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The atmospheric boundary layer and surface conditions during katabatic wind events over the Terra Nova Bay Polynya.
  • Marta Aleksandra Wenta,
  • John J. Cassano
Marta Aleksandra Wenta
University of Gdansk

Corresponding Author:martawenta@gmail.com

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John J. Cassano
University of Colorado Boulder
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Off the coast of Victoria Land, Antarctic an area of open water - the Terra Nova Bay Polynya (TNBP)- persists throughout the austral winter. The primary force driving the development of this almost ice-free stretch of water are extreme katabatic winds flowing down the slopes of Transantarctic Mountains. The surface-atmosphere coupling and ABL transformation during the katabatic flow between 18-25 September 2012 in Terra Nova Bay are studied, using observations from Aerosonde unmanned aircraft system (UAS) observations, numerical modeling results and Antarctic Weather Station (AWS) measurements. Our analysis demonstrates that the intensity and persistence of katabatic winds is governed by sea level pressure (SLP) changes in the region. Whereas the duration and intensity of the flow, determines the polynya extent. When cold, dry air brought with the winds interacts with relatively warm surface of the polynya the convection starts to develop and overcomes the previously stable atmosphere. In general, the intensity of the flow, surface conditions in the bay and regional SLP fluctuations are all interconnected and together modify local atmospheric and surface conditions. The importance of valid forecast of katabatic events for Antarctic aircraft operations is unambiguous. The Antarctic Mesoscale Prediction System (AMPS) performs this task well, but due to exaggerated sea ice concentrations (SIC) incorrectly represents vertical ABL properties and air mass modification over the TNBP. Altogether, this research provides a unique description of TNBP development and its interactions with the atmosphere and katabatic winds, thus enhancing our understanding of the complex processes taking place in this region.