The Antarctic ice shelf surface temperature retrieval from Chinese MERSI series data

The ice shelf surface temperature (IST) is a critical environmental and climatic parameter. Current wide-swath IST products, such as those from the Moderate Resolution Imaging Spectroradiometer (MODIS) and Advanced Very High Resolution Radiometer (AVHRR), typically have a spatial resolution of around 1000 m. In contrast, the Medium Resolution Spectral Imager (MERSI) provides a thermal infrared channel with a wide swath of 2900 km and a higher spatial resolution of 250 m. In this study, we developed a practical single-channel algorithm to retrieve ISTs from MERSI series data, addressing several key challenges: (1) the wide range of incidence angles; (2) the unstable, snow-covered ice surface; and (3) variations in atmospheric water vapor content. To enhance retrieval accuracy, we simulated directional emissivity to mitigate the limitations of assuming a constant emissivity. Simulations were conducted for various ice surface types, with the sun crust type identified as the most suitable for IST retrieval. Additionally, real-time water vapor content was estimated using a band ratio method based on MERSI near-infrared data. The proposed algorithm demonstrates improved accuracy and reliability compared to the original approach. The retrieved IST values are higher than those from IceBridge measurements, with a mean bias of 1.06 K and an RMSE of 1.76 K. Validation against AWS measurements further confirms the algorithm's performance, yielding an RMSE of about 2.5 K for both MERSI-I and MERSI-II data.