The structure and evolution of the stratospheric vortex in response to natural forcings

Peer Reviewed

Mitchell DM, Gray LJ, & Charlton-Perez AJ

Journal of Geophysical Research: Atmospheres (1984–2012) 116, Issue D15, pages D15110, 2011, 10.1029/2011JD015788.

The structure and evolution of the Arctic stratospheric polar vortex is assessed during opposing phases of, primarily, the El Niño–Southern Oscillation (ENSO) and the Quasi-Biennial Oscillation (QBO), but the 11 year solar cycle and winters following large volcanic eruptions are also examined. The analysis is performed by taking 2-D moments of vortex potential vorticity (PV) fields which allow the area and centroid of the vortex to be calculated throughout the ERA-40 reanalysis data set (1958–2002). Composites of these diagnostics for the different phases of the natural forcings are then considered. Statistically significant results are found regarding the structure and evolution of the vortex during, in particular, the ENSO and QBO phases. When compared with the more traditional zonal mean zonal wind diagnostic at 60°N, the moment-based diagnostics are far more robust and contain more information regarding the state of the vortex. The study details, for the first time, a comprehensive sequence of events which map the evolution of the vortex during each of the forcings throughout an extended winter period.

Keywords: El Niño–Southern Oscillation, ENSO, Quasi-Biennial Oscillation, QBO, Natural forcings, Polar vortex, Solar cycle, Stratosphere
Categories: Arctic, Natural Science