华北平原霾层中上部受浮尘影响,以粗粒子污染物为主.气象探空数据表明该地区冬季大气对流层稳定利于霾的维持,假相当位温垂直差、K指数、露点差与能见度相关系数分别为0.52、0.56和0.38.分析近地面风速风向对霾过程的影响表明,该地区冬季以南方向静小风为主,风速与能见度相关系数为0.32,PM1受东北方向污染源影响,PM1~2.5及PM2.5~10受西北方向污染源影响；结合高空风场分析,霾过程1受西北浮尘影响,霾过程5受南来水汽影响.通过后向轨迹分析,该地区冬季的低空污染传输主要来自东北和西北方向,其中东北方向区域传输来自河北与山东,占来源比例的14%,近距离污染传输主要来自站点以西的郑州、洛阳,约占来源比例的33%.%This paper employed ground-based measurements, multiple satellite observations, NCEP reanalysis data, meteorological sounding data and Modeled HYSPLIT4backward trajectory results to analyse the pollution characteristics and forming process of haze pollution in Zhongmou, a rural site located in the central North China Plain. The Comprehensive observation campaign lasted from December 13th, 2014 to January 16th, 2015 and a total of five haze pollution episodes were captured Haze days accounted for 82% of the total number of days, while heavily polluted days (Class V and VI based on AQI level) accounted for 46%. The ground-based observations showed that: 1) the concentrations of PM and SO2, NOx were highly correlated, 2) fine particulate matters were dominant among the ground-level pollutants, 3) and the secondary aerosols transformed from gaseous pollutants accounted for a predominant fraction of fine particles. CALIPSO and AMPLE vertical detection data showed that thick haze clouds were dominated by floating dust in the middle and upper layer, and coarse dust particles were prevalent over North China Plain, which accounted for a predominant fraction in the columnar optical volume. Based on meteorological sounding data, the atmospheric stratification of the planetary boundary layer (PBL) was stable, suppressing air turbulence in PBL and favoring formation and maintenance of haze. Meteorological data also showed that near-ground wind speed and direction had a great influence on haze maintenance and dissipation; High-level wind field data indicated that the first haze was influenced by floating dust from the northwest, and the fifth episode was influenced by water vapor from the south. By tracking the 100m air mass using HYSPLIY4model, the low-altitude pollutants were transported from northwest and northeast. The contribution from northeast, accounting for almost 14%, passed Hebei and Shandong province, while short distance transportation traces were mostly from Zhengzhou and Luoyang, accounting for almost 33%.