INTERACTION OF KATABATIC FLOW WITH LOCAL THERMAL EFFECTS IN A COASTALREGION OF ADELIE LAND, EAST ANTARCTICA

Katabatic flows largely dominate the climate of the Adelie Land coasta l region. A detailed climatological data analysis of Dumont d'Urville has been conducted. Results of this study support the idea that kataba tic flow can be locally enhanced by the diurnal cycle of solar insolat ion and the temperature contrast between the continent and the ocean. The interaction between katabatic wind and local thermal effects is ex pressed in terms of scale analysis. Except for surface stress, all ter ms in the momentum equation for a katabatic flow in a coastal region o f Antarctica can reach the same order of magnitude. The local circulat ion then is the result of a relatively tenuous force balance which can be disrupted even by a weak perturbation of any term. To estimate the effect of the temperature contrast between the ocean and the continen t on the katabatic flow, two numerical experiments have been conducted . The simulations consider an ocean free of sea ice representative of the summer months, and another winter case with the ocean covered by t hick sea ice. These simulations show that with the ocean free of sea i ce, the katabatic flows extend only a limited distance over the open o cean during the day due to the local thermal effects. With the ocean c overed by sea ice, the katabatic winds are not constrained and extend a considerable distance offshore.