A Dynamical Explanation of the Topographically Bound Easterly Low‐Level Jet Surrounding Antarctica

• Published in: Journal of geophysical research. Atmospheres 2017-12, Vol.122 (23), p.12,635-12,652
• Main Authors: Fulton, Scott R., Schubert, Wayne H., Chen, Zhengqing, Ciesielski, Paul E.
• Format: Article
• Language: English
• Subjects: Antarctic low‐level jet; balanced dynamical model; Banks (topography); Coastal zone; Cold pressing; Cooling; Easterlies; Geophysics; Katabatic winds; Levels; Low-level jets; Lower atmosphere; Mathematical models; Meridional circulation; Plateaus; Potential vorticity; potential vorticity inversion; Pressure distribution; Radiative cooling; Slope; Spherical coordinates; Temperature; topographically bound flow; Topography; Topography (geology); Vorticity; Weather forecasting; Wind; Wind patterns; Winds
• ISSN: 2169-897X; 2169-8996
• DOI: 10.1002/2017JD027192

This study investigates the topographically bound easterly low‐level jet surrounding Antarctica. This jet is modeled as a balanced flow that satisfies the potential vorticity invertibility principle, based on local linear balance in spherical coordinates and expressed in isentropic coordinates. In this way, this easterly low‐level jet is shown to be the balanced flow associated with the topography of the Antarctic plateau, moderated by a shallow potential vorticity anomaly atop the plateau produced by radiative cooling. The dynamical connection of the jet with katabatic winds can be understood through the meridional circulation equation. Model results based on the simple theoretical arguments developed here are found to be consistent with high‐resolution reanalysis data from the European Centre for Medium‐Range Weather Forecasts for the 2008–2010 period. Plain Language Summary This study investigates the persistent strong easterly wind (jet) that flows in the lower atmosphere along the eastern coastal region of Antarctica. It is shown that this low‐level jet may be explained as a balanced flow—resulting from a dynamical balance between wind and pressure fields—associated with the cold, high Antarctic plateau. The explanation of this jet may lead to a better understanding of wind patterns over Antarctica and their relation to the topography of the continent. Key Points Balanced Antarctic circumpolar winds are modeled by inversion of potential vorticity The easterly low‐level jet is due to topography and moderated by radiative cooling Dynamical connection of jet with katabatic winds is explained through the meridional circulation