Tracer transport during the Arctic stratospheric final warming based on a 33-year (1979-2011) tracer equivalent latitude simulation

Abstract

During the 2011 stratospheric final warming (SFW), a large anticyclone rapidly encompassed the pole, displacing the polar vortex and establishing strong summer easterlies. Tracer Equivalent Latitude (TrEL) maps indicate low latitude air was transported by the anticyclone into the summer polar vortex. MLS nitrous oxide was anomalously high throughout the following summer, confirming the TrEL results. A 33-year (1979-2011) TrEL simulation at 850K potential temperature reveals a number of similar low-TrEL events, which are often, but not always, associated with Frozen-In Anticyclone (FrIAC) formation. The summertime TrEL values are highly correlated with zonal wind speed in the polar stratosphere following the SFW, suggesting that strong post-SFW circulation favors polar trapping of low-TrEL air. The 2011 event, classified as a large-scale FrIAC, was unusual in having the lowest TrEL values and the strongest easterly vortex within the past three decades. copyright 2012 by the American Geophysical Union.