Antarctic ozone variability inside the polar vortex estimated from balloon measurements

Abstract

Abstract. Thirteen years of ozone soundings at the Antarctic Belgrano II station (78 • S, 34.6 • W) have been analysed to establish a climatology of stratospheric ozone and temperature over the area. The station is inside the polar vortex during the period of development of chemical ozone depletion. Weekly periodic profiles provide a suitable database for seasonal characterization of the evolution of stratospheric ozone, especially valuable during wintertime, when satellites and ground-based instruments based on solar radiation are not available. The work is focused on ozone loss rate variability (August-October) and its recovery (NovemberDecember) at different layers identified according to the severity of ozone loss. The time window selected for the calculations covers the phase of a quasi-linear ozone reduction, around day 220 (mid-August) to day 273 (end of September). Decrease of the total ozone column over Belgrano during spring is highly dependent on the meteorological conditions. Largest depletions (up to 59 %) are reached in coldest years, while warm winters exhibit significantly lower ozone loss (20 %). It has been found that about 11 % of the total O 3 loss, in the layer where maximum depletion occurs, takes place before sunlight has arrived, as a result of transport to Belgrano of air from a somewhat lower latitude, near the edge of the polar vortex, providing evidence of mixing inside the vortex. Spatial homogeneity of the vortex has been examined by comparing Belgrano results with those previously obtained for South Pole station (SPS) for the same altitude range and for 9 yr of overlapping data. Results show more than 25 % higher ozone loss rate at SPS than at Belgrano. The behaviour can be explained taking into account (i) the transport to both stations of air from a somewhat lower latitude, near the edge of the polar vortex, where sunlight reappears sooner, resulting in earlier depletion of ozone, and (ii) the accumulated hours of sunlight, which become much greater at the South Pole after the spring equinox. According to the variability of the ozone hole recovery, a clear connection between the timing of the breakup of the vortex and the monthly ozone content was found. Minimum ozone concentration of 57 DU in the 12-24 km layer remained in November, when the vortex is more persistent, while in years when the final stratospheric warming took place "very early", mean integrated ozone rose by up to 160-180 DU.

Reactive bromine in the low troposphere of Antarctica: estimations at two research sites

“…The spectral analysis of the DOAS observations shown in this work was performed with INTA's software LANA (e.g., Gil et al, 2008;Peters et al, 2017). The retrieval of BrO was centered in the 335-358 nm spectral range, including the absorption cross sections of BrO (Fleischmann et al, 2004), O 4 (Thalman and Volkamer, 2013), CH 2 O (Meller and Moortgat, 2000), OClO (Kromminga et al, 2003), NO 2 (Vandaele et al, 1998), O 3 (Bogumil et al, 2003) and of a pseudo-Ring spectra (Chance and Spurr, 1997), along with a fifth-degree closure term and constant intensity offset.…”

“…For the measurements performed from the Marambio station, the pressure (P ), temperature (T ), O 3 and NO 2 vertical profiles were obtained from the standard atmosphere for subarctic latitudes (Anderson et al, 1986). For the observations made from Belgrano, the considered P , T and O 3 profiles were obtained from monthly averaged available ozonesonde records (from 1999 to 2006, e.g., Parrondo et al, 2014), while the NO 2 profile was taken from the same standard atmosphere. The modeled atmosphere was stratified into layers of 100 m from 0 to 4 km altitude, layers of 1 km from 4 to 6 km (wider grid related to less sensibility at those altitudes) and layers of the same width of those of the standard atmosphere above this altitude.…”

“…between 100 m and 2 km, depending on the boundary layer parameterization, station and time of year (e.g., King et al, 2006;Nygård et al, 2013). Nygård et al (2013) marked the height of the boundary layer at Marambio between 1 and 1.4 km for the non-winter periods of our interest, and the ozonesondes performed at Belgrano set that height between 1 and 2.5 km at that site (e.g., Parrondo et al, 2014). However, the altitude threshold between the boundary layer and the free troposphere cannot be assessed at the time resolution of our observations.…”

The relevance of reactions of the methyl peroxy radical (CH₃O₂) and methylhypochlorite (CH₃OCl) for Antarctic chlorine activation and ozone loss

“…Severe chemical ozone loss in Antarctic spring (e.g. Solomon, 1999;Tilmes et al, 2006;Tripathi et al, 2007;Parrondo et al, 2014) leads to extremely low ozone column values, which are referred to as the ozone hole. This phenomenon has been clearly observed each Antarctic spring since the early 1980s until today (e.g.…”

Reactive bromine in the low troposphere of Antarctica. Estimations at two research sites

“…For the measurements performed 15 from Marambio station, the pressure (P), temperature (T), O3 and NO2 vertical profiles were obtained from standard atmosphere for sub-arctic latitudes (Anderson, 1986). For the observations made from Belgrano, the considered P, T and O3 profiles were obtained from monthly averaged available ozone-sonde records (from 1999 to 2006, e.g., Parrondo et al, 2014), while the NO2 profile was taken from the same standard atmosphere. The modelled atmosphere was stratified into layers of 100 m from 0 to 4 km altitude, layers of 1 km from 4 to 6 km (wider grid related to less sensibility at those altitudes) and layers 20 of the same width of those of the standard atmosphere above this altitude.…”