Effects of advanced atmosphere-sea ice exchange coefficient in the Korean Integrated Model (KIM)

The Korea Institute of Atmospheric Prediction Systems (KIAPS) is developing a spatio-temporal integrated coupled modeling system that is capable of forecasting from one week to two months. This system is based on the Korean Integrated Model (KIM) and incorporates the Nucleus for European Modelling of the Ocean (NEMO) framework to simulate ocean and sea ice components. While the coupled model’s mid-term prediction performance is comparable to that of the atmosphere-only model, it exhibits a significant cold bias in the polar regions when evaluated against reanalysis data such as ECMWF reanalysis version 5 (ERA5).
Polar regions, characterized by sea ice, present unique challenges due to the complex interactions between the atmosphere and the ocean. In winter, reduced sea ice formation allows more heat to transfer from the ocean to the atmosphere, further warming the air. Accurate simulation of these regions requires a further understanding of atmosphere-sea ice interaction. In this study, sensitivity tests of the atmosphere-sea ice exchange coefficient were conducted to optimize the momentum and heat transfer in the Arctic and Antarctic. The exchange coefficients were fixed at 0.0014 in the control run, while two parameterization methods, modulating sea ice roughness length, were applied to the experimental run. The results revealed opposing outcomes: one method caused atmospheric warming, while the other resulted in cooling, implying significant uncertainty in calculating the heat exchange coefficient. Further analysis of atmospheric and sea ice dynamics within the coupled KIM will determine the most suitable parameterization approach for accurate polar region simulations.

Acknowledgements. This work was carried out through the R&D project “Development of a NextGeneration Numerical Weather Prediction Model by the Korea Institute of Atmospheric Prediction Systems (KIAPS)”, funded by the Korea Meteorological Administration (KMA2020-02212).