The influence of non-static sea ice on Antarctic and Southern Ocean numerical weather prediction

Abstract

Although operational weather forecasting centers are increasingly using coupled atmosphere-ocean-ice models to replace atmosphereonly models for short-term (10 days) weather forecasting, the influence of sea ice on such forecasting has yet to be fully quantified, especially in the Southern Ocean. To address this gap, a polar-specific version of the Weather Research and Forecasting model (Polar WRF) is implemented within a circumpolar Antarctic domain to investigate the impact of daily-updates of sea ice concentrations on short-term weather forecasting. Apart from some steep plateau regions adjacent to the Antarctic continental margin, Polar WRF shows good forecast skill in Antarctic surface variables. A statistically significant improvement in nearsurface temperature and humidity is shown from +96 hours to +192 hours when assimilating daily sea ice concentration into the model. Improvements in model performance are enhanced during July through September, which is a period of late sea ice advance. Regionally, model improvements are shown to encompass almost all sea ice regions, although marked in the Ross and Weddell seas sectors. The surface heat budget balance also shows remarkable improvement in outgoing radiative heat fluxes and both sensible and latent heat fluxes after 48 hours. Our results demonstrate the non-negligible effect of including daily-updates of sea ice concentrations in numerical weather forecasting, and endorsing the necessity of a fully coupled atmosphere-ocean-ice model in operational high-latitude Southern Hemisphere weather forecasting.