Study On Aerosol Optical Depth Retrieval Based On GOCI Data By Supported By MODIS Data

With the rapid development of urbanization and industrialization in China,the emission of various atmospheric pollutants is increasing,which makes the city's air quality increasingly worse.In most parts of China,aerosol particles have become major pollutants affecting air quality.Aerosol optical thickness is an important parameter to study the atmospheric environment,and its inversion accuracy and spatial distribution characteristics have always been the hot spots of atmospheric pollution research.At present,inversion of atmospheric aerosol parameters using multi-source satellite remote sensing data is an important means to detect the spatial distribution and changing trends of atmospheric pollutants.It can provide scientific basis and technical support for aerosol monitoring and air pollution remediation.In this paper,GOCI is used as the data source,and the aerosol optical depth(AOD)is retrieved with the support of MODIS data.Compared with other sensors,the GOCI sensor has higher spatial resolution,time resolution and higher signal-to-noise ratio,which is conducive to quickly capturing information of atmospheric dynamic changes and has broad application prospects in remote sensing aerosols.In order to maximize the application potential of GOCI for atmospheric aerosol monitoring,it is particularly important to study the aerosol remote sensing inversion algorithm.Because the GOCI sensor lacks the mid-infrared 2.12m channel,the MODIS dark-pixel algorithm cannot be used to determine the surface reflectance,and the GOCI has eight images at a time interval of 1 hour.The change in surface reflectance between images is obviously affected by the geometric relationship among the sun,the ground and the sensor.So how to accurately determine the surface reflectance of GOCI is the focus of this paper.In this paper,the Yangtze River Delta region is selected as the study area,and the semi-empirical nuclear drive model(Ross-Li model)is combined with the MODIS V5.2 algorithm to determine the surface reflectance of the GOCI observation geometry,then the look-up table established by the 6S radiative transfer model was invoked to retrieve the GOCI aerosol optical thickness from January 2013 to February 2015.The research work and main conclusions of this paper are as follows:(1)The surface bidirectional reflectance of the MODIS and GOCI observation geometries was simulated based on the Ross-Li model using the MODIS BRDF/Albedo product MCD43A1 data,and MODIS surface reflectance is obtained through MODIS V5.2 algorithm.The combination of the three types of surface reflectance can be used to obtain the MODIS surface reflectance in GOCI observation geometry.Then,surface reflectance conversion between the two data sources is performed to obtain the surface bidirectional reflectance of GOCI itself.(2)This paper has completed the band conversion correction of the two sensors to correct the errors caused by different spectral response functions.The surface reflectance curves of 26 typical features were selected from ENVI standard spectral database.The surface reflectance of 26 typical features in the blue wavelength band of the two sensors was calculated by using the spectral response functions of GOCI and MODIS sensors.Finally,a linear regression equation with ?GOCI=?MODIS*1.0247+ 0.0064 was established between the surface reflectance of the two sensors in the blue wavelength region.R2 is 0.9953,which indicates a significant correlation.The equation can be used to convert the MODIS bidirectional reflectance of GOCI observation geometry to the surface bidirectional reflectance of GOCI itself.(3)A spatial comparison of the MODIS AOD inversion rthere esults with the GOCIAOD inversion results was performed.The results show that is a good correlation between the two inversion results,and the correlation coefficient is 0.8002.The accuracy of GOCI AOD inversion results is verified by ground observation data.Verification results with ground observation data show that the correlation between GOCI AOD inversion results and ground observation data is significant.R2 of Taihu is 0.853 and RMSE is 0.0946;R2 of Xuezhenglou is 0.8187,and RMSE is 0.1306.Compared with the correlation and RMSE,the Taihu inversion result is better than Xuezhenglou.At the same time,there is significant consistency in the intraday time trends between GOCI inversion results and ground observations,indicating that GOCI inversion results have the ability to monitor intraday changes in aerosol optical thickness in the Yangtze River Delta region.which show that the results of GOCI inversion have the ability to monitor the changes of AOD in the Yangtze Delta region.The results of spatial analysis and ground verification show that the results of the GOCI AOD inversion in this paper are more reliable.