Idealized simulations of the Antarctic katabatic wind system with a three‐dimensional mesoscale model

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Abstract
The katabatic wind system represents a key factor for the near‐surface wind field of the Antarctic region. Idealized simulations with a three‐dimensional mesoscale model are performed to investigate the development of the Antarctic katabatic wind system and its sensitivity to physical boundary conditions, in particular channeling effects and the thermodynamic forcing close to the coastline. The simulated cases represent wintertime cases with complete sea ice coverage and no sea ice, as well as a realistic summertime situation. For the wintertime situations a large impact of the presence of open water on the three‐dimensional structure of the wind field close to the coast can be shown, whereas the effects on the katabatic wind over the continent are relatively small. Near‐surface wind speeds over the continental slope for the summertime case have strengths comparable to those of the wintertime cases but reveal a distinct daily cycle due to the daily course of the radiation fluxes. The formation of shallow mesoscale circulations is simulated after 2–4 days of simulation in ice‐free coastal areas. In these regions, low‐level convergence, diabatic heating, and the cold air advection associated with the katabatic flow leads to low‐level baroclinicity and cyclonic vorticity production.