Low level wind and coastal Terra Nova Bay polynya:A study by Eta model simulations.

• Main Authors: MORELLI, Sandra, G. CASINI
• Other Authors: Morelli, Sandra, G., Casini
• Format: Conference Object
• Language: English
• Published: M. Colacino and C. Rafanelli. Società italiana di Fisica. 2009
• Subjects: Numerical model; katabatic wind; polynya; Antarctic; Terra Nova Bay; Eta; Antarc*; Sea ice
• Online Access: http://hdl.handle.net/11380/614936

The study focuses on a real event of katabatic wind and polynya at Terra Nova Bay (TNB). The katabatic winds and the impact of an open polynya on their intensity are simulated by a numerical atmospheric model. The event was selected as satellite images of September 2003 displaying a fluctuating TNB polynya, in particular on 16 September, the area of open water was of about 3100 km2. Simulations of the meteorological conditions of 15-16-17 September were carried on with the limited area Eta model, which is a three-dimensional, primitive equation, grid-point model. It is one of the mesoscale numerical weather prediction models operational at the National Centers for Environmental Prediction of the U.S. National Weather Service. The Eta model is coupled with a land surface model derived from the Oregon State University model and it is able to perform hydrostatic and non-hydrostatic runs. Further, terrain following or quasi-horizontal coordinates can be selected. Eta has been used for applications at mid-latitudes and, in an older version, for the study of Antarctic summer conditions. Eta runs were performed, both including the sea ice cover in the TNB area and a polynya of realistic extension, as shown from the satellite images in order to get an insight into the sensitivity of the katabatic wind to the presence of a polynya of realistic extension. The results show the strong effect of the polynya, included in the initialization of model simulations: the low level katabatic wind is intensified from the presence of the sea ice free area.The simulations were carried on using terrain following coordinates with 45 layers from sea surface to 25 hPa, with higher resolution near the bottom of the domain. Horizontal resolution was 0.05×0.05 transformed degrees (about 8 Km × 8 Km as approximate distance between two mass points on the semi-staggered Arakawa E grid). ECMWF and NCEP data provided initial and boundary conditions.Numerical simulations and results are presented and discussed.