Mixing events revealed by anomalous tracer relationships in the Arctic vortex during winter 1999/2000

Abstract

[1] During the 1999/2000 Arctic winter SAGE III-Ozone Loss and Validation Experiment (SOLVE) campaign, high-resolution, in situ tracer data measured aboard the NASA ER-2 high-altitude aircraft revealed anomalous mixing events within the polar vortex. From January to March 2000 in the 350-500 K potential temperature range, we found mixing events during 15% of the flight time on average with significant maxima at potential temperatures of 450, 410, and 380 K. The events were spread throughout the vortex but showed a distinct minimum at 73°N and a peak at 85°N equivalent latitude. About 60% of the observed mixing events were less than 13 km wide. Based on a case study of tracer-tracer relationships, an objective simple method is introduced to detect such events using the linear nitrous oxide (N 2 O):potential temperature relationship observed deep in the vortex. Rigorous analysis and supporting evidence from total water data corroborated the validity of the method. These results suggest mixing across the polar vortex edge occurred preferentially in layers at select altitudes in the Arctic winter 1999/ 2000.

Impact of mixing and chemical change on ozone-tracer relations in the polar vortex

“…4). Indeed, Jost et al (2002) report a case where mixing across the vortex edge occurred at ≈380 K in early March of Arctic winter 2000 that did not noticeably change the O 3 /N 2 O relation. Esler and Waugh (2002) proposed to construct an artificial reference tracer from a linear combination of several longlived tracers so that a linear relation of a chemically active tracer with the artificial reference tracer would result.…”

“…Based on high altitude aircraft measurements in the Arctic in early 2000, Rex et al (2002) and Jost et al (2002) demonstrated that mixing across the vortex edge leads to an increase in the mixing ratio of ozone for a given value of N 2 O. Further, Rex et al (2002) and emphasise that although in this winter mixing lines were observed, entrainment of extra-vortex air did not significantly alter the composition of the vortex air between January and March 2000.…”

“…The ozone-tracer relation shows greater ozone mixing ratios outside the vortex than inside (e.g., Proffitt et al, 1993;Müller et al, 2001;Rex et al, 2002;Jost et al, 2002;Tilmes et al, 2004). Mixing lines connecting inside-and outside-vortex air masses are thus expected to lie between January February the inside and the outside vortex ozone-tracer relation (Fig.…”

“…Indeed, the impact of mixing on tracer-tracer relationships was neglected in early studies using the TRAC methodology (e.g., Müller et al, 1996Müller et al, , 1997. However, over the course of winter and spring, the vortex air mass will be influenced to a certain exoutside vortex air is characterised by different ozone-tracer relationships, with the outside vortex relationships showing greater ozone mixing ratios (and a stronger variability) for equal values of the tracer than inside relationships (e.g., Proffitt et al, 1990;Müller et al, 1999Müller et al, , 2002Jost et al, 2002;Tilmes et al, 2003b). Therefore, if mixing occurs between air masses inside and outside of the vortex, it will lead to points lying along the dotted mixing lines and thus above the original ozone-tracer relation in the vortex (Fig.1, top panel).…”

Variability of the Lagrangian turbulent diffusion in the lower stratosphere

“…There are also indications that we are able to reconstruct the small maximum denoted as E in Fig. 8, just before the dip, which has been identified as an intrusion of mid-latitude air by Jost et al (2002) and Konopka et al (2004). Table 1 summarizes the estimates of D based on roughness for N 2 O and O 3 , and checked by visual inspection, for all the flights of the SOLVE campaign from Kiruna.…”