Influence of the Arctic Oscillation on the Vertical Distribution of Wintertime Ozone in the Stratosphere and Upper Troposphere over the Northern Hemisphere

Abstract

The influence of the Arctic Oscillation (AO) on the vertical distribution of stratospheric ozone in the Northern Hemisphere in winter is analyzed using observations and an offline chemical transport model. Positive ozone anomalies are found at low latitudes (08-308N) and there are three negative anomaly centers in the northern midand high latitudes during positive AO phases. The negative anomalies are located in the Arctic middle stratosphere (;30 hPa; 708-908N), Arctic upper troposphere-lower stratosphere (UTLS; 150-300 hPa, 708-908N), and midlatitude UTLS (70-300 hPa, 308-608N). Further analysis shows that anomalous dynamical transport related to AO variability primarily controls these ozone changes. During positive AO events, positive ozone anomalies between 08 and 308N at 50-150 hPa are related to the weakened meridional transport of the Brewer-Dobson circulation (BDC) and enhanced eddy transport. The negative ozone anomalies in the Arctic middle stratosphere are also caused by the weakened BDC, while the negative ozone anomalies in the Arctic UTLS are caused by the increased tropopause height, weakened BDC vertical transport, weaker exchange between the midlatitudes and the Arctic, and enhanced ozone depletion via heterogeneous chemistry. The negative ozone anomalies in the midlatitude UTLS are mainly due to enhanced eddy transport from the midlatitudes to the latitudes equatorward of 308N, while the transport of ozone-poor air from the Arctic to the midlatitudes makes a minor contribution. Interpreting AO-related variability of stratospheric ozone, especially in the UTLS, would be helpful for the prediction of tropospheric ozone variability caused by the AO.

Total ozone trends from 1979 to 2016 derived from five merged observational datasets – the emergence into ozone recovery

“…Apart from the year-to-year variability, the AO index increased throughout the 1980s along with the EESC (ODSs) as shown in Fig. 1 in Weber et al (2011) (see also Zhang et al, 2017). The very high total ozone observed at NH middle latitudes in 2010 (Fig.…”

Mechanisms Governing Interannual Variability of Stratosphere‐to‐Troposphere Ozone Transport

“…These complications notwithstanding, Kiesewetter et al (2010) provided evidence in support of the NAM downward transport connection on an episodic basis whereby strong positive/negative NAM anomalies were followed by significant downward propagating negative/positive ozone anomalies (see also, Zhang et al, 2017). If each winter season is assumed to be made up of several episodic events, then years when the NAM is weak (or strong)-in a season-long integrated sense-should be associated with a higher (or lower) than average accumulation of ozone in the March lower stratospheric reservoir; this in turn may translate to higher or lower ozone IntrMass.…”

“…These two mechanisms provide the means for climate variability on interannual to decadal timescales-in both the stratosphere and troposphere-to modulate STT of ozone. For example, changes in the strength of stratospheric planetary wave driving, which modulates the BDC and thus extratropical ozone abundances (StratVarO 3 ), can be influenced by major modes of extratropical climate variability including ENSO, the stratospheric portion of the Northern Annular Mode (NAM), and the quasi-biennial oscillation (QBO) (e.g., García-Herrera et al, 2006;Hsu & Prather, 2009;Kiesewetter et al, 2010;Zhang et al, 2017). Likewise, ENSO-though typically weak during spring and summer-and the UTLS portion of the NAM are associated with shifts in Pacific wave breaking patterns and thus STT of ozone via JetVar.…”

Total ozone trends from 1979 to 2016 derived from five merged observational datasets – the emergence into ozone recovery

“…Apart from the year-to-year variability the AO index increased throughout the 1980s along with the EESC (ODS) as shown in Fig. 1 in Weber et al (2011) (see also Zhang et al (2017)). The very high total ozone observed at NH middle latitudes in 2010 (Fig.…”