Evaluation of daily mean OLR by combining FY-3 dual-satellites
The Outgoing Longwave Radiation(OLR)of the top of the atmosphere is an important component of radiation energy balance.The FY-3D and FY-3E polar-orbiting meteorological satellites,launched in November 2017 and July 2021 respectively,carry the medium resolution spectral imager(MERSI)Ⅱ and low light instruments.Both instruments can retrieve OLR using two water vapor channels and two window channels.In this study,on the basis of the introduction of the MERSI OLR inversion algorithm of the Fengyun satellite,the instantaneous OLR retrieval accuracy of FY-3D and FY-3E MERSI is compared by using the instantaneous observation data of Aqua CERES OLR.Comparison results show that the instantaneous OLR retrieval accuracy of FY-3D and FY-3E is basically the same as the instantaneous OLR data of Aqua CERES.The Root Mean Square Error(RMSE)of FY-3D and FY-3E MERSI OLR is between 6 and 7 W/m2 compared with that of Aqua CERES OLR.This result reflects that although the performance of the MERSI instruments of the FY-3D and FY-3E satellites have differences,the OLR retrieval capabilities of the two satellites are comparable.The comparison results of the daily average OLR data based on CERES between the single and joint calculations of FY-3D and FY-3E show that the daily average OLR calculated on the basis of the four times of the two satellites per day is 3-4 W/m2 higher than that calculated twice a day for a single satellite.The global daily average OLR data from June to December 2022 were selected as an example.Compared with the daily average OLR of CERES,the daily average OLR obtained by two FY-3 satellites is remarkably improved in comparison with the RMSE of the daily average OLR calculated by a single satellite.This result shows that the daily observation data of multiple polar-orbiting meteorological satellites can reflect the diurnal variation characteristics of OLR well.The comparison involves the spatiotemporal matching of data,reprojection,and resampling schemes affects the validation results.Compared with CERES,the difference between the retrieval OLR of the low-temperature target is higher than that of the high-temperature target regardless of the daily average OLR calculated on the basis of the single or double satellites of FY-3.The reasons for this are multifaceted and must be further analyzed.Research results show that the joint application of multiple polar-orbiting satellites with a certain instantaneous observation interval can effectively improve the calculation accuracy of the daily average OLR in the cloud area.However,how to construct the daily variation model of OLR and deepen the calculation method of the daily average OLR must be further studied.
FY-3,multi-satellites,outgoing longwave radiation,assessment,diurnal variationmedium resolution spectral imager,cloud and earth radiant energy system,cloud cover
万方数据
维普
