基于MODIS的长三角地区气溶胶时空变化规律及其气象解释

基于2008—2017年的MODIS气溶胶光学厚度(AOD)数据、实测气象观测数据,探究了长三角地区的AOD时空分布规律,并分析了AOD与多个气象要素的相关性,以对AOD的时空变化作出合理的气象解释。结果表明:1)从时间分布来看,长三角地区年均AOD呈周期性波动变化趋势,2011年出现峰值0.83,2014年AOD开始迅速下降,至2017年达到最低,较2014年相比下降22.8%,这与政府实施的固体颗粒物控制排放政策有关;每年夏季(6,7月)AOD出现最大值,这主要是海洋上大量的海盐气溶胶颗粒和水汽扩散到内陆地区造成的。2)从空间分布来看,长三角AOD高值区均分布在江苏南部以及徐州一带,2014年以来AOD高值范围逐步缩小;浙江地区AOD明显低于苏沪地区,这与浙江地势高起伏较大密切相关。3)从相关性方面来看,AOD变化与气温、相对湿度变化之间呈较好的正相关性,而与风速的相关性较复杂,这可能受风向的不确定影响;夏季气温高、湿度大,因此出现大范围的AOD高值区;冬季气温低、空气中水汽含量低,固体颗粒物对于AOD贡献率较大,因此冬季AOD变化能够在一定程度上反映空气污染状况。该研究结果可为长三角地区气溶胶评估、空气质量归因分析、空气质量改善等相关研究提供参考。

SPATIAL AND TEMPORAL CHANGES OF AEROSOL IN YANGTZE RIVER DELTA AND ITS METEOROLOGICAL INTERPRETATION

Based on MODIS aerosol optical depth(AOD) data and meteorological observed data from 2008 to 2017, the spatial and temporal distribution of AOD in the Yangtze River Delta area was summarized, which was then explained by analyzing the correlation between AOD and meteorological factors. The results showed that: 1) the annual average AOD fluctuated periodically, which showed its peak value of 0.83 in 2011, and declined rapidly from 2014, with an obvious decrease of 22.8% in 2017 compared with 2014. In addition, the peak value of monthly mean AOD appeared in summer, which was mainly caused by the diffusion of large amount of sea salt aerosol particles and water vapor from the ocean in summer; 2) in terms of spatial distribution, the AOD high value in Yangtze River Delta mainly distributed in southern Jiangsu and Xuzhou area, and the area with AOD high value had gradually narrowed since 2014; the AOD of Zhejiang Province was significantly lower than the other areas, which was closely related to the high topography of Zhejiang Province; 3) the change of AOD had a good positive correlation with the temperature and relative humidity, but the correlation with wind speed was poor and complex, which may be affected by the uncertainty of wind direction. In summer, due to high temperature and humidity, most areas showed high AOD values, and the low temperature and air moisture content in winter caused low AOD. However, the contribution of solid particles to AOD was large in winter, so the change of AOD may reflect the air pollution in winter. The results can provide a reference for aerosol assessment, air quality attribution analysis and air quality improvement in the Yangtze River Delta in future.