Foehn winds in the McMurdo Dry Valleys, Antarctica: the origin of extreme warming events

Foehn winds resulting from topographic modification of airflow in the lee of mountain barriers are fre-quently experienced in the McMurdo Dry Valleys (MDVs) of Antarctica. Strong foehn winds in the MDVs cause dramatic warming at onset and have significant effects on landscape forming processes; howe...

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Bibliographic Details
Main Authors: Johanna C. Speirs, Daniel F. Steinhoff, Hamish A. Mcgowan, David H. Bromwich, Andrew J. Monaghan
Other Authors: The Pennsylvania State University CiteSeerX Archives
Format: Text
Language:English
Published: 2010
Subjects:
Antarctic
Byrd
Marie Byrd Land
McMurdo Dry Valleys
Polar Plateau
Ross Sea
The Antarctic
Antarc*
Antarctica
Online Access:http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.669.3089
http://polarmet.osu.edu/PMG_publications/speirs_steinhoff_jc_2010.pdf
Description
Summary:Foehn winds resulting from topographic modification of airflow in the lee of mountain barriers are fre-quently experienced in the McMurdo Dry Valleys (MDVs) of Antarctica. Strong foehn winds in the MDVs cause dramatic warming at onset and have significant effects on landscape forming processes; however, no detailed scientific investigation of foehn in the MDVs has been conducted. As a result, they are often mis-interpreted as adiabatically warmed katabatic winds draining from the polar plateau. Herein observations from surface weather stations and numerical model output from the Antarctic Mesoscale Prediction System (AMPS) during foehn events in the MDVs are presented. Results show that foehn winds in the MDVs are caused by topographic modification of south-southwesterly airflow, which is channeled into the valleys from higher levels. Modeling of a winter foehn event identifies mountain wave activity similar to that associated with midlatitude foehn winds. These events are found to be caused by strong pressure gradients over the mountain ranges of the MDVs related to synoptic-scale cyclones positioned off the coast of Marie Byrd Land. Analysis of meteorological records for 2006 and 2007 finds an increase of 10 % in the frequency of foehn events in 2007 compared to 2006, which corresponds to stronger pressure gradients in the Ross Sea region. It is postulated that the intra- and interannual frequency and intensity of foehn events in the MDVs may therefore

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