Towards improved representation of sea ice within Antarctic numerical weather prediction

• Main Author: Wang, Z
• Format: Thesis
• Language: unknown
• Published: 2022
• Subjects: Antarctic sea ice; numerical weather prediction; atmospheric reanalysis; atmospheric modelling; Antarctic; Southern Ocean; Weddell Sea; Ross Sea; Weddell; Antarc*; Sea ice
• Online Access: https://eprints.utas.edu.au/47693/

Antarctic sea ice plays key roles in modulating Southern Ocean weather and climate processes. Accurate representation of sea-ice properties is one of the keys for improving predictive skill in polar atmospheric forecasts. However, sea-ice representation is relatively basic (i.e., static sea-ice properties throughout the forecast period and/or with an unrealistic, prescribed thickness/snow cover) in widely-used global and regional forecast models. Poor representation of sea-ice properties in numerical weather prediction (NWP) models may increase errors in forecast surface and near-surface parameters. Although operational weather forecasting centres are increasingly using global coupled atmosphere-ocean-ice models to replace atmosphere-only models for short-term (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 (Polar WRF) is implemented within a circumpolar Antarctic domain to investigate the impact of daily updates of sea-ice concentration on short-term weather forecasting. A statistically significant improvement in near-surface atmospheric temperature and humidity is shown from +48 hours to +192 hours when assimilating daily sea-ice concentration into the model. Improvement in model performance is enhanced from July 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 balance also shows remarkable improvement in outgoing radiative heat fluxes and both sensible and latent heat fluxes after 48 hours. This work demonstrates the nonnegligible effect of including daily updates of sea-ice concentration in numerical weather forecasting and indicates the necessity of a fully coupled atmosphere-ocean-ice model in operational high-latitude southern hemisphere weather ...