A new look at Southeast Greenland barrier winds and katabatic flow

Southern Greenland is characterized by a number of high speed low-level weather systems that are all the result of the interaction of the topography of the Greenland with passing extra-tropical cyclones. These systems include westerly and easterly tip jets that form near Cape Farewell, Greenland's southernmost point, as well as barrier winds and katabatic flow that occur along its southeast coast. The high winds associated with these events play an important role in the regional meteorology and climate. In addition, the air-sea fluxes of heat, momentum and moisture associated with these orographic jets impact the surface oceanography of the region, including fiord-ocean circulations, as well as contributing to the forcing of the lower limb of the Atlantic Meridional Overturning Circulation. Atmospheric reanalyses have proven to be important tools in furthering our understanding of these orographic winds and their role in the climate system. However, their horizontal scale is on the order of 200-400 km and there is a concern that important details as to their fine-scale structure may be missed by current global reanalyses products. In this article, we compare and contrast the representation of barrier winds and katabatic flow in the ECMWF's Interim Reanalysis (ERA-I), a typical latest generation global reanalysis, and the Interim Arctic System Reanalysis (ASR-I), a higher horizontal resolution regional reanalysis of the Arctic region. As we shall see, the enhanced spatial resolution of the ASR-I allows for a more detailed view of both barrier winds and katabatic flow that occur along the southeast coast of Greenland. There are also significant differences in the character of high wind speed events in the two reanalyses, both over the Greenland Ice Sheet as well as the coastal sea ice, that will require further study to understand.