Algorithm Of Land Surface Albedo For FY-3C MERSI

The Surface Albedo characterizes the reflection ability of the surface to solar radiation,which is an important continental table characteristic parameter affecting the radiation and energy balance of the earth system.The Surface Albedo determines the distribution process of radiant energy between the earth's surface and the atmosphere,is a key factor in the climate model,and has important contributions in the study of local climate change and the improvement of terrestrial process patterns^[2].The purpose of this paper is to use the reflectance and angle data of FY-3C MERSI to invert the global Surface Albedo and provide a technical reference for the operational production of FY-3C MERSI Surface Albedo products.The main research contents and achievements of this paper are as follows:?1?FY-3C MERSI data preprocessing.The FY-3C MERSI 250m resolution band1-4 Surface reflectance was obtained by pre-processing the FY-3C MERSI original HDF data,including radiometric calibration,geometric correction,image cloud detection and 6S atmospheric correction.Among them,the image automatic matching technology is used for geometric precision correction;the spectral validity threshold method is used for cloud detection and removal;the 6S atmospheric radiation transmission model is combined with the FY-3C MERSI spectral response function to perform atmospheric correction on the FY-3C MERSI data to obtain 4 band FY-3C MERSI surface reflectance data.The pre-processed FY-3C MERSI surface reflectance data was cross-validated using the MODIS surface reflectance product in the verification area.The results showed that the corrected image area of the verification area was clearer and the contrast was higher.The correlation between the corrected reflectance and the MODIS surface reflectance product is higher than that before the correction,and the maximum correlation coefficient reaches 0.9187,which proves the effectiveness of the 6S atmospheric correction method for the atmospheric correction of the FY-3C MERSI data.?2?FY-3C MERSI Surface Albedo inversion method.Analyze the advantages and characteristics of conventional BRDF models such as radiation transmission model,geometric optical model and semi-empirical model.According to the FY-3C MERSI sensor and data characteristics,the RossThick-LiTransit BRDF kernel model was selected as the inversion model of the FY-3C MERSI Surface Albedo.The model coefficients were fitted by the constrained linear least squares method,and the BRDF model was angularly integrated to obtain the narrow band black-sky albedo and white-sky albedo in the FY-3C MERSI band with 1⁴,and the spatial resolution was250m.Based on the 6S radiation transmission model and the USGS ground reflection spectrum data,the Surface Albedo values of various surface underlying surfaces of the FY-3C MERSI range are simulated.The multivariate linear regression method was used to analyze the linear relationship between the narrow band Surface Albedo and the broad band surface albedo,and the conversion equation of the FY-3C MERSI narrow-band surface albedo to the broad band surface albedo conversion was obtained.The broad band surface black-sky albedo and broad band surface white-sky albedo of FY-3C MERSI visible light band?0.4-0.7?m?were calculated by the conversion equation.?3?Cross-validation analysis of the inverted FY-3C MERSI global surface albedo data with MODIS,CGLS,and GLASS Surface Albedo products in four verification areas.The comparison results show that the correlation coefficient between the narrow band and broad band Surface Albedo of FY-3C MERSI and the three similar products is mostly above 0.75,the overall absolute deviation is 0.068,and the minimum root mean square error is 0.02.The results show that the FY-3C MERSI Surface Albedo products show good agreement with the MODIS,CGLS and GLASS Surface Albedo products in four narrow and visible light bands.The inversion algorithm can lay the foundation for the commercial production of FY-3C MERSI surface albedo products.