A model study of the January 2006 low total ozone episode over Western Europe and comparison with ozone sonde data

Abstract

Abstract. Total column and stratospheric ozone levels at mid-latitudes often reveal strong fluctuations on time scales of days caused by dynamic processes. In some cases the total ozone column is distinctly reduced below climatological values. Here, a very low total ozone episode around 19 January 2006 over Western Europe is investigated when the observed total ozone column over Uccle (BE), measured by a Brewer spectrophotometer, reached a daily minimum of 200 DU, the lowest recorded value at this station. In order to investigate the mechanisms leading to the ozone minimum, the present study used data from (i) six ozone sounding stations in Western and Middle Europe, (ii) ECMWF meteorological fields, (iii) a simulation of the CLaMS model for January 2006, (iv) a multi-year run of the chemistry transport model KASIMA, and (v) a six-year run of the climate chemistry model ECHAM5/MESSy1. The ozone decrease at different heights was quantified and it was determined to what extent different transport mechanisms, and instantaneous, insitu chemical ozone depletion contributed to the event. All three models reproduced the evolution and formation of the event. The ozone column decrease between =300 and 750 K was strongest at Uccle (BE) and De Bilt (NL) with 108 and 103 DU, respectively, and somewhat lower at Hohenpeissenberg (DE), Payerne (CH), Prague (CZ) and Lerwick (UK) with 85, 84, 83 and 74 DU, respectively. This analysis demonstrated that mainly the displacement of the ozone depleted polar vortex contributed to the ozone column decrease. Advection of ozone-poor low-latitude air massesCorrespondence to: A. Mangold (alexander.mangold@oma.be) was important in the UTLS region. The vertical displacement of isentropes connected with divergence of air out of the column was found to be of minor importance compared to the horizontal transport processes. Severe low total ozone episodes seem to occur when the mentioned mechanisms are superimposed. Instantaneous, in-situ chemical ozone depletion accounted for only 2±1% of the overall total ozone decrease at the sounding stations.

An assessment of Ozone Mini-holes Representation in Reanalyses Over the Northern Hemisphere

“…These trajectories were taken from the MLS Lagrangian Trajectory Diagnostic dataset (Livesey et al, 2015), which is a set of 15-day forward and 15-day reverse trajectories launched from a curtain of points along the MLS track. These calculations are based on wind fields and diabatic heating rates taken from the MERRA-2 reanalysis and the advection calculations are based on the algorithm used by Manney et al (1994). As expected, the majority of the air parcels in the mid-stratosphere originate near the polar vortex.…”

“…As pointed out by Reed (1950), they result from a combination of uplift of air and horizontal advection. Assuming net divergence, local uplift of the air increases the amount of the column occupied by ozone-poor tropospheric air (e.g., Salby and Callaghan, 1993;Petzoldt et al, 1994;Teitelbaum et al, 1998;Hood et al, 2001;Canziani et al, 2002) while horizontal advection brings ozone-poor air into the column through poleward transport around the tropopause, through equatorward transport of polar air around the middle of the stratosphere, or through a combination of the two (e.g., Vaughan and Price, 1991;Orsolini et al, 1995;Peters et al, 1995;James et al, 2000;Allen and Nakamura, 2002;James and Peters, 2002;Mangold et al, 2009).…”