The Asian summer monsoon (ASM) is known to foster transport of polluted tropospheric air into the stratosphere. To test and amend our picture of ASM vertical transport, we analyse distributions of airborne trace gas observations up to 20 km altitude near the main ASM vertical conduit south of the Himalayas. We also show that a new high-resolution version of the global chemistry climate model WACCM is able to reproduce the observations well.

A deep upper-air sounding stimulated the current investigation of internal gravity waves excited during a minor sudden stratospheric warming (SSW) in the Arctic winter 2015/16. The analysis of the radiosonde profile revealed large kinetic and potential energies in the upper stratosphere without any simultaneous enhancement of upper tropospheric and lower stratospheric values. In combination with high-resolution meteorological analyses we identified an elevated source of gravity wave excitation.

We present tracer measurements of CO and N₂O measured during the POLSTRACC aircraft campaign in winter 2015–2016. We found enhanced CO values relative to N₂O in the polar lower stratosphere in addition to the ageing of this region during winter. By using model simulations it was possible to link this enhancement to an increased mixing of the tropical tropopause. We thus conclude that the polar lower stratosphere in late winter is strongly influenced by quasi-isentropic mixing from the tropics.

This is the first research that shows concrete evidence of gravitational separation in the tropical stratosphere. This implies that gravitational separation occurs within the entire stratosphere, which gives us new insight into atmospheric dynamics.

We present an intercomparison of temperatures and horizontal winds of five meteorological data sets (ECMWF operational analysis, ERA-Interim, MERRA, MERRA-2, and NCEP/NCAR) in the Antarctic lower stratosphere. The assessment is based on 19 superpressure balloon flights during the Concordiasi field campaign in September 2010 to January 2011. The balloon data are used to successfully validate trajectory calculations with the new Lagrangian particle dispersion model MPTRAC.

Wave breaking is studied with a combination of high-resolution turbulence observations with the balloon-borne instrument LITOS and mesoscale simulations with the WRF model. A relation between observed turbulent energy dissipation rates and the occurrence of wave patterns in modelled vertical winds is found, which is interpreted as the effect of wave saturation. The change of stability plays less of a role for mean dissipation for the flights examined.

Information from long-duration balloons flying in the Southern Hemisphere stratosphere during 2014 as part of X Project Loon are used to assess the quality of a number of different reanalyses. This work assesses the potential of the X Project Loon observations to validate outputs from the reanalysis models. In particular, we examined how the model winds compared with those derived from the balloon GPS information. We also examined simulated trajectories compared with the true trajectories.

An exceptional strengthening of the middle atmospheric subtropical jet occurred without an apparent relationship with the tropospheric circulation. The analysis of this event demonstrated downward penetration of stratospheric influence to the troposphere: in the north polar region amplification of planetary wave occurred due to a deflection by the strong middle atmospheric subtropical jet, whereas in the tropics, increased tropopause temperature suppressed equatorial convective activity.

Coupled balloon-borne observations of Light Optical Aerosol Counter (LOAC), M10 meteorological GPS sondes, ozonesondes, and GPS radio occultation data are examined to identify gravity-wave (GW)-induced fluctuations on tracer gases and on the vertical distribution of stratospheric aerosol concentrations during the 2013 ChArMEx campaign. Observed mesoscale GWs induce a strong modulation of the amplitude of tracer gases and the stratospheric aerosol background.

Based on spectral and wavelet analyses, along with a diagnosis of the polarization relations, this study analyzes in situ airborne measurements from the 2008 Stratosphere-Troposphere Analyses of Regional Transport (START08) experiment to characterize gravity waves in the extratropical upper troposphere and lower stratosphere (ExUTLS) region. The focus is on the second research flight (RF02), which was dedicated to probing gravity waves associated with strong upper-tropospheric jet-front systems.

Stratospheric turbulence is essential for the atmospheric energy budget. We compare in situ observations with our LITOS method based on spectral analysis of mm-scale wind fluctuations with the Thorpe method applied to standard radiosondes. Energy dissipations rates from both methods differ by up to 3 orders of magnitude. Nevertheless, mean values are in good agreement. We present case studies on both methods and examine the applicability of the Thorpe method for calculation of dissipation rates.

The main goal of this paper is to show the geographical distribution of meridional wind for several reanalyses and to analyse the wind trends in different areas. We show two areas (100°E-160°E and 140°W-80°W) where the meridional wind is as strong as zonal wind (which is normally dominant in the stratosphere). The trends of meridional wind are significant mostly at 99% level in these areas and insignificant outside. The problem with zonal averages could affect the results.