Abstract : L.3
High resolution simulations of lee wave events during T-REX using the Met Office Unified Model

Peter Sheridan, Simon Vosper
Met Office

During the recent T-REX field campaign in the Sierra Nevada mountains, USA, mountain wave/rotor systems of varying intensity occurred over Owens valley, which was the location of the majority of field instrumentation. The Met Office Unified Model (UM) has been used in a configuration driven at the coarse level by the global forecast run, and nested down to an inner domain of grid spacing 333 m, in order to model events during several T-REX IOPs. The model results have been compared with measurements of vertical motion obtained using the FAAM BAe 146 aircraft. In all cases a realistic simulated wave field was produced, with amplitude similar to that measured in each IOP, and providing insight into the large scale flow within and above Owens valley. In most cases, comparisons with the aircraft data indicate successful reproduction of the vertical structure of the wave field by the model also. Meanwhile, in some cases, the UM does not capture the vertical wave structure accurately; the horizontal phase of the lee waves is poorly predicted.

In this paper, the use of different model configurations will be examined as a means of elucidating the reasons for such inaccuracies, and to improve the agreement between the measured and simulated fields.