The influence of time varying sea-ice concentration on Antarctic and Southern Ocean numerical weather prediction

Abstract

Although operational weather forecasting centres are increasingly using global coupled atmosphere-ocean-ice models to replace atmosphere-only models for short- and medium-range (10-day) 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 is implemented with a circumpolar Antarctic domain to investigate the impact of daily updates of sea-ice concentration on short- and medium- range weather forecasting. A statistically-significant improvement in near-surface atmospheric temperature and humidity is shown from +24 hours to +192 hours when updating the daily sea-ice concentration in the model. The forecast skill improvements for 2 m temperature and dewpoint temperature are enhanced from June to September, which is the period of late sea-ice advance. Regionally, model improvement is shown to occur in most sea-ice regions, although the improvement is strongest in the Ross Sea and Weddell Sea sectors. The surface heat budget also shows remarkable improvement in outgoing radiative heat fluxes and both sensible and latent heat fluxes. This idealised research demonstrates the non-negligible effect of including more accurate time-varying sea-ice concentration in numerical weather forecasting.