基于AERONET的西亚地区气溶胶光学特性

Study on aerosol optical properties over the West Asia region using AERONET data

利用AERONET 10个站点的Level2数据分析得到2010—2017年西亚地区多个气溶胶参数(光学厚度(Aerosol Optical Depth,AOD)、吸收光学厚度(Absorption Aerosol Optical Depth,AAOD)、波长指数α、粒子体积谱和单次散射反照率(Single Scattering Albedo,SSA))的季节、年际和日变化特征。结果表明,西亚10个站点AOD、AAOD、α和SSA的多年总平均值分别是0.245±0.094、0.030±0.006、0.889±0.247和0.918±0.016,粒子体积谱呈双峰分布。各站点的气溶胶光学参数呈现明显的季节和区域差异。AOD总体表现为春夏季大,秋冬季小。受沙尘影响,各站点α最小值和粗粒子体积浓度峰值均出现在春季,但α最大值呈现明显区域差异,其在阿拉伯半岛站点多出现在冬季,而环地中海站点出现在夏季。此外,阿拉伯半岛站点AAOD夏秋季大、冬春季小,SSA春夏季大、秋冬季小;而环地中海站点AAOD冬春季大、夏秋季小,SSA夏秋季大、冬春季小。除了季节变化外,两地区气溶胶的日变化也不同。阿拉伯半岛站点年平均AOD的日内差异普遍比环地中海站点剧烈,其中沙漠站点呈明显的早晚高,中午低的特征。从年变化来看,除TEP站的α值和ERD站的AAOD值呈显著下降趋势外,其他站点各光学参数的变化趋势均不显著。

In the present study,the aerosol optical properties,including aerosol optical depth(AOD),absorption aerosol optical depth(AAOD),ngstr m exponent(α),volume size distribution(VSD)and single scattering albedo(SSA),for 10 cities in the West Asia region are analyzed in terms of seasonal,annual and diurnal scales based on the AERONET Level2 dataset during the period of 2010-2017.The results show that the respective averages of AOD,AAOD,αand SSA are 0.245±0.094,0.030±0.006,0.889±0.247 and 0.918±0.016,with the VSD exhibiting bimodal spectra.The results reveal significantly different features throughout the various seasons and regions.In general,the higher AOD occurs in spring and summer,while the lower one occurs in autumn and winter.As a result of dust storms,both the minimum ofαand peak of volume concentration for coarse particles appear in spring.However,the maximum ofαis regionally different,respectively exhibiting the maximum in winter and summer at the Arabian Peninsula and Mediterranean sites.At the Arabian Peninsula sites,the higher AAOD occurs in summer and autumn,while the lower one occurs in winter and spring.For the SSA of the Arabian Peninsula sites,the higher one is found in spring and summer,while the lower one occurs in autumn and winter.At the Mediterranean sites,the higher AAOD is shown in winter and spring,while the lower one occurs in summer and autumn.The region also shows the higher SSA in summer and autumn,with the lower one occurring in winter and spring.In addition,the diurnal variation characteristics of AOD also differ in these two regions.The diurnal variation of annual mean hourly AOD at the Arabian Peninsula sites is much more fluctuant than that at the Mediterranean sites.In addition,the AOD of desert sites exhibits higher values in the morning and evening,while being lower at noon.For the annual trend,aside from a significant decreasing trend ofαoccurring at TEP and AAOD at ERD,no obvious variation trend is shown for the optical properties at all of the sites.