The change of Arctic sea ice has recently attracted much attention among climate researchers due to the climate effect of “Arctic Amplification”. Sea ice concentration, which is the main parameter of passive microwave remote sensing of sea ice, can characterize the sea ice conditions, which can be used to guide the polar navigation and study the sea ice change in different scales. The sea ice area and sea ice extent can also be calculated by using the sea ice concentration, which is of great significance for the forecast of polar sea ice conditions and the study of climate change. This work discusses how to use the high resolution channels of FY-3B/MWRI (FY-3B/Microwave Radiometer Imager) to retrieve the sea ice concentrations in the Arctic. Based on the ASI (ARTIST [Arctic Radiation and Turbulence Interaction Study] Sea Ice) algorithm, the Arctic sea ice concentration is calculated in this study by improving the tie points of the algorithm. According to the cross calibration of brightness temperatures between the FY-3B/MWRI and the Aqua/AMSR-E (Advanced Microwave Scanning Radiometer-EOS), the differences between the two brightness temperature data are between ±4 K, which will result in a maximum bright temperature difference of 8 K. Accordingly, this study first sets the variation range of the tie points for FY-3B/MWRI centered on the original values of the ASI algorithm to 11.7±8 K for sea ice and 47.0±8 K for open water, separately, with a step length of 1 K. After the combination, 289 series of point value combinations are obtained. Then, the sea ice concentrations corresponding to each set of tie points are compared with those of the AMSR-E L3 product. Meanwhile, the tie points corresponding to the smallest deviation of the two data sets are selected. According to the tie points determined above, this study calculated the Arctic sea ice concentrations based on the FY-3B/MWRI brightness temperatures, hereinafter referred to as the Retrieved Sea Ice Concentration (RSIC). The RSICs in this study are compared with the MWRI Level 2 sea ice concentration product (hereinafter referred to as MWRI). First, the sea ice concentrations obtained from the Aqua/MODIS (Moderate Resolution Imaging Spectroradiometer) reflectivity data from July to September 2011 are used to verify the two data sets. The results show that the bias of RSIC is comparable to that of the MWRI product. However, the standard deviation and root mean square error are significantly reduced. Meanwhile, the accuracy of RSIC is much higher than that of the MWRI product in the areas with a sea ice concentration lower than 95%. Then, the two sea ice concentration data sets are compared with the sea ice concentration product from the University of Bremen (SIC_UB). The bias and the standard deviation between RSIC and SIC_UB are 3.3% and 10.6%, which are lower than the values between the MWRI and the SIC_UB products: 5.9% and 16.4%, respectively. Finally, the time series of the daily averaged sea ice concentration, sea ice area, and sea ice extent from the RSIC, MWRI, SIC_UB, and NSIDC/AMSR-E (National Snow and Ice Data Center/Advanced Microwave Scanning Radiometer-E) sea ice concentration products are compared. The results show that the values of RSIC are significantly lower than those of the MWRI product in three statistical methods and much closer to the AMSR-E and SIC_UB products. In this study, the sea ice concentrations in the Arctic region are retrieved based on the brightness temperatures from the FY-3B/MWRI high frequency channels. The sea ice concentrations in this study have a higher spatial resolution and a better accuracy compared with the FY-3B/MWRI L2 sea ice concentration product, which is conducive to the long-time series study of climate change in the Arctic. © 2022 National Remote Sensing Bulletin. All rights reserved.
