新疆地区不同下垫面气溶胶光学特性的分析

Analysis of aerosol optical properties on different underlying surfaces in Xinjiang

利用太阳光度计CE318资料,对新疆地区3个观测站点(阿克达拉、乌鲁木齐、塔中)所代表的草场、城市和沙漠下垫面的440 nm波长处气溶胶光学厚度(AOD)和440~870 nm之间的Angstrom波长指数(AE)进行了统计分析,结果表明:三个站点的AOD年均值塔中站最大、乌鲁木齐站次之、阿克达拉站最小。其中阿克达拉站点的AOD全年变化不大,其月均值均小于0.3;乌鲁木齐站点AOD则表现出明显的季节性变化,冬春季的AOD月均值是夏秋季节的2.17倍;塔中站全年的AOD表现为单峰型,大值时段主要集中在3-7月。三个站点的AE年均值阿克达拉站最大、乌鲁木齐站次之、塔中站最小。阿克达拉和乌鲁木齐站点的AOD以人为排放等小粒径气溶胶为主,塔中站的AOD主要为沙尘等大粒径气溶胶。从年际变化来看,乌鲁木齐站AOD总体呈下降趋势,塔中站和阿克达拉站AOD总体呈上升趋势。乌鲁木齐霾天气的AOD日均值分布在0.35~1.21之间,塔中站沙尘天气的AOD日均值范围为0.30~2.05。

Aerosol optical property is one of the largest sources of uncertainty in current assessments and predictions of global climatic change.In recent years,the numerous studies have been conducted about the aerosol particles,and so far satellite monitoring and ground-based observations are two important ways for monitoring the Earth′s aerosol properties.Data obtained from ground-based measurement networks are useful for characterizing the ambient aerosol and investigating aerosol and cloud effects on radiative fluxes.CARSNET is a ground-based network and has become a national resource for studying aerosol optical properties over different regions in Xinjiang.In this study,based on the solar photometer data of CARSNET made from 2002 to 2014,the aerosol optical depths(AOD)at 440 nm and Angstrom exponents(AE)between 440 nm and 870 nm were statistically analyzed in three meteorological observation stations(Akedala,Urumqi,Tazhong)in Xinjiang,which were the representative of the underlying surface of mountain,city and desert,respectively.The results show that the values of AOD and AE in Xinjiang increased from north to south.The AOD value in Akedala changed less throughout the year,less than 0.3.The AOD of Urumqi station showed obvious seasonal variation,and the mean value of AOD in winter and spring was 2.17 times of that in summer and autumn.The maximum value,1.02,of AOD in Tazhong station appeared in May,and the minimum value appeared in January,with a single peak,throughout a whole year.There is a period of large AOD mainly concentrating between March and July.The range of AE value in Urumqi is in between 0.56 and 0.93,in the Akdara station was in between 0.64 and 0.90 and in the Tazhong station of the desert area was in between 0.10 and 0.58.The aerosol characteristic values were generally larger in winter in the northern Xinjiang,represented by Akdara and Urumqi,which dominated by small particulate matter such as anthropogenic emissions,while in the South Xinjiang,represented by Tazhong,the values were larger in spring and mainly dominated by sand dust.In terms of the seasonal changes,the AOD in Urumqi station showed a general downward trend,while in Tazhong and Akedala stations there were an overall upward trend.Results of aerosol optical properties research during severe haze-fogs in Urumqi station were studied.The AOD value of haze in Urumqi ranged from 0.35 to 1.21,and the arithmetic mean of AOD in haze is 1.63 times of the yearly average.Results of aerosol optical properties research during dust-sand storms in Tazhong station were studied.The AOD range of dust-sand weather in Tazhong station was in between 0.30 and 2.05,among which the average value of sandstorm was 1.04.Although this work is based on the longest and most extensive set of ground-based observations of aerosol optical properties made in China to date,it is just a first step towards understanding what controls the aerosol populations.More detailed work is needed in the future.