The influence of orography and cloud amount on the flow dynamics close to Ny-Ålesund, Svalbard

Complex interactions exist in the Arctic region between atmosphere, ocean and sea ice inducing many processes of forcing and feedback associated in coastal regions with orography and cloud cover. From March 16 to September 16, 1998 a SODAR (SOund Detection and Ranging) was operated in a typical fjord region of Svalbard (Kongsfjord, Ny-Ålesund) which is characterised by a valley of ~10 km width surrounded by complex topography and glaciers. Wind velocity vertical profiles obtained with a high temporal and spatial resolution are used to study the Planetary Boundary Layer (PBL) structure. These measurements started as part of the Arctic Radiation and Turbulence Interaction STudy (ARTIST) and were continued later to study the PBL seasonal variability. The presented results mainly show the dependence of the flow regimes in the fjord on the geostrophic forcing (estimated from radio soundings) and typical interactions with clouds. In general we found three different flow regimes: one dominated from the geostrophic flow, the second one by the katabatic flow and the third one by the sea breeze. The first one occurs for strong geostrophic winds, which is typical of the springtime and then is often connected with katabatic flows. The third one is mainly found for light wind conditions in summer. A correlation between cloud cover, surface temperature and wind speed has been observed .