Research On Quality Control And Quality Assessment Approach Of Downward Shortwave Radiation And Phonosynthetically Active Radiation Remote Sensing Products

Global radiation energy balance is the basic driving force for the formation andchanges of global climate. It directly determines the cycle of global carbon, water andother substances, and it is the cornerstone in research on global change. As twoimportant components of the radiant energy, downward shortwave radiation (DSR) andphotosynthetically active radiation (PAR) play an important role in the detection,characterization and quantification of surface changes, driving the global and regionalclimate system model, estimation of the global biogeochemical cycles, supportingenvironmental policy and resource management. Quality control (QC) and qualityassessment (QA) of quantitative remote sensing products are important parts in theproduction process. The product’s quality information is valuable for users. Because thealgorithm of DSR and PAR products is complex and more input data are needed,uncertainty sources of products are more.This paper proposed the QC and QA methods of downward shortwave radiationand photosynthetically active radiation products. The polar-orbiting and geostationarydata were combined as inputs to the algorithm for all-sky DSR and PAR (POGDA). Themain contents of the study are:(1) In QC, detailed method of quality control system establishment and qualityassessment had been presented with the design of the general technological frame. Thereliable quality control system was established by algorithm analysis, the productuncertainty analysis, sources of error analysis and quality flag. Then the quality flag filewas generated. The quality information of input data and production process could bechecked by users.(2) In QA, a detailed program of quality assessment was developed for POGDADSR and PAR product. The product was validated using in-situ data. Different temporalresolution, weather conditions, regions, elevations and satellite zenith angles were takeninto account. The accuracy of DSR and PAR product can meet customer’s needs bycomparing the results with the other product and results in the literature. Then theproduct was compared with similar remote sensing products. The product quality information was used for further analysis of quality. The possible sources of error andthe affect factors of quality were analyzed. The product was validated at Beijing site.The coefficient of determination (R~2) was0.92and the relative root mean square error(RRMSE) was10%for the level1product, the quality affect factors were snow cover,water vapor and ozone, the R~2was0.88and the RRMSE was27%for the level2product, the quality affect factor was surface albedo, the R~2was0.82and the RRMSEwas32%for the level3product, the quality affect factor was cloud optical thickness(COT). So the quality control system was reasonable, and it can reflect the qualityinformation of products. Quality report of product was generated at last. Qualityassessment was accomplished by comparing with measured data from92Chinese solarradiation sites. The R~2was0.8289, the mean bias error (MBE)0.7626MJ/m~2(11.02%)and RMSE1.7889MJ/m~2(25.84%).