Seminars

Lecturer: Joël Arnault
Date: 2013-02-19 10:30
Place: Aniara

Dynamical influence of a mountain wave generated at the edge of the Antarctic Plateau near Troll Station: Radar observations and model analysis

A case-study of a mountain wave inducing a close-to-convective overturning layer, enhanced turbulence and oscillations of horizontal wind in the upper troposphere ? lower stratosphere has been observed with the Moveable Atmospheric Radar for Antarctica (MARA) at the Norwegian Troll Antarctic station during the period 20-22 July 2012. This situation is reproduced rather realistically, except for the turbulence, in a four-day Weather Research and Forecasting (WRF) model simulation using two-way-grid-nested outer and inner domains of horizontal size (south-north x east-west in km) 3600 x 9000 and 1800 x 2280, and horizontal resolutions 30 and 6 km, respectively, and a vertical resolution of about 300 m with a model top at 38 km. In the simulation the modelled mountain wave is stationary, partially breaks in the lower stratosphere in association with the generation of a secondary inertia-gravity wave, and partially breaks in the middle stratosphere in association with increased turbulence and the generation of a tertiary stationary gravity wave of smaller vertical wavelength. A budget analysis of potential temperature and horizontal wind components is carried out in the WRF simulation, and the results obtained are compared with those from a control simulation in which the gravity wave activity has been removed. A vertical-cross-section-analysis of the so-called differential budgets is used to study the link between the modelled mountain wave, convective overturning and the generation mechanism of a secondary inertia-gravity wave. A domain-averaged analysis of these differential budgets is finally used to quantify the dynamical impact of the modelled gravity wave activity on the inner-domain-averaged flow.

Created 2013-02-14 10:21:15 by Uwe Raffalski
Last changed 2013-02-14 21:17:14 by Uwe Raffalski