Aerosol Optical Depth Based On Satellite Observations In China

This paper investigated a comprehensive evaluation of satellite aerosol products in China, and then explored aerosol optical depth on the basis of satellite data and ground observations. Firstly, Moderate Resolution Imaging Spectradiometer(MODIS) on Terra and Aqua satellite retrieved aerosol optical depth(AOD) products over China were comprehensively validated by the data of Sun photometer(CE-318) at the Aerosol Robotic NETwork(AERONET). Furthermore, the special and temporal distribution characteristics of AOD over China were studied by Terra/Aqua-MODIS aerosol products included two different algorithm(Dark Target and Deep Blue). Meanwhile, according to different geographical characteristics in China divided areas, the regional AOD nearly10years of changing trends were discussed. In final, the applicability of the satellite data and the distribution characteristics of AOD were analyzed above the arid/semi-arid region of Loess Plateau.(1) Terra/Aqua-MODIS AOD products(Dark Target) are suitable for quantitative analysis of aerosol loading over northern, southern and most of the middle and lower reaches of Changjiang River in China. But more sites to satellite will be verified over the northeast, Xinjiang and the Tibetan plateau area in China. For different surface features, MODIS AOD compares better with those from photometers at the sites characterized by intensive vegetated suface and less human activity, such as Xinglong site. But poor correlations are found at urben sites characterized by complicated underlying surfaces with sparse vegetation and water cover. The errors are analyzed from aspects of the estimation error of surface albedo and aerosol model assumption.(2) Aqua-MODIS deep blue algorithm AOD products can better reflect the change characteristics of the atmospheric aerosol in comparision results of hexi corridor areas. Correlation coefficients are above0.6, expecially in Jingtai and Minqin sites, R values were0.76and0.64, show that the deep blue algorithm for Aqua-MODIS is a good supplement for the retrieval of AOD above bright suface of deserts of northwest China. The applicability of aerosol products(Dark Target and Deep Blue) are relatively poor in Lanzhou city, appearing systematically underestimate about0.3. Maybe due to pollution is serious and anthropogenic aerosol affected, need to strengthen the regions’s ground observation, and understanding of the aerosol physical and chemical characteristics.(3) The spatial distributions of AOD retrieved by Terra-MODIS over China are same as those by Aqua-MODIS. The high AOD values occur in Sichuan basin, northern and the middle and lower reaches of Changjiang River areas. On the whole, the AOD in north of China show a weak rising trend, the rest areas has declined, show that some of the ecological environment protection measures obtains certain result in our country. Aqua-MODIS deep blue of the AOD data was given a desert region in northwest China on the surface of the AOD season distribution characteristics. From2003-2010, AOD values of tarim basin and the qaidam basin showed a rising trend, in junggar basin has a weak down trend, and west Inner Mongolia and hexi area smooth change trend.(4) The loess plateau semiarid areas has special surface and complex aerosol type. Correlation coefficients of550nm AOD retrieved from sun photometer data and that from Terra/Aqua MODIS data are0.69/0.62. Additionally, Terra/Aqua MODIS data are used for analyzing spatial and seasonal characteristics of AOD above the arid/semi-arid region of Loess Plateau. Results show that east region has larger AOD, and local maximums are corresponding to capital cities of those provinces. AOD above the arid/semi-arid region reaches its maximum in spring(mainly by the dust effect), small summer, autumn AOD minimum, winter AOD larger (mainly by the coal emissions affected).