Interaction between dynamics and chemistry of ozone in the setup phase of the Northern Hemisphere polar vortex

Abstract

[1] The morphology and evolution of the stratospheric ozone (O 3 ) distribution at high latitudes in the Northern Hemisphere (NH) are examined for the late summer and fall seasons of 1999. This time period sets the O 3 initial condition for the SOLVE/THESEO field mission performed during winter 1999/2000. In situ and satellite data are used along with a three-dimensional model of chemistry and transport (CTM) to determine the key processes that control the distribution of O 3 in the lower-to-middle stratosphere. O 3 in the vortex at the beginning of the winter season in late November is found to be nearly constant from 500 to above 800 K with a value at 3 ppmv ± $10%. Values outside the vortex above 550 K are up to a factor of 2 higher and increase significantly with potential temperature. The seasonal time series of data from POAM shows that the relatively low O 3 mixing ratios, which characterize the vortex in late November, are already present at high latitudes at the end of summer in mid-September before the vortex circulation sets up. Analysis of the CTM output shows that the minimum O 3 and increase in variance in the middle stratosphere in late summer are the result of (1) stirring of polar concentric O 3 gradients by nascent wave-driven transport and (2) an acceleration of net photochemical loss with decreasing solar illumination. The segregation of low O 3 mixing ratios into the vortex as the circulation strengthens through the fall suggests a possible feedback role between O 3 chemistry and the vortex formation dynamics that may need to be better understood in order to make confident predictions of the recovery of NH O 3 at high latitudes.

The contributions of chemistry and transport to low arctic ozone in March 2011 derived from Aura MLS observations

“…In the absence of a large wave event such as a major warming, vortex temperatures in fall and early winter are similar each year, producing diabatic descent and radiatively driven downward transport of the O 3 column [Kawa et al, 2002]. In addition, Kawa et al [2002] report that vortex O 3 profiles in November have low IA variability; thus, the combination of low IA variability in both vortex O 3 profiles and descent rates leads to low IA variability in vortex column O 3 . In late January, wave driving often increases and so do the ranges of vortex temperature, mean column O 3 , and area (Figures 3,2a,and 2c).…”

“…Thus, the IA variability of vortex O 3 in fall is low because there is little IA variability in the radiative and photochemical processes controlling it [Kawa et al, 2002]. Vortex temperatures reflect the low IA variability in early season wave transport.…”

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

“…8): In the incipient vortex the vortex air mass is characterised by low ozone mixing ratios; the result of polar ozone destruction due to NO x driven chemical cycles in summer (e.g., Farman, 1985) and autumn (Kawa et al, 2002;Tilmes et al, 2005a). Although the vortex air mass is separated to a certain extent from ozone-rich, mid-latitude air, the vortex is not yet completely isolated.…”

Ozone loss derived from balloon-borne tracer measurements in the 1999/2000 Arctic winter

“…The only odd feature was a notch of lower ozone around 30 hPa observed during the OMS in situ balloon flight on 19 November, which was attributed as being a dynamical feature which developed during the vortex formation (Salawitch et al, 2002). However, analysis of the available satellite data indicates that ozone variability inside the vortex was low and that this feature was anomalous (Kawa et al, 2002). Accordingly, early winter ozone/tracer relations have been calculated from balloon profiles, whose estimated uncertainties reflect the variability in the O 3 /tracer Ray et al, 2002;Richard et al, 2001).…”

“…In late 1999 the Arctic vortex was isolated and well-mixed (Kawa et al, 2002). The only odd feature was a notch of lower ozone around 30 hPa observed during the OMS in situ balloon flight on 19 November, which was attributed as being a dynamical feature which developed during the vortex formation (Salawitch et al, 2002).…”