Response of trace gases to the disrupted 2015–2016 quasi-biennial oscillation

Abstract

Abstract. The quasi-biennial oscillation (QBO) is a quasiperiodic alternation between easterly and westerly zonal winds in the tropical stratosphere, propagating downward from the middle stratosphere to the tropopause with a period that varies from 24 to 32 months ( ∼ 28 months on average). The QBO wind oscillations affect the distribution of chemical constituents, such as ozone (O 3 ), water vapor (H 2 O), nitrous oxide (N 2 O), and hydrochloric acid (HCl), through the QBO-induced meridional circulation. In the 2015-2016 winter, radiosonde observations revealed an anomaly in the downward propagation of the westerly phase, which was disrupted by the upward displacement of the westerly phase from ∼ 30 hPa up to 15 hPa and the sudden appearance of easterlies at 40 hPa. Such a disruption is unprecedented in the observational record from 1953 to the present. In this study we show the response of trace gases to this QBO disruption using O 3 , HCl, H 2 O, and temperature from the Aura Microwave Limb Sounder (MLS) and total ozone measurements from the Solar Backscatter Ultraviolet (SBUV) Merged Ozone Data Set (MOD). Results reveal the development of positive anomalies in stratospheric equatorial O 3 and HCl over ∼ 50-30 hPa in May-September of 2016 and a substantial decrease in O 3 in the subtropics of both hemispheres. The SBUV observations show near-record low levels of column ozone in the subtropics in 2016, resulting in an increase in the surface UV index during northern summer. Furthermore, cold temperature anomalies near the tropical tropopause result in a global decrease in stratospheric water vapor.

Validation of ozone profile retrievals derived from the OMPS LP version 2.5 algorithm against correlative satellite measurements

“…As a result trace gases in the tropical stratosphere responded to 20 this disruption. Tweedy et al (2017) demonstrated that during the 2016 boreal summer, total ozone was lower in the extratropics than during previous QBO cycles because of the change in the circulation caused by this disruption. Figure 15 shows the ozone response to the disrupted QBO as measured by OMPS LP and Aura MLS.…”

“…In July 2014 version 15 2 of the LP ozone profile dataset was released. Here we present a new version 2.5 of the LP ozone data that have been publically released in July 2017 (Kramarova et al, 2017). Both datasets (version 2 and version 2.5) have been produced using a modified version of the OMPS LP retrieval algorithm.…”

“…Harris et al, 2014). Unexpected variations in the atmospheric circulation, not captured by models, such as the recent disruption of the quasi-biennial oscillation (Newman et al, 2016, Tweedy et al, 2017, contribute to additional noise in the trend estimates and emphasize the continued importance of high quality ozone measurements.…”

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

“…This means that a trend of 1 % decade −1 could be observed after 20 years of observations following the ODS peak. The below-average annual mean NH total ozone in 2016 is linked to the severe Arctic ozone depletion in the same year (Manney and Lawrence, 2016) and related to the anomalous QBOinduced meridional circulation changes (Osprey et al, 2016;Tweedy et al, 2017). This resulted in a drop of the 1997-2016 NH ozone trend down to +0.4 % decade −1 (compared to +0.6 % decade −1 ending in 2015).…”

State of the Climate in 2016

“…The QBO is a periodic change of stratospheric winds in the lower to middle tropical stratosphere that affects the meridional (Brewer-Dobson) circulation and modulates high latitude ozone and the strength of the polar vortices (e.g., Strahan et al 2015). In the 2015/16 boreal winter, radiosonde temperature observations revealed an unprecedented disruption in the downward propagation of the QBO westerly phase (Newman et al 2016) that modified circulation and substantially impacted tropical and extratropical ozone (Tweedy et al 2017). In Fig.…”