92nd American Meteorological Society Annual Meeting (January 22-26, 2012)

Tuesday, 24 January 2012: 9:15 AM
Stratospheric Circulation Associated with Negative Arctic Oscillation Transitions
Room 345 (New Orleans Convention Center )
Jason C. Shafer, Lyndon State College, Lyndonville, VT; and P. G. Hogan

This presentation will show stratospheric circulation patterns associated with negative Arctic Oscillation transitions. A total of 20 major negative AO transitions were identified, and the precursor and concomitant stratospheric circulation patterns were analyzed. Not surprisingly, after major negative AO transitions, there is an increased risk of cold temperatures across much of the U.S., peaking 15- 25 days after the composite transition.

Results show robust stratosphere circulations associated with most –AO transitions. For example, more than half of the events were led by sudden stratospheric warmings, which were associated with splitting or displacement of the polar vortex. Around the time of the –AO transition, a consistent stratospheric circulation pattern emerged, with positive 10-hPa height anomalies over polar regions in the western hemisphere, and negative 10-hPa height anomalies in the north-central Canada.

Events with a leading SSW may precondition the tropospheric response favoring a negative AO state. In the troposphere, a link between North Pacific and North Atlantic high latitude ridging appears, with many events lead by a North Pacific ridge and then followed by a North Atlantic ridge as the AO transitions negative. Implications for subseasonal temperature prediction will be discussed.

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