Technical note: Intermittent reduction of the stratospheric ozone over northern Europe caused by a storm in the Atlantic Ocean

Mikhail Sofiev,Viktoria F Sofieva,Risto Hänninen,Rostislav Kouznetsov

doi:10.5194/acp-20-1839-2020

Abstract

Abstract. A 3 d episode of anomalously low ozone concentrations in the stratosphere over northern Europe occurred on 3–5 November 2018. A reduction of the total ozone column down to ∼ 200–210 Dobson units was predicted by the global forecasts of the System for Integrated modeLling of Atmospheric coMposition (SILAM) driven by the weather forecast of the Integrated Forecasting System (IFS) of the European Centre for Medium-Range Weather Forecasts (ECMWF). The reduction down to 210–215 DU was subsequently observed by satellite instruments, such as the Ozone Monitoring Instrument (OMI) and Ozone Mapping Profile Suite (OMPS). The episode was caused by an intrusion of tropospheric air, which was initially uplifted by a storm in the northern Atlantic, south-east of Greenland. Subsequent transport towards the east and further uplift over the Scandinavian ridge of this humid and low-ozone air brought it to ∼25 km altitude, causing ∼30 % reduction of the ozone layer thickness over northern Europe. The low-ozone air was further transported eastwards and diluted over Siberia, so that the ozone concentrations were restored a few days later. Comparison of the model predictions with OMI, OMPS, and MLS (Microwave Limb Sounder) satellites demonstrated the high accuracy of the 5 d forecast of the IFS–SILAM system: the ozone anomaly was predicted within ∼10 DU accuracy and positioned within a couple of hundreds of kilometres. This episode showed the importance of the stratospheric composition dynamics and the possibility of its short-term forecasting, including such rare events.

Highlights

Quick variations in the ozone abundance in the lower stratosphere and the upper troposphere are primarily associated with the stratosphere–troposphere exchange
According to the System for Integrated modeLling of Atmospheric coMposition (SILAM) forecasts, the episode was started at the beginning of November 2018 in the Atlantic Ocean south-east of Greenland by a strong storm (Figs. 1a and S1– S7 in the Supplement), which created a powerful updraught reaching up to nearly 15 km of altitude
An episode of a strong tropospheric intrusion into the UTLS and to the middle stratosphere was predicted by the SILAM model and subsequently observed by the ozone monitoring satellites at the beginning of November 2018

Summary

Introduction

Quick variations (hours to days) in the ozone abundance in the lower stratosphere and the upper troposphere are primarily associated with the stratosphere–troposphere exchange. Attention is usually paid to intrusions of the stratospheric air into the troposphere along the descending dry-intrusion air streams of the cyclonic structure (Ebel et al, 1991; Jaeglé et al, 2017; Reutter et al, 2015; Stohl, 2001, 2003). These intrusions are estimated to be responsible for 450–500 Tg of annual ozone import in the troposphere, which is about 10 % of the ozone chemical production in the troposphere (Edwards and Evans, 2017; Olsen et al, 2013; Roelofs and Lelieveld, 2000). For the stratosphere-to-troposphere (STT) intrusions, in particular, the fraction of streams reaching the middle troposphere is suggested to be just 15 % (Jaeglé et al, 2017)

Results

Discussion

Conclusion