Accuracy Test And Error Correction Of Water Vapor From HY-2A Calibration Microwave Radiometer

The water vapor products of Haiyang-2A(HY-2A)Calibration Microwave Radiometer(CMR)are an important data source for global ocean water vapor detection,which is of great significance for the study of global weather system evolution and climate change.In this paper,the accuracy of HY-2A CMR water vapor data in 2015 was tested and evaluated by using the observation data from China’s coastal GNSS operational observation system and IGS island stations.Based on the European Centre for Media-Range Weather Forecasts(ECMWF)data,this paper comprehensively tests the accuracy of CMR water vapor data in 2015 with different indicators of ocean,land and sea ice,and analyzes the spatial and temporal distribution characteristics of the CMR water vapor data.Error analysis and linear deviation correction are carried out for CMR data of anomalous water vapor over land and sea ice in polar seas.The main research contents and conclusions are as follows:1.The basic algorithm of GNSS Precise Point Positioning(PPP)and the Precipitable Water Vapor(PWV)inversion method based on PPP technology are presented,and the principle,basic parameters and data format of HY-2A CMR Water Vapor information inversion are described.2.GNSS evaluation of water vapor mass of HY-2A CMR.Firstly,the spatio-temporal matching principle of GNSS and CMR water vapor data was analyzed,and then the accuracy of HY-2A CMR water vapor products in 2015 was tested and evaluated based on GPS PWV of China coastal operational observation stations and IGS island stations.The results show that the correlation coefficients between water vapor and GPS PWV are all greater than 96%,which indicates that there is a high correlation between them.The mean deviation and root mean square error of water vapor in HY-2A CMR are-0.87 mm and 2.09 mm,respectively,and the mean deviation and root mean square error of water vapor in HY-2A CMR are-0.74 mm and2.08 mm,respectively,compared with the GPS PWV of IGS island station,indicating that the water vapor in HY-2A CMR is in good agreement with GPS PWV.Furthermore,the accuracy of CMR water vapor data in 2015 was further analyzed.It was found that the RMS of CMR water vapor data was basically the same in each month,and the accuracy of CMR water vapor data had no obvious seasonal characteristics.The feasibility of using GNSS technology to evaluate the accuracy of HY-2A CMR water vapor products is verified,and the test means of HY-2A CMR water vapor data is broadened.3.Based on the reanalysis data of the European Mesoscale Weather Prediction Center,the quality of the water vapor data of the 2015 CMR Ocean Marker is evaluated,and the temporal and spatial distribution characteristics of the accuracy of the CMR sea surface water vapor data are analyzed with emphasis.The results show that the correlation coefficient between water vapor and ECMWF PWV in HY-2A CMR is more than 99%,which indicates that there is a high correlation between the two.The mean deviation and root mean square error of water vapor over HY-2A CMR are 0.02 mm and 2.11 mm,respectively,indicating that water vapor over HY-2A CMR is in good agreement with ECMWF PWV.The accuracy of CMR water vapor data has no obvious seasonal variation,but increases with the increase of latitude.The accuracy of CMR water vapor data in the southern hemisphere is slightly better than that in the northern hemisphere,showing obvious spatial distribution characteristics.4.Anomalous data calibration in polar seas.Taking ECMWF reanalysis data as reference,error analysis and linear fitting were carried out for CMR land + sea ice anomaly water vapor data from January to October 2015 in the polar sea area,and the fitting model was used to correct the linear deviation of the data from November and December.The results show that there is an obvious linear system deviation in CMR water vapor data over land and sea ice.After correction,the RMS of CMR water vapor in two regions(near 60°W and near 100°W)is1.68 mm and 1.76 mm,respectively,which is basically consistent with the accuracy of CMR water vapor data over sea.