Retrieval Of Aerosol Optical Depth By Hyperspectral Remote Sensing And Its Environmental Impact

Aerosol plays an important role in global climate change and air pollution, and also an essential parameter in quantitative remote sensing. The author seeks after an effective way to retrieve aerosol optical depth (AOD) for urban area with dense population and industrialization. Three-level remote sensing monitoring "Satellite -airborne - surface" was ideated with MODIS, OMIS and sun-photometer to retrieve urban aerosol optical depth.In the paper, the author compared three AOD retrieval methods and analyzed the applicability and limitation of each method, including ground-based remote sensing with sun-photometer.After introducing characteristics of hyperspectral data and pretreatment processes, the author analyzed spectral feature of typical objects. High contrast surfaces were used to retrieve AOD over Shanghai city from OMIS, on October 7th 2002. The primary results indicate that AOD is about 0.175-0.314 between 502nm to 590nm band. AOD under boundary layer can be retrieved from high spatial and high spectral resolution airborne imagery.Based on a radiative transfer model, MODIS red/blue-band data were used to estimate surface reflectance, aerosol model, aerosol composition, water vapour and O3. Urban surface characteristics and double-pixel contrast were taken into account to set up a look-up table of apparent reflectance - surface reflectance - AOD and to retrieve AOD from MODIS.A simple seasonal relation is created between meteorological visibility and MODIS AOD data. The seasonal aerosol scale height data were obtained for Shanghai urban area: 1251m, 1957m, 791.7m and 776.4m, respectively for each season. Based on these data, the regional visibility distributions for each season over Shanghai urban area were derived, which confirmed that Shanghai city has low visibility in spring and winter. Shanghai urban area has visibility lower than 10km contour. Low visibility areas were obviously located at Yangpu, Taopu and Wusong industrial parks.MODIS AOD product and direct sun-photometer AOD were used to analyze aerosol optical variety characteristics. MODIS AOD values were compared with surface pollutant and meteorological data. There is a good relation between AOD and PM10. The maximum AOD days often come with high relative humidity, low wind velocity, low visibility conditions which were not good for pollutant diffusion.The factors were reduced into 5species by factor analysis to estimate air pollution:...