On the observation of mesospheric air inside the arctic stratospheric polar vortex in early 2003

Abstract

Abstract. During several balloon flights inside the Arctic polar vortex in early 2003, unusual trace gas distributions were observed, which indicate a strong influence of mesospheric air in the stratosphere. The tuneable diode laser (TDL) instrument SPIRALE (Spectroscopie InFrarouge par Absorption de Lasers Embarqués) measured unusually high CO values (up to 600 ppb) on 27 January at about 30 km altitude. The cryosampler BONBON sampled air masses with very high molecular Hydrogen, extremely low SF6 and enhanced CO values on 6 March at about 25 km altitude. Finally, the MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) Fourier Transform Infra-Red (FTIR) spectrometer showed NOy values which are significantly higher than NOy* (the NOy derived from a correlation between N2O and NOy under undisturbed conditions), on 21 and 22 March in a layer centred at 22 km altitude. Thus, the mesospheric air seems to have been present in a layer descending from about 30 km in late January to 25 km altitude in early March and about 22 km altitude on 20 March. We present corroborating evidence from a model study using the KASIMA (KArlsruhe Simulation model of the Middle Atmosphere) model that also shows a layer of mesospheric air, which descended into the stratosphere in November and early December 2002, before the minor warming which occurred in late December 2002 lead to a descent of upper stratospheric air, cutting of a layer in which mesospheric air is present. This layer then descended inside the vortex over the course of the winter. The same feature is found in trajectory calculations, based on a large number of trajectories started in the vicinity of the observations on 6 March. Based on the difference between the mean age derived from SF6 (which has an irreversible mesospheric loss) and from CO2 (whose mesospheric loss is much smaller and reversible) we estimate that the fraction of mesospheric air in the layer observed on 6 March, must have been somewhere between 35% and 100%.

On the vertical structure of the stratosphere at midlatitudes during the first stage of the polar vortex formation and in the polar region in the presence of a large mesospheric descent

“…SPIRALE measurements therefore extend the correlation values to lower N 2 O values thanks to the large mesospheric descent observed by the SPIRALE measurements. This mesospheric descent has also been observed on March 2003 by other instruments [ Engel et al , 2005].…”

“…Above 23 km, the measurements show a very intense mesospheric descent compared to those referred to by Plumb et al [2002] because the mixing ratio of CO observed is as large as 600 ppbv. This large mesospheric descent has also been observed later, in March 2003 [ Engel et al , 2005]. Measurements allow us to determine new CH 4 :N 2 O correlation values.…”

Impact of mesospheric intrusions on ozone‐tracer relations in the stratospheric polar vortex

“…Here we analyze ozone‐tracer relations in the Arctic winter 2002/2003, when an intrusion of mesospheric air into the stratosphere was observed [ Engel et al , 2006; Huret et al , 2006]. (Note that the term “intrusion” is used here in a different sense than quasi‐isentropic filamentary intrusions into the vortex from the extratropics, a concept that frequently also appears in the literature.)…”

“…The mesospheric intrusion may be identified as strongly enhanced CO mixing ratios. It occurred in the Arctic vortex in early 2003 in a layer descending from ∼30 km in late January to ∼25 km by early March [ Engel et al , 2006; Huret et al , 2006]. This mesospheric air was sampled again in the vortex in late March [ Engel et al , 2006; Wetzel et al , 2006].…”

High‐latitude remote sensing of mesospheric wind speeds and carbon monoxide

“… de Zafra and Muscari [2004] measured CO column densities that regularly reached above 10 17 cm −2 , in good agreement with Solomon et al 's [1985] predictions. Recently, interest in upper‐atmospheric CO has increased, with both satellites and ground‐based instruments used to monitor concentrations [e.g., Dupuy et al , 2004; Filipiak et al , 2005; Engel et al , 2005; Jin et al , 2005; Velazco et al , 2007].…”