Retrieval Study On Sea Ice Concentration Using Multi-Angle Observing For Passive Microwave

Passive microwave remote sensing using space borne radiometer is an important method to detect sea ice concentration.The highest spatial resolution of 6.25 km in the current sea ice concentration products can be achieved by using the polarization brightness temperature difference of the 89 GHz channel of AMSR-E combined with ASI algorithm,but additional low-frequency brightness temperature data is needed for weather filter.SMOS observation method by using multi-angle provides a new idea: at 89 GHz band along the orbit scanning by using one dimensional synthetic aperture radiometer with mechanical scanning can be realized on multiple incidence angle for observing a single pixel.Making full use of the brightness temperature under multiple incidence angle caused the sea ice in the process of information can make up for observation confused with sea brightness temperature information,improving the retrieving accuracy of SIC,achieving high spatial resolution at the same time.In summary,the feasibility study of observing the Arctic sea ice concentration with the brightness temperature information of 89 GHz multi-incident angle is carried out.Firstly,the multi-layer sea ice emission transmission model,Fast sea water Emission transmission Model(FASTEM-5)and Atmospheric Millimeter wave emission transmission model(MPM93)were used to construct the satellite-borne sea ice radiation brightness temperature simulation system,and the sensitivity analysis of 89 GHz between brightness temperature and angle was carried out.Secondly,according to the FY-3C/MWHS independent brightness temperature detection and the ability of multiple incidence angle scanning FY-3C for Microwave Humidity Sounder(MWHS)Arctic brightness temperature data,using the SIC products from ECMWF select areas,clear sky matching using ECMWF data.The response of the brightness temperature curve of MWHS changing incident angle is obtained,and the error analysis is carried out with the result of forward simulation model analysis data.Finally showed that the trend of MWHS observations and model simulation results are consistent,verified the feasibility of the model.Finally,the SIC retrieving algorithm based on angle temperature difference at the 89 GHz is deduced and established.The SIC product of ECMWF and forward simulation system were combined to complete the preliminary inversion verification.The results show that the retrieving of sea ice concentration can be realized by using the brightness temperature difference of incident angle,and the minimum root-mean-square difference(RMSE)weighted average post-processing by using the combination of multiple incident angles can minimize the retrieving error of SIC.When the input Gaussian white noise is 2K,5% SIC error can be obtained.Through the theoretical model simulation of 89 GHz sea ice and sea water,MWHS measured data screening and SICretrieving algorithm verification,the final results prove that continuous angle brightness temperature difference for SIC retrieving can fully expand the distinction between sea water and sea ice,reduce the SIC retrieving error.