Mixing and ageing in the polar lower stratosphere in winter 2015–2016

Krause, Jens; Hoor, Peter; Engel, Andreas; Plöger, Felix; Grooß, Jens‐Uwe; Bönisch, Harald; Keber, Timo; Sinnhuber, Björn-Martin; Woiwode, Wolfgang; Oelhaf, H.

doi:10.5194/acp-18-6057-2018

Cited by 25 publications

(31 citation statements)

References 82 publications

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“…To investigate how the observed HNO 3 distribution is affected by nitrification, three research flights have been selected. The first flight was carried out on 20 January 2016 during the coldest phase of the winter (Manney and Lawrence, 2016), with PSCs ranging down to flight level. The second flight took place on 31 January 2016 after a strong PSC phase.…”

Section: Gloria Observations and Clams Simulations Of Selected Flightmentioning

confidence: 99%

“…Here, we present observations of nitrification of the LMS in the unusually cold Arctic winter 2015-2016 by the airborne limb-imaging Fourier transform infrared (FTIR) spectrometer GLORIA (Gimballed Limb Observer for Radiance Imaging of the Atmosphere, Friedl-Vallon et al, 2014;Riese et al, 2014). In that winter, an extraordinarily cold and stable polar vortex (Matthias et al, 2016;Manney and Lawrence, 2016) promoted a long-lasting PSC phase from mid-December until the end of February with a large vertical extent (Pitts et al, 2018;Voigt et al, 2018) reaching down into the LMS.…”

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confidence: 99%

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Nitrification of the lowermost stratosphere during the exceptionally cold Arctic winter 2015–2016

Braun

Grooß²,

Woiwode

et al. 2019

Atmos. Chem. Phys.

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Abstract. The Arctic winter 2015–2016 was characterized by exceptionally low stratospheric temperatures, favouring the formation of polar stratospheric clouds (PSCs) from mid-December until the end of February down to low stratospheric altitudes. Observations by GLORIA (Gimballed Limb Observer for Radiance Imaging of the Atmosphere) on HALO (High Altitude and LOng range research aircraft) during the PGS (POLSTRACC–GW-LCYCLE II–SALSA) campaign from December 2015 to March 2016 allow the investigation of the influence of denitrification on the lowermost stratosphere (LMS) with a high spatial resolution. Two-dimensional vertical cross sections of nitric acid (HNO3) along the flight track and tracer–tracer correlations derived from the GLORIA observations document detailed pictures of wide-spread nitrification of the Arctic LMS during the course of an entire winter. GLORIA observations show large-scale structures and local fine structures with enhanced absolute HNO3 volume mixing ratios reaching up to 11 ppbv at altitudes of 13 km in January and nitrified filaments persisting until the middle of March. Narrow coherent structures tilted with altitude of enhanced HNO3, observed in mid-January, are interpreted as regions recently nitrified by sublimating HNO3-containing particles. Overall, extensive nitrification of the LMS between 5.0 and 7.0 ppbv at potential temperature levels between 350 and 380 K is estimated. The GLORIA observations are compared with CLaMS (Chemical Lagrangian Model of the Stratosphere) simulations. The fundamental structures observed by GLORIA are well reproduced, but differences in the fine structures are diagnosed. Further, CLaMS predominantly underestimates the spatial extent of HNO3 maxima derived from the GLORIA observations as well as the overall nitrification of the LMS. Sensitivity simulations with CLaMS including (i) enhanced sedimentation rates in case of ice supersaturation (to resemble ice nucleation on nitric acid trihydrate (NAT)), (ii) a global temperature offset, (iii) modified growth rates (to resemble aspherical particles with larger surfaces) and (iv) temperature fluctuations (to resemble the impact of small-scale mountain waves) slightly improved the agreement with the GLORIA observations of individual flights. However, no parameter could be isolated which resulted in a general improvement for all flights. Still, the sensitivity simulations suggest that details of particle microphysics play a significant role for simulated LMS nitrification in January, while air subsidence, transport and mixing become increasingly important for the simulated HNO3 distributions towards the end of the winter.

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Section: Gloria Observations and Clams Simulations Of Selected Flightmentioning

confidence: 99%

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confidence: 99%

Nitrification of the lowermost stratosphere during the exceptionally cold Arctic winter 2015–2016

Braun

Grooß²,

Woiwode

et al. 2019

Atmos. Chem. Phys.

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“…Such conditions in the ridge of extratropical baroclinic waves resemble the predictions of the idealized simulations from Kunkel et al (2016). Thus, the flight was planned in the ridge of a synoptic-scale baroclinic wave 35…”

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confidence: 54%

Evidence of small-scale quasi-isentropic mixing in ridges of extra-tropical baroclinic waves

Kunkel¹,

Hoor²,

Kaluza³

et al. 2019

Preprint

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<p><strong>Abstract.</strong> Stratosphere&#8211;troposphere exchange within extratropical cyclones provides the potential for anthropogenic and natural surface emissions to rapidly reach the stratosphere as well as for ozone from the stratosphere to penetrate deep into the troposphere, even down into the boundary layer. The efficiency of this process directly influences the surface climate, the chemistry in the stratosphere, the chemical composition of the extratropical transition layer, and surface pollution levels. Here, we present evidence for a mixing process within extratropical cyclones which has gained only little attention so far and which fosters the transport of tropospheric air masses into the stratosphere in ridges of baroclinic waves. We analyzed airborne measurement data from a research flight of the WISE (Wave driven isentropic exchange) campaign over the North Atlantic in autumn 2017 supported by forecasts from a numerical weather prediction model and trajectory calculations. Further detailed process understanding is obtained from experiments of idealized baroclinic life cycles. The major outcome of this analysis is that air masses mix in the region of the tropopause and potentially enter the stratosphere in ridges of baroclinic waves at the anti-cyclonic side of jet without changing their potential temperature drastically. This quasi-isentropic exchange occurs above the outflow of warm conveyor belts, in regions which exhibit enhanced static stability in the lower stratosphere and a Kelvin&#8211;Helmholtz instability across the tropopause. The enhanced static stability is related to radiative cooling below the tropopause and the presence of small scale waves. The Kelvin&#8211;Helmholtz instability is related to vertical shear of the horizontal wind associated to small scale waves at the upper edge of the jet-stream. The instability leads to the occurrence of turbulence and consequent mixing of trace gases in the tropopause region. While the overall relevance of this process has yet to be assessed, it has the potential to significantly modify the chemical composition of the extratropical transition layer in the lowermost stratosphere in regions which have previously gained only little attention in terms of mixing in baroclinic waves.</p>

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“…This section provides an overview of the measurement principles of the in situ instruments used in the present work. In addition to the dedicated trace gas measurements, the Basis HALO Measurement and Sensor System (BAHAMAS) provides meteorological parameters along the flight trajectory (Krautstrunk and Giez, 2012;Giez et al, 2017).…”

Section: Airborne In Situ Measurementsmentioning

confidence: 99%

Chlorine partitioning in the lowermost Arctic vortex during the cold winter 2015/2016

Marsing

Jurkat‐Witschas

Grooß³

et al. 2019

Atmos. Chem. Phys.

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Activated chlorine compounds in the polar winter stratosphere drive catalytic cycles that deplete ozone and methane, whose abundances are highly relevant to the evolution of global climate. The present work introduces a novel dataset of in situ measurements of relevant chlorine species in the lowermost Arctic stratosphere from the aircraft mission POLSTRACC-GW-LCYCLE-SALSA during winter 2015/2016. The major stages of chemical evolution of the lower polar vortex are presented in a consistent series of high-resolution mass spectrometric observations of HCl and ClONO 2 . Simultaneous measurements of CFC-12 are used to derive total inorganic chlorine (Cl y ) and active chlorine (ClO x ). The new data highlight an altitude dependence of the pathway for chlorine deactivation in the lowermost vortex with HCl dominating below the 380 K isentropic surface and ClONO 2 prevailing above. Further, we show that the Chemical Lagrangian Model of the Stratosphere (CLaMS) is generally able to reproduce the chemical evolution of the lower polar vortex chlorine budget, except for a bias in HCl concentrations. The model is used to relate local measurements to the vortex-wide evolution. The results are aimed at fostering our understanding of the climate impact of chlorine chemistry, providing new observational data to complement satellite data and assess model performance in the climatesensitive upper troposphere and lower stratosphere region.

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Mixing and ageing in the polar lower stratosphere in winter 2015–2016

Cited by 25 publications

References 82 publications

Nitrification of the lowermost stratosphere during the exceptionally cold Arctic winter 2015–2016

Nitrification of the lowermost stratosphere during the exceptionally cold Arctic winter 2015–2016

Evidence of small-scale quasi-isentropic mixing in ridges of extra-tropical baroclinic waves

Chlorine partitioning in the lowermost Arctic vortex during the cold winter 2015/2016

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