摘要
通过分析2008年6月至2009年5月期间浦东新区灰霾天气出现的特征,并以2008年12月19日至2008年12月21日一次典型的灰霾天气过程为例,利用激光雷达(Light laser detection and ranging,简称Lidar)数据资料反演得到气溶胶消光系数及其强度图和廓线图,结合地面气象数据和气溶胶观测资料,分析了此次灰霾天气形成的原因.一年的观测资料表明,上海地区冬季和春季易产生灰霾天气,冬季出现重度霾最多,秋季和夏季灰霾天气较少.较弱的太阳辐射以及静风、小风是导致灰霾天气发生的重要原因,且高湿度的霾天气对能见度影响更大.大气边界层(以下简称边界层)高度变化决定着灰霾天气发生的强度,当边界层高度在1km左右时,易发生轻微霾天气,当边界层高度降至600m左右时,易发生中度、重度霾天气,而太阳辐射强度变化决定着边界层高度的变化.轻微霾天气下,大气气溶胶垂直分布最强消光值约为0.15km-1,而重霾天气下可达0.30km-1以上.本次霾过程还受地面颗粒物排放的影响,主要是PM1和PM2.5,且在消光作用中散射性气溶胶的贡献大于吸收性气溶胶.轻微霾天气下PM2.5浓度为50μg·m-3,黑碳浓度为5000ng·m-3,浊度为200Mm-1,而重度霾时则分别达到200μg·m-3、24000ng·m-3和1400Mm-1.随着此次霾的出现,整层大气气溶胶光学厚度(AOD,550nm)不断增加,在重度霾时达到0.6左右,Angstrom指数在重度霾时显著降低,表明有大颗粒物导入,说明此次重度霾天气的发生还与气溶胶的输送有关.
A haze event in Shanghai between December 19 and 21 in 2008 is analyzed in this study. The haze data （ including aerosol extinction and vertical profile） was measured by a Micro-Pulse Lidar in Pudong,Shanghai. In order to evaluate the Lidar aerosol measurement,the surface aerosol measurement at the same site is compared with the Lidar result. The analysis of haze occurrences from a long term measurement （ between June,2008 and May,2009） suggests that the highest occurrences of haze events were in winter and spring,and the most severe haze events occurred in winter. The haze occurrences were fewer in fall and summer than in winter and spring. The analysis shows that the severe haze events often occurred under clam wind and weak radiation conditions in Shanghai. The humidity has important impact on visibility during the severe haze events. The altitude variation of the Planetary Boundary Layer（ PBL） decide the haze intensity. The Planetary Boundary Layer （ PBL） was 1000 meters in the median haze event and 600 meters in the severe haze events. During the median and severe haze days,the aerosol extinction coefficients were about 0. 15 and 0. 30 km -1, respectively. The emission of the particles（ PM1 and PM2.5） also affect the haze event,and the contribution from the scattering aerosol are more than from the absorbing aerosol in extinction. In mild haze days,the concentrations of PM2.5 and BC were about 50 and 5 μg·m -3,respectively,with an extinction coefficient of 200 Mm -1. By contrast,in severe haze days,the concentrations of PM2.5 and BC reached about 200 and 24μg·m -3,respectively,with an extinction coefficient of 1400 Mm -1. The aerosol optical depth （ AOD） at 550 nm in the severe haze event was high with a maximum value of 0. 6. At the same time,a decrease in Angstrom index suggested that the concentrations of large particles were high and the long range transportation of aerosols played an important role in the severe event.
出处
《环境科学学报》
CAS
CSCD
北大核心
2010年第11期2164-2173,共10页
Acta Scientiae Circumstantiae
基金
国家自然科学基金(No40975012)
国家重点基础研究发展计划(973)(No2006CB403700
2011CB403405)~~
关键词
灰霾
气溶胶
激光雷达
消光系数
haze
aerosol
micro-pulse Lidar
extinction coefficient
