The shallow katabatic flows over Dronning Maud Land, Antarctica 
Rostislav Kouznetsov, Priit Tisler, Timo Palo, Timo Vihma
 
The three-axes Doppler sodar Latan-3 was operated near the Finnish
Antarctic station Aboa in Dronning Maud Land (73°03'S, 13°25'W) in
austral summer 2010-2011. The measuring site is located at practically
flat slightly sloped (about 1%) surface of the glacier. The sodar was
operated in multiple frequency parallel mode with 20--800~meters
sounding range, 20 m vertical and 10 s temporal resolution. To reveal
the wind and temperature profiles below the sounding range as well as
turbulent fluxes at 2 and 10 meters, the data of 10-m meteorological
mast were used.
 
During the measurements the atmospheric boundary layer was most of the
time within the sounding range of the sodar. Despite a large variety of
observed sodar echo patterns and wind speed profiles,  several cases of
clear steady katabatic flows were observed. Practically all of them were
Easterly, whereas the uphill direction is Southern. The thickness of the
katabatic flow varied from few tens to several hundreds of meters, the
wind speed maximum could be as low as 5~meters.  Thin katabatic flows
had lower wind speed and much stronger temperature gradient (up to
1~K/m), but smaller surface heat flux than the thicker ones.
 
Such situations pose a major challenge for meteorological models, 
since the surface layer in these cases appears just within the lowest
meters.