Topographically forced mesocyclones in the Ross Sea region of Antarctica 1988

The complex Antarctic topography of the coastal regions can play an important role in mesocyclogenesis. In the Ross Sea region the topographic structure along the coast leads to a significant channeling of the katabatic boundary layer winds. In connection with additional synoptic forcing, the vertical stretching of the converging flow leads to a production of cyclonic vorticity. Besides this stretching mechanism, katabatic winds can have a second impact on the generation of  MCs by transporting cold air into the coastal areas and thereby enhancing the low-level baroclinicity. Climatologies mainly based on satellite imagery show that MCs occur frequently in the Ross Sea region of Antarctica (Carrasco and Bromwich 1994). The case of 18 February 1988 is a good example of the interaction of katabatic winds and MCs in the areas of Terra Nova Bay and McMurdo, and have been studied using observations by Bromwich (1991) and Carrasco and Bromwich  (1993, 1995) and by Heinemann and Klein (2001) using mesoscale model simulations.

Bromwich, D. H., 1991: Mesoscale cyclogenesis over the southwestern Ross Sea linked to strong katabatic winds. Mon. Wea. Rev. 119, 1736-1752.
Carrasco, J. F., and D. H. Bromwich, 1994: Climatological aspects of mesoscale cyclogenesis over the Ross Sea and Ross Ice Shelf regions of Antarctica. Mon. Wea.  Rev., 122, 2405-2425.
Carrasco, J. F., Bromwich, D. H., 1995: A Midtropospheric Subsynoptic-scale Vortex that developed over the Ross Sea and Ross Ice Shelf of Antarctica. Antarctic Sci., 7, 199-210.
Heinemann, G., Klein, T., 2001: Simulations of topographically forced mesocyclones in the Weddell Sea and the Ross Sea region of Antarctica. Submitted to Mon. Wea. Rev.

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Copyright by Günther Heinemann.

AVHRR channel 4 image (brightness temperature scale in K) for AVHRR infrared satellite image (NOAA, channel 4, grey scale in K) for 1300 UTC 18 February 1988. M1 indicates a MC. The Ross Ice Shelf (RIS) and Ross Island (RI) are indicated.
Wind vectors, potential temperature (dashed isolines every 2K) and relative humidity (shaded if larger than 90\%) at 925 hPa after 18h of NORLAM integration (valid at 1800UTC 18 February 1988). M1 indicates the simulated MC near Terra Nova Bay (Ter). The topography is shown by full lines (isolines every 500m).