UK Met Office Unified Model high-resolution simulations of an Antarctic strong wind event

Much of the Antarctic coast is susceptible to severe and hazardous strong wind events (SWEs) associated with the enhancement of strong katabatic flow by the synoptic situation. The ability of models to simulate such events is challenging due to the complex dynamics and the significant influence of complex surface features (e.g., generation of gravity waves). In this study, a SWE which occurred at Mawson, East Antarctica on 25 July 2004 involving a hurricane force wind speed of ~39 m/s is simulated by the UK Met Office Unified Model (MetUM) (version 7.6) at three different horizontal resolutions of 12, 4, and 1.5 km. It is apparent that all the models: i) capture the qualitative evolution of the SWE suggesting that they are resolving the important forcing mechanisms, ii) capture the weaker wind speeds associated with the onset and cessation of the SWE, and iii) underestimate the peak wind speed. The strength of the underestimate is dependent on horizontal resolution, with the 4 and 1.5-km (12-km) models underforecasting the peak wind speed by around 15% (36%). Additional sensitivity experiments and diagnostics are presented to improve understanding of the processes responsible for the SWE and to identify shortcomings in the model that require improvements in the future.