Analysis of a rapid increase of stratospheric ozone during late austral summer 2008 over Kerguelen (49.4° S, 70.3° E)
Author:
Bencherif H.,El Amraoui L.,Kirgis G.,Leclair De Bellevue J.,Hauchecorne A.,Mzé N.,Portafaix T.
Abstract
Abstract. This paper reports on an increase of ozone event observed over Kerguelen (49.4° S, 70.3° E) in relationship with large-scale isentropic transport. It is evidenced from ground-based observations, together with satellite global observations and assimilated fields. The study is based on the analyses of the first ozonesonde experiment never recorded at the Kerguelen site in the framework of a French campaign called ROCK that took place from April to August 2008. Comparisons and interpretations of the observed event are supported by co-localised SAOZ observations, by global mapping of tracers (O3, N2O and columns of O3) from Aura/MLS and Aura/OMI experiments, and by model simulations of Ertel Potential Vorticity initialised by ECMWF (European Centre for Medium-Range Weather Forecasts) data reanalyses. Satellite and ground-based observational data revealed a consistent increase of ozone in the local stratosphere by mid-April 2008. Additionally, Ozone (O3) and nitrous oxide (N2O) profiles obtained during January–May 2008 by the Microwave Lamb Sounder (MLS) aboard the Aura satellite are assimilated into MOCAGE (MOdèle de Chimie Atmosphérique à Grande Echelle), a global three-dimensional chemistry transport model of Météo-France. The assimilated total O3 values are consistent with SAOZ ground observations (within ±5%), and isentropic distributions of O3 are matching well with maps of advected potential vorticity (APV) derived from the MIMOSA model, a high-resolution advection transport model, and from ECMWF reanalysis. The studied event seems to be related to isentropic transport of air masses that took place simultaneously in the lower- and middle-stratosphere, respectively from the polar region and from tropics to the mid-latitudes. In fact, the studied ozone increase by mid April 2008 results simultaneously: (1) from an equator-ward departure of polar air masses characterised with a high-ozone layer in the lower stratosphere (nearby the 475 K isentropic level), and (2) from a reverse isentropic transport from tropics to mid- and high-latitudes in the upper stratosphere (nearby the 700 K level). The increase of ozone observed over Kerguelen from the 16-April ozonesonde profile is then attributed to a concomitant isentropic transport of ozone in two stratospheric layers: the tropical air moving southward and reaches over Kerguelen in the upper stratosphere, and the polar air passing over the same area but in the lower stratosphere.
Publisher
Copernicus GmbH
Reference34 articles.
1. Bencherif, H., Portafaix, T., Baray, J.-L., Morel, B., Baldy, S., Leveau, J., Hauchecorne, A., Keckhut, P., Moorgawa, A., Michaelis, M. M., and Diab, R.: LIDAR observations of lower stratospheric aerosols over South Africa linked to large scale transport across the southern subtropical barrier, J. Atmos. Solar- Terrestrial Phys., 65(6), 707–715, 2003. 2. Bencherif, H., El Amraoui, L., Semane, N., Massart, S., Vidyaranya D. C., Hauchecorne, A., and Peuch, V.-H.: Examination of the 2002 major warming in the Southern Hemisphere using ground-based and Odin/SMR assimilated data: stratospheric ozone distributions and tropic/mid-latitude exchange, Can. J. Phys., 85, 1287–1300, 2007. 3. Bertaux, J. L., Hauchecorne, A., Mangin, A., Cot, C., Théodore, B., Talagrand, O., Fussen, D., Simon, P. C., Kyrölä, E., Roscoe, H., Hembise, O., and Brasseur, G. P.: The Msdol Project: Assimilation Of Gomos Ozone Data In A 3-D Chemistry-Transport Model, Phys. Chem. Earth, 24(5), 435–437, 1999. 4. Brinksma, E. J., Meijer, Y. J., Connor, B. J., Manney, G. L., Bergwer, J. B., Bodeker, G. E., Boyd, I. S., Liley, J. B., Hogervorst, W., Hovenier, J. W., Livesey, N. J., and Swart, D. P. J.: Analysis of Record-Low Ozone Values During the 1997 Winter over Lauder, New Zealand, Geophys. Res. Lett., 25(15), 2785–2788, 1998. 5. Courtier, P., Freydier, C., Geleyn, J.-F. Rabier, F. and Rochas, M.: The ARPEGE project at Météo-France, in: Workshop on numerical methods in atmospheric models, Vol. 2, 193–231, 1991.
|
|