中国气溶胶光学厚度的时空分布及影响因素分析

基于1980~2017年MERRA-2再分析产品中的气溶胶光学厚度（AOD）数据，结合趋势分析和时空地理加权回归模型（GTWR）等方法，分析中国AOD的时空变化特征，从时空异质性视角量化自然地理和人类活动对AOD的综合影响.结果表明，1980~2017年AOD以0.0028a^-1的速率呈显著上升趋势，而2009~2017年AOD以0.0083a^-1的速率呈显著下降趋势.2008年前后为AOD由升到降的转折期，可能与2007年生态文明建设和2008年全球经济危机有关.胡焕庸线以东地区为AOD高值区，以人为气溶胶为主，近40a来AOD值呈显著上升趋势；胡焕庸线以西地区为AOD低值区，以自然气溶胶为主，AOD值基本不变.气温、气压、黑炭气溶胶排放和硫酸盐气溶胶排放与AOD呈正相关，降水、风速、NDVI和GDP与AOD呈负相关.AOD与影响因子间的关系具有时空异质性.从时间变化来看，降水、风速、NDVI、GDP的回归系数具有一致性，而气温、气压、黑炭气溶胶排放、硫酸盐气溶胶排放在不同年份的回归系数有正有负；从空间变化来看，中国北方地区气温与AOD间呈负相关，南方地区二者呈正相关.

Spatial-temporaldistribution and impact factors of aerosol optical depth over China

Based on the MERRA-2reanalysis datasets of aerosol optical depth (AOD) during 1980~2017, spatial-temporalvariations of AOD and joint effects of natural and anthropogenic factors on AOD values over China were quantitatively analyzed with trend analysis and geographically and temporally weighted regression (GTWR) from spatial-temporalheterogeneity perspective. The results showed that AOD values in China hold a significant upward trend (0.0028a^-1) during 1980~2017 but a downward trend (-0.0083a^-1) during 2009~2017. The period around 2008was a turning point in AOD trends, probably owing to the construction of ecological civilization in 2007 and theglobal economic crisis in 2008. Secondly, the Hu Huanyong line was the geographical border of aerosol concentration, properties and trends in China. The distribution of AOD since 1980 demonstrated the characteristics of high in the east, low in the west, increasing in the east, and basically unchanged in the west, dominated by anthropogenic aerosols in the east, and dominated by natural aerosols in the west. Lastly, the AOD was positivecorrelated with precipitation, temperature, surface pressure, black carbon aerosol emission and SO₄ aerosol emission, while was negatively correlated with wind speed, normalized difference vegetation index (NDVI) and gross domestic product (GDP).The relationship between AOD and impact factors varied over time and space. From the perspective of temporal variations of estimated coefficients of GTWR model, the effects of influencing factors such as precipitation, wind speed, NDVI and GDP on AOD values over time were consistent; while the temporal variations of other factors, including temperature, surface pressure, black carbon aerosol emission and SO₄ aerosol emission, exhibited changedinconsistently. From the perspective of spatial variations,the correlation between temperature and AOD wasnegative in northern China, while positive in southern China.