Study On Monitoring Urban Air Pollution Using Quantitatively Remote Sensing Method

Since1980s, the process of industralization and urbanization has been speed up in China. Because of deficiency of environmental treatment, air pollution has been becoming more and more serious in urban area. Despite of clean production and lower intensity of pollution discharge in past10years, air pollution is still one of the most serious challenges to sustainable developement. However, monitoring pollution status routinely in a large area is difficult because of limit monitoring sites. Large scale monitoring can be carried out using remotely sensed data because of its macroscopic charactoristics, real-time performance and low cost in economy.Based on the atmospheric radiative transfer theory, a set of practical and feasible methods are put forward to moniter urban air pollution through the experimental researches on dynamicly monitering air pollution in Zhengzhou city in2006-2011by quantitatively remote sensing methods using Terra/MODIS(moderate resolution imaging spectroradiometer) data, and following conclusions can been drawn:1) A modified algorythm is developed to retrieve aerosol optical depth (AOD) in urban area. First, the radiance is scaled with thermodynamic temperature retrieved with simultaneous remote sensing data and band combination defined according to the correlation analysis with ground-based measurements. Indepent variables are nonlinear-transformed while regression analyses are carried out. Meanwhile, the data are grouped according to NDVI (normalized difference vegetation index) values.2) The regression model between AOD and air pollution index (API) has high accuracy after corrected by aerosol scale height (ASH), Angstrom wavelength exponent and water vapor amount (WVA). Using the model, API distribution maps can be drawn daily, which make up the defect of routine air monitoring.3) Retrieval of urban land surface temperature (LST) using MODIS data is worked out by a modified algorithm based on Qin’s algorithm. The accuracy of retrieval improves markedly after modifing the computing methods of atmospheric transmittance and land surface emissivity according to the radiance characteristics of urban land objects.4) The retrieval algorythm of water vapor amount (WVA) using MODIS data is improved at the base of two-three method. It is opt to retrieve WVA in urban areas.5) The dynamic changes of AOD, Anstrom wavelength exponent, aerosol scale height (ASH) and API are analized in Zhengzhou city from2006to2011, which indicates:*AOD is highest in summer, spring and autumn following and minimum in winter, annually except for2009.*The seasonal variation trend of Angstrom wavelength exponent in built-up area is consistent with agricultural land, highest in summer, spring and autumn following and lowest in winter. Overall, aerosol Angstrom exponent is lower in the urban center area than the surrounding area.*ASH takes a clear upward trend, only a slight decrease in2009. It is highest in summer and lowest in winter annually. ASH spatial pattern is consistent with AOD but ASH has little difference, no more than30m. ASH in suburb is getting closer to the center city.*API is higher in the urban center area than the surrounding area and increasing gradually in the urban center area and decreasing in the surrounding area.