MODIS 3 km气溶胶光学厚度产品检验及其环境空气质量指示

分析了MODIS C006 3 km卫星遥感气溶胶产品的算法流程,并与AERONET观测数据进行对比验证,综合新疆阿克苏地区地面空气子站1年的颗粒物质量浓度(PM10)、环境气象资料(能见度、湿度等),评估了该高分辨率气溶胶产品的精度和稳定性.分析表明,MODIS 3 km AOD与AERONET地基AOD(Issyk-Kul)的相关系数(r)达到0.8836,满足期望误差要求,但存在高估;研究区AOD和PM10存在同步变化趋势,新疆阿克苏市区2个空气子站PM10质量浓度与AOD的相关系数(r)均大于0.55,直接对比的相关性好于类似研究;经高度订正和湿度订正后AOD-PM10的相关系数和拟合优度均有所提高,标准误差和变异系数均下降,但提升并不明显.这一相关性结果与研究区本底气象环境条件有关.MODIS 3 km AOD的季平均结果表明,阿克苏地区AOD存在显著的季节性变化,春季明显高于其他季节,主要城市春季平均AOD在1.5以上,夏季和秋季AOD均值基本介于0.6~0.7之间,阿克苏市主城区夏秋季AOD季均值仍在1.0以上,反映人口集聚、城市交通工业发展等大气人为污染的增加导致AOD的增高.结果表明,MODIS C006 3 km AOD产品质量稳定,其月、季平均等长时间尺度结果有更好的空间覆盖,可满足区域环境空气质量评估的需要.

Validation of MODIS 3 km aerosol optical depth product and its air quality indication

The present study aimed to analyze the algorithm of MODIS C006 3 km satellite aerosol product by using atmospheric concentrations of airborne particulates (PM₁₀) and meteorological data (e.g.visibility and relative humidity) collected from a metrological monitoring station (1a) at Akesu of Xinjiang. The precision and stability of this aerosol product was compared with the observed data of AERONET. The results revealed that there was a close and positive correlation between the data from MODIS C006 3 km product and those from the ground station AOD (Issyk-Kul) (r=0.8836). Although the observed precision of MODIS was within the acceptable range, it overestimated the PM₁₀ concentration. AOD and PM₁₀ followed similar variation trends and the correlation between PM₁₀ concentrations at the two meteorological stations in Akesu city was 0.55, which was significant and better than those reported in similar studies. When AOD was corrected against vertical aerosol heights and relative humidity, the correlation was improved but not significantly with reduced standard errors and covariance.There was a significant seasonal variation in MODIS 3 km AOD, with the highest in the spring above 1.5 and only 0.6~0.7 in the summer and autumn. However, within the city area of Akesu, the average AOD remained >1.0 even in the summer and autumn, probably due to the high density of population, transport and industrial activities. In summary, the quality of MODIS C006 3 km AOD product was stable, with improved spatial coverage based on monthly and seasonal mean values. It can satisfactorily meet the requirements of long-term monitoring and regional-scale assessment.