北京市气溶胶的时间变化与空间分布特征

Seasonal variation and spatial distribution of atmospheric aerosols in Beijing

以MODIS气溶胶遥感数据与同期AERONET监测数据为基础,应用统计分析、对比分析、时间序列分析等技术手段,研究了北京地区气溶胶的时间变化和空间分布特征.结果表明,气溶胶MODIS遥感反演数据和同期AERONET监测数据吻合较好,Pearson积矩相关系数为0·789,误差为ΔAOT550=-0.077AOT+0.03.北京地区气溶胶550nm光学厚度AOT和细粒比η的时间变化规律性明显:夏季以城市污染气溶胶为主,光学厚度最高,且具细粒特征;春季城市污染气溶胶和春季沙尘共存,光学厚度比较高,且粗粒占一定比例;冬季以采暖燃煤气溶胶为主,光学厚度不高,但是粗粒占较大比例;秋季大气清澈,气溶胶平均光学厚度仅为0.34.空间分布方面,主要受植被覆盖和产业结构等因素影响,位于西部北部山区的延庆、密云、怀柔和门头沟区气溶胶的光学厚度低,位于东南部平原地区的昌平、顺义、通县、大兴和房山区气溶胶光学厚度总体较高.

The MODIS aerosol optical thickness, AOT550 ,and the fraction of fine mode,η, for Beijing were validated using AERONET monitoring data. The validation result indicated that the accuracy of the MODIS remote sensing aerosol optical thickness is （-0.077AOT ＋ 0.03）. With this validation we believe that the MODIS aerosol product including aerosol thickness AOT and fraction of fine mode η can be used quantitatively to analyze the temporal variation and spatial distribution of the atmospheric aerosol in Beijing. Investigations of aerosol data retrieved for the period 2002.7 -2005.12 showed that summer is characterized by maximum AOT and η, caused by urban pollution haze; winter has moderate AOT accompanied by low η as a result of heating activity. The spring dust in Beijing can be Measured due to its coarse particles. Differences in vegetation cover and industrial activity resulted in a clear spatial distribution of the aerosol in Beijing. Low AOT was observed in the mountain area located in western and northern Beijing as a result of dense vegetation cover and low industrial activity. In contrast, high AOT was observed for the southeastern Beijing plain, where the population is dense and the industry is intensively developed.