Fig. 1.
(a) Terrain elevation of Antarctica. The black square shows the location of the WRF outer domain. The altitude is in metres above mean sea level with the scale given by the coloured bar on the right-side of the figure. (b) As in (a), except for the WRF outer domain and for the inner domain delimited by the black inner square, in the case of the WRF simulation with orography. The curved line on the north-west corner corresponds to the coast, the straight line (A–B) gives the location of the vertical cross-sections in Figs. 5, 9, 10 and the position of the Aboa/Wasa station at the Basen nunatak is also indicated by a cross on this line. The mountainous area crossed by A–B is the Vestfjella Mountains.
Fig. 2.
(a–c) Time-height diagram of vertical velocity (colours) and horizontal winds (arrows) in ms−1, from MARA observations. The horizontal axis gives the time in days (a: 5–23 December 2007, b: 24 December 2007–11 January 2008, c: 12–31 January 2008) and the vertical axis gives the height in m. The vertical velocity scale is given by the coloured bar on the right of each panel. The wind scale is given by the arrow above this coloured bar. (d–f) As in (a–c), except from the WRF inner model experiment with orography.
Table 1. Occurrence of tropospheric gravity waves associated with low-level winds having a northeasterly component, as inferred with MARA data during the period from 5 December 2007 to 31 January 2008. The first column indicates the days when the gravity wave was detected, the second column gives the time duration of the event in hours, the third column gives the highest height reached by the low-level winds having a northeasterly component and the fourth column the highest height reached by the gravity wave. Gravity waves reaching tropopause heights are in bold characters
Fig. 3.
As in Fig. 2, except for the buoyancy frequency (s−1).
Fig. 4.
Result of WRF modelling experiment with orography showing the horizontal cross-section at 6000 m altitude of vertical velocity (colour) and horizontal winds (arrows) in ms−1, on 10 December 2007 at 21:00 UTC. The vertical velocity scale is given by the coloured bar on the right side of the panel. The wind scale is given by the arrow on the bottom right corner of the panel. (b) As in (a), except at 16 000 m altitude.
Fig. 5.
(a) Result of the WRF modelling experiment with orography showing the vertical cross-section from the inner model on 10 December 2007 at 21:00 UTC at the location indicated by the line (A–B) in Figs. 1 and 4, for the vertical velocity (colour) in ms−1, the wind projected on the plane of the cross-section (arrows) in ms−1 and the isentropes (black contours) in K. The horizontal axis gives the horizontal coordinate in (latitude, longitude) and the vertical axis on the left side (right side) gives the altitude in m (the potential temperature in K). The profile of the Vestfjella Mountains is shaded in black, with the Basen nunatak at the radar location indicated by the black vertical line. The vertical velocity scale is given by the coloured bar on the right side of the panel. The projected wind takes into account the vertical velocity and the scale is given by the arrows on the top right corner of the panel. (b) As in (a), except for the buoyancy frequency in s−1. (c) As in (a), except for the bulk Richardson number. (d) As in (a), except for the horizontal wind orthogonal to the plane of the vertical cross-section in ms−1.
Fig. 6.
(a) Time-height diagram of the difference between the vertical velocities (ms−1) from the WRF model experiments with and without orography, averaged horizontally in the inner domain at a time resolution of 1 h. The horizontal axis gives the time in days from 5 December 2007 to 31 January 2008 and the vertical axis gives the height in m. The vertical velocity scale is given by the coloured bar on the right side of the panel. (b) As in (b), except for the horizontal divergence in s−1. (c) As in (a), except for the difference between geostrophic and vertical relative vorticities in s−1.
Fig. 7.
(a) As in Fig. 6, except for KH (J kg−1) from the WRF simulation with orography and with a time resolution of 24 h for the input data. (b) As in (a), except for the difference of KH between the two simulations with and without orography.
Fig. 8.
As in Fig. 6, except for the difference of the terms (in W kg−1) of the budget of KH between the two simulations with and without orography and with a time resolution of 24 h for the input data: (a) tendency, (b) sum of the source terms, (c) horizontal advection. (d) vertical advection, (e) horizontal work of pressure forces, (f) frictional dissipation.
Fig. 9.
As in Fig. 5, except for the difference of KH between the two simulations with and without orography in J kg−1, computed on 10 December 2007 21:00 UTC.
Fig. 10.
As in Fig. 5, except for the difference of the terms of the budget of KH between the two simulations with and without orography in W kg−1, computed on 10 December 2007 between 20:00 and 22:00 UTC.
