Fine-scale model simulation of gravity waves generated by Basen nunatak in Antarctica

摘要

Gravity waves over a small nunatak in Dronning Maud Land, Antarctica, were simulated applying the mesoscale model Weather Research and Forecasting (WRF). Most model experiments were made using three nested domains with 0.9 km horizontal resolution in the finest grid. The model results were validated against observations from a vertically pointing 54.5 MHz VHF radar, which provided profiles of the vertical and horizontal wind components over the nunatak. The WRF model generated gravity waves in the periods when these were observed. The modelled wave characteristics were qualitatively similar to the observed ones, although quantitative differences existed. The gravity wave had a typical vertical wave length of 3-4 km, and a maximum amplitude of 1 m s~(-1) in the vertical velocity field. The amplitude was largest at altitude of 2.0-3.5 km. The wave was strongest during nighttime, when the surface sensible heat flux was downwards. The evolution of vertical profiles of the observed rms fluctuation of vertical wind velocity and the modelled bulk Richardson number resembled each other. Gravity waves may affect the safety of aircraft landing and take-off on the lee side of the nunatak.