Unusual stratospheric ozone anomalies observed in 22 years of measurements from Lauder, New Zealand

Abstract

Abstract. The Microwave Ozone Profiling Instrument (MOPI1) has provided ozone (O3) profiles for the Network for the Detection of Atmospheric Composition Change (NDACC) at Lauder, New Zealand, since 1992. We present the entire 22 year dataset and compare with satellite O3 observations. We will study in detail two particularly interesting variations in O3. The first is a large positive O3 anomaly which occurs in the mid-stratosphere at ~10–30 hPa in June 2001, and which is caused by an anticyclonic circulation that persists for several weeks over Lauder. We find that this O3 anomaly is associated with air with the highest June average tracer equivalent latitude (TrEL) over the 35 year period (1980–2014). A second, and longer-lived feature, is a positive O3 anomaly in the mid-stratosphere (~10 hPa) from mid-2009 until mid-2013. Coincident measurements from the Aura Microwave Limb Sounder (MLS) show that these high O3 mixing ratios are well correlated with high nitrous oxide (N2O) mixing ratios. This correlation suggests that the high O3 over this 4 year period is driven by unusual dynamics. The beginning of the high O3 and high N2O period at Lauder (and throughout this latitude band) occurs nearly simultaneously with a~sharp decrease in O3 and N2O at the equator, and the period ends nearly simultaneously with a~sharp increase in O3 and N2O at the equator.