Seasonal cycles and variability of O<sub>3</sub> and H<sub>2</sub>O in the UT/LMS during SPURT

Abstract

Abstract. Airborne high resolution in situ measurements of a large set of trace gases including ozone (O 3 ) and total water (H 2 O) in the upper troposphere and the lowermost stratosphere (UT/LMS) have been performed above Europe within the SPURT project. SPURT provides an extensive data coverage of the UT/LMS in each season within the time period between November 2001 and July 2003.In the LMS a distinct spring maximum and autumn minimum is observed in O 3 , whereas its annual cycle in the UT is shifted by 2-3 months later towards the end of the year. The more variable H 2 O measurements reveal a maximum during summer and a minimum during autumn/winter with no phase shift between the two atmospheric compartments.For a comprehensive insight into trace gas composition and variability in the UT/LMS several statistical methods are applied using chemical, thermal and dynamical vertical coordinates. In particular, 2-dimensional probability distribution functions serve as a tool to transform localised aircraft data to a more comprehensive view of the probed atmospheric region. It appears that both trace gases, O 3 and H 2 O, reveal the most compact arrangement and are best correlated in the view of potential vorticity (PV) and distance to the local tropopause, indicating an advanced mixing state on these surfaces. Thus, strong gradients of PV seem to act as a transport barrier both in the vertical and the horizontal direction. The alignment of trace gas isopleths reflects the existence of a year-round extra-tropical tropopause transition layer. The SPURT measurements reveal that this layer is mainly affected by stratospheric air during winter/spring and by tropospheric air during autumn/summer.Correspondence to: M. Krebsbach (m.krebsbach@fz-juelich.de) Normalised mixing entropy values for O 3 and H 2 O in the LMS appear to be maximal during spring and summer, respectively, indicating highest variability of these trace gases during the respective seasons.

Jet characterization in the upper troposphere/lower stratosphere (UTLS): applications to climatology and transport studies

“…The method of Archer and Caldeira (2008), developed for assessing longterm average trends, defines monthly-mean mass-weighted average wind speeds and pressures for the upper tropospheric jets. As noted by Davis (2007, 2008a,b), methods such as those of Koch et al (2006) and Archer and Caldeira (2008) reduce or eliminate information on the vertical structure of the upper tropospheric jets by averaging in the vertical. Schiemann et al (2009) avoided this simplification by extending the method of Koch et al (2006) to a threedimensional (3-D) framework to examine seasonal variability of jets in the Tibetan Plateau region.…”

“…As noted by Davis (2007, 2008a,b), methods such as those of Koch et al (2006) and Archer and Caldeira (2008) reduce or eliminate information on the vertical structure of the upper tropospheric jets by averaging in the vertical. Schiemann et al (2009) avoided this simplification by extending the method of Koch et al (2006) to a threedimensional (3-D) framework to examine seasonal variability of jets in the Tibetan Plateau region. Davis (2007, 2008a) retain more vertical jet structure information, characterizing the jets on the surface defined by the maximum windspeed at each horizontal location.…”

“…Several previous studies have presented schemes for automating identification of the upper tropospheric jets (e.g., Koch et al, 2006;Davis, 2007, 2008a; Archer and Caldeira, 2008;Schiemann et al, 2009). Koch et al (2006) define the jets over a vertical region from 400 to 100 hPa, and use their characterization to develop a two-dimensional (2-D) climatology of upper tropospheric jets.…”

“…Koch et al (2006) define the jets over a vertical region from 400 to 100 hPa, and use their characterization to develop a two-dimensional (2-D) climatology of upper tropospheric jets. The method of Archer and Caldeira (2008), developed for assessing longterm average trends, defines monthly-mean mass-weighted average wind speeds and pressures for the upper tropospheric jets.…”

Stratosphere–troposphere exchange (STE) in the vicinity of North Atlantic cyclones

“…For instance, the injection of stratospheric air into the troposphere can enhance the ozone concentration in the troposphere significantly (e.g., Danielsen, 1968;Stevenson et al, 2006), even down to the boundary layer (Johnson and Viezee, 1967;Lefohn et al, 2011;Lin et al, 2012). On the other side, the amount of water vapour in the extratropical lower stratosphere can strongly increase when tropospheric air is transported across the tropopause (e.g., Krebsbach et al, 2006). Even polluted air from the boundary layer can be transported into the extratropical lower stratosphere (e.g., Arnold et al, 1997;Chen et al, 2012).…”