ENSO influences on Southern Hemisphere column ozone during the winter to spring transition

Abstract

This study investigates how the El Nino Southern Oscillation (ENSO) modulates the distribution of column ozone during the Southern Hemisphere (SH) winter to spring transition, when a zonal asymmetry in column ozone develops near 55°S, with a maximum south of Australia. ENSO differences in column ozone and planetary wave structure are explored for the average of seven El Nino (EN) versus six La Nina (LN) events during 1982–2004. A westward shift in convection during LN corresponds to a 30–50° westward shift of SH planetary wave and column ozone patterns. The extratropical lower stratospheric temperature anomalies are inversely correlated with tropical anomalies in similar longitude bands and are highly correlated with local column ozone anomalies. The tropical signal is communicated to higher latitudes by modulating subtropical anticyclones, with distinctive responses for EN and LN years for each month. During August and EN a subtropical anticyclone extends from South America to South Africa, and the wave one asymmetry of the Antarctic vortex is more pronounced and shifted eastward, along with column ozone. In September and EN a strong anticyclone exists over South Africa, with a corresponding cold, ozone‐poor anomaly in the stratosphere, diminishing the western edge of the ozone maximum. In October and LN a strong anticyclone exists over Australia, with an amplified trough on its poleward flank. This trough is overlain by an ozone‐rich warm anomaly, which expands the western edge of the ozone maximum, and the polar vortex asymmetry is amplified and rotated westward.