Retrieval Of Aerosol Optical Depth In Shanghai Using Remotely Sensed Data Of Chinese High Resolution Satellites

The air pollution is an important factor,that can affect the health of our residents,social production activities and regional sustainable development.It is of great significance for environmental governance and regional planning to know about the distribution and change of atmospheric pollution.Satellite remote sensing has the characteristics of wide space coverage,continuous monitoring,and low cost.Aerosol optical depth(AOD),which is obtained by remote sensing,has been used to monitor air quality,especially the inhalable particulate.However,MODIS AOD products,used widely in current,have a low spatial resolution,and it is difficult to meet the needs of regional air quality refinement monitoring.In addition,China's high-resolution earth observations have advanced specifically and a series of domestic high-altitude satellites were launched.It is of far-reaching significance to study the AOD retrieving method based on the domestic high-resolution satellite(GF)to exert its active role in atmospheric environment monitoring.In this paper,the polar orbiting satellites(GF-1)with high spatial resolution and the geostationary satellites(GF-4)with high temporal resolution were used to improve two key issues of AOD retrieving based on deep blue algorithm over Shanghai,that are the aerosol model and surface reflectance.And this is a helpful trials and exploration to expand the application of China-made high-resolution satellites in the regional atmospheric environment monitoring.Following are mainly research results.1.In the aerosol mode,this paper used the aerosol parameter data of 4 AERONET sites in the Yangtze River Delta region for a long time sequence from 2005 to 2012.And we counted different seasons of AOD,aerosol size distribution,complex index of refraction,and single scattering albedo,to set up some local aerosol models.These models replace the aerosol model given in the 6S transfer model and improve the accuracy of AOD retrieving in the study area.2.In the surface reflectance,this paper innovatively combines data MODIS two surface reflectance products MOD09A1(500 m)and MOD09Q1(250 m).The spatial resolution of blue-wave surface reflectance products increased from 500 meters to 250 meters.At the same time,the time series analysis of the blue-wave surface reflectivity extracted a batch of stable reflectivity pixels in the blue band,to participate in AOD retrieving based on deep blue algorithm.The above two improvements increase on spatial resolution and retrieving accuracy,respectively.3.In calculating apparent reflectivity,this paper used the published GF-1 satellite sensor parameters and the widely accepted solar spectral data to calculate the Mean Solar Exo-atmospheric Irradiances(ESUN)value of GF-4 satellite sensor.This parameter is used for the retrieving AOD of GF-4.At the same time,this method can also be used to calculate the apparent reflectivity of other satellite remote sensing sensors.4.Based on the above,GF-1 and GF-4 data were used to achieve a refined AOD result of 250 m resolution over Shanghai,based on the improved deep blue algorithm.Due to the lack of AERONET observations,this paper compared the MODIS AOD products and near-surface particulate data of Shanghai environmental monitoring center.The results showed that the root mean square errors of AOD results of GF-1 and GF-4 compared wiith MODIS AOD products were 0.235 and 0.241 respectively.Correlation coefficients with monitoring stations PM2.5 and PM10 are all above 0.75,up to 0.92.From here we can see that the improved aerosol models and surface reflectance had achieved good effect.