Small-scale transport structures in the Arctic winter 2009/2010

The CRISTA-NF (Cryogenic Infrared Spectrometers and Telescope for the Atmosphere – New Frontiers) instrument is an airborne infrared limb sounder operated aboard the Russian research aircraft M55-Geophysica. The instrument successfully participated in a large Arctic aircraft campaign within the RECONCILE (Reconciliation of essential process parameters for an enhanced predictability of Arctic stratospheric ozone loss and its climate interactions) project from January to March 2010 in Kiruna, Sweden. This paper concentrates on the measurements during one flight of the campaign, which took place on 2 March in the vicinity of the polar vortex. We present two-dimensional cross-sections of volume mixing ratios for the trace gases CFC-11, O3, and ClONO2 with an unprecedented vertical resolution of about 500 to 600 m for a large part of the observed altitude range and a dense horizontal sampling along flight direction of ≈ 15 km. The trace gas distributions show several structures like the polar vortex and filaments composed of air masses of different origin. The situation during the analysed flight is simulated by the chemistry and transport model CLaMS (Chemical Lagrangian Model of the Stratosphere) and compared with the measurements to assess the performance of the model with respect to advection, mixing, and the chemistry in the polar vortex. These comparisons confirm the capability of CLaMS to reproduce even very small-scale structures in the atmosphere. Based on the good agreement between simulation and observation, we use a model concept utilising artificial tracers to further analyse the CRISTA-NF observations in terms of air mass origin. A characteristic of the Arctic winter 2009/10 was a sudden stratospheric warming in early December that led to a split of the polar vortex. The vortex re-established at the end of December. Our passive tracer simulations suggest that large parts of the re-established vortex consisted to about 45% of high- and mid-latitude air.