新疆典型城市气溶胶光学厚度变化特征

利用2006~2017年Aqua-MODIS C006气溶胶日产品数据，选取新疆地区11个代表性城市进行分类，分析典型城市的AOD近12a变化趋势及特征.结果表明：2006~2017年间，除乌鲁木齐市AOD小幅度上升外，其余10个城市AOD均出现不同程度下降，北疆城市年均降幅较小，吐鲁番市12a间AOD下降了0.13，为哈密、焉耆等同纬度城市群中的最大降幅，南疆城市AOD年均降幅最为显著，阿克苏、喀什、和田和若羌地区AOD分别下降了0.18、0.16、0.16和0.09；AOD空间分布上，南疆为AOD峰值中心，年均值达0.50以上，北疆和东疆地区AOD年均值维持在0.20~0.22；同时，AOD具有典型的季节变化特征，春季为AOD峰值季节，夏季次之，秋、冬季AOD较低；此外，12a间新疆全区AOD出现不同程度降低，其中南疆沙尘源区为AOD下降的典型区域，减少区域呈现出沿昆仑山脉自南向北的带状分布.

Variation in aerosol optical depth over the typical cities in the Xinjiang region

Eleven representative urban areas in the Xinjiang region were selected for classification based on Aqua-MODIS C006 aerosol daily product data from 2006 to 2017, and the variations in AOD were studied for the 11cities in Xinjiang. The results showed that the AOD decreased in different degrees except in Urumqi during 2006 to 2017. On the contrary, AOD for the Urumqi area varied in a small increase during the same period. The average annual decline of AOD in the northern Xinjiang cities was relatively small, the AOD for Turpan decreased by 0.13 during the 12 years, which was the largest decline in the Hami and Yanqi urban agglomerations at the same latitude. The average annual decline of AOD in the southern Xinjiang cities was the most significant, the AODs decreased by 0.18, 0.16, 0.16 and 0.09 in Aksu, Kashgar, Hotan and Ruoqiang, respectively. The peak of the spatial distribution of AOD was in the southern Xinjiang, with an annual average higher than 0.50, and the annual average values of AOD in the northern and eastern Xinjiang were maintained at about 0.20 to 0.22. Meanwhile, AOD had seasonal variation characteristics, with a peak in spring, followed by summer, autumn and winter. In addition, the AOD decreased in different degrees in the Xinjiang region in the past 12 years, the source area of dust aerosols in the southern Xinjiang was the main area of AOD decline, and the reduction area showed a belt shape along the Kunlun Mountains from south to north.