太湖上空大气气溶胶光学厚度及其特征分析

基于高精度的太阳光度计(CE-318)得到太湖上空气溶胶长期观测数据,获得了太湖上空从2005年9月～2010年10月的气溶胶光学厚度(AOT)以及相应的ngstrm参数α.5 a的观测资料表明,太湖上空AOT的高值区出现在夏季的6～7月,低值区出现在秋冬季节的10月～次年1月;α的低值区和高值区分别出现在春季的3～4月和秋季的9～11月,AOT及对应的α的变化主要与该地区的天气形势有关.从频率分布来看,AOT(500 nm)只有一个峰值,最高频率值为0.4～0.6,约占总样本的26%,年均值为0.80.按照平均AOT(500 nm)计算,气溶胶造成的太阳直射辐射的透过率衰减至少为50%,致使太湖地区的大气较为混浊,形成严重的雾霾天气;ngstrm波长指数α有2个峰值,最高频率区间为1.1～1.3和1.3～1.5,分别占总样本的30%,年平均值为1.17.结果还表明AOT(500 nm)和α的日均值变化范围均较大,表明太湖上空有不同类型的气溶胶粒子共存;当α增大时,AOT(500 nm)的均值呈递减趋势.总体结果分析表明,太湖上空的AOT值随时间变化较大,属于城市-工业型气溶胶类型.

Aerosol Optical Thickness of the Atmospheric Aerosol over Taihu Lake and Its Features: Results of In-site Measurements

Based on the data measured in situ by an automatic sun tracking photometer(CE-318),the aerosol optical thickness(AOT) and the corresponding ngstrm coefficient α of the atmospheric aerosol over Taihu Lake from November 2005 to October 2010 were collected.The results showed that high values of AOT over Taihu Lake were measured in summer(June to July) whereas low values were detected in autumn and winter(October to January).However,the low and high values of α appeared in spring(March to April) and in autumn(September to November),respectively.The variations of AOT and α over Taihu Lake may be related to weather patterns in this region.Based on the frequency distribution,AOT(500 nm) had only one peak value,with a maximum frequency of 0.4-0.6 and a yearly average value of 0.80,accounting for 26% of the total sample.Calculated from the mean AOT(500 nm),the solar radiation reduction was reduced by at least 50% by the atmospheric aerosol,resulting in more turbid atmosphere in this region and consequently heavy fog and haze.There were two peak values of the ngstrm coefficient α,with the maximum frequency ranging from 1.1-1.3 and 1.3-1.5 and a yearly average value of 1.17,accounting for 30% of the total sample.Significant variations were also observed in the daily average values of AOT(500 nm) and α,indicating the coexistence of different types of aerosols over Taihu Lake.The mean value of AOT(500 nm) declined when α increased.To sum up,values of AOT(500 nm) over Taihu Lake changed greatly with time,and the aerosol should be classified as an urban-industrial aerosol.