An Analysis of the Low-Level Wind Field Over the Ross Ice Shelf, Antarctica

Melissa A. Richards (Nigro)John J. Cassano

University of Colorado

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Agenda

• Components of the Low-Level Wind Field Over the Ross Ice Shelf

• Strong Wind Speeds Near the Dufek Coast & the Prince Olav Mountains

• Case Study – September 2009

• Conclusion & Future Work Sabrina AWSPhoto Courtesy of Shelley Knuth

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Components of the Low-Level Wind Field

Katabatic Winds

Figure from Parish and Bromwich (1987)Barrier Winds

Figure from Parish et al. (2006)

Synoptic Forcing

Average Wind Field

Role of local topography?

Dufek Coast & Prince Olav Mountains

Dufek Coast & Prince Olav Mountains

Previous studies– Seefeldt and Cassano [2008]

• Mountains protrude into low-level jet resulting in a tip jet

– Steinhoff et al. [2009] • Flow is primarily around the mountains not over resulting in a

“knob” flow

– Each study mentions the need for additional analysis of the dynamics in this region to determine the mechanisms responsible for the strong winds in this region

September 2009 Case Study

September 2009 Case Study

Synoptic Forcing – Over the RIS

BEFORE

AFTER

Barrier Winds

700 mb Winds SLP10 m Winds

Synoptic Forcing – Upper Level Ridge

BEFORE

AFTER

SLP 500 mb 300 mb

September 2009 Case Study

Conclusion & Future Steps

CONCLUSIONS:• The interaction of two or more forcing mechanisms can result in

areas of very strong winds• Forcing for barrier wind development not seen at the 10 meter

level, but evident at 700 mb where observations do not currently exist

• The forcing mechanisms throughout the jet are spatially different

FUTURE STEPS:• Understand the dynamics that cause the jet to accelerate in the

location of the Sabrina AWS• Determine how often these events occur and if the same forcing

mechanisms are present