A044-0005
Improved Global Distributions of SF6 and Mean Age of Stratospheric Air by Use of New Spectroscopic Data

Tuesday, 8 December 2020
Poster
Gabriele P Stiller1, Jeremy J. Harrison2, Florian Haenel1, Norbert Glatthor1, Sylvia Kellmann1, Thomas von Clarmann1, Sheena Loeffel3 and Rostislav Kouznetsov4, (1)Karlsruhe Institute of Technology, Karlsruhe, Germany, (2)University of Leicester, Department of Physics and Astronomy, Leicester, United Kingdom, (3)German Aerospace Center DLR Oberpfaffenhofen, Wessling, Germany, (4)Finnish Meteorological Institute, Helsinki, Finland
Abstract:
The first and only global data set of mean age of stratospheric air (AoA) with dense day and night coverage has been derived from MIPAS observations by analysis of the spectral signature of SF6 (Stiller et al., 2008, 2012; Haenel et al., 2015). Since SF6 is a tracer with no sinks in the troposphere and stratosphere and an almost linearly increasing atmospheric abundance, it is often used to derive information on stratospheric transport and mixing due to the Brewer Dobson Circulation, quantified usually as mean age of stratospheric air (AoA). The global data sets of AoA derived so far from MIPAS observations, on basis of spectroscopically measured absorption cross sections by Varanasi et al. (1994), had a high bias in the middle to upper stratosphere compared to balloon borne in situ observations from the 1990s. By applying a new spectroscopic data set measured in the laboratory recently (J.J. Harrison, 2020), we show that part of the high bias in AoA can be removed, and the residuals between measured and modelled atmospheric spectra can be decreased significantly. In this presentation we discuss the new SF6 and AoA distributions, variabilities and trends, compare to previous versions and independent in situ observations, and show comparisons to recent model runs.

References:

Haenel, F. J., et al., Reassessment of MIPAS age of air trends and variability, Atmos. Chem. Phys., 15, 13161-13176, https://doi.org/10.5194/acp-15-13161-2015, 2015.

Harrison, J. J., New infrared absorption cross sections for the infrared limb sounding of sulfur hexafluoride (SF6), Journal of Quantitative Spectroscopy & Radiative Transfer, doi: https://doi.org/10.1016/j.jqsrt.2020.107202, 2020.

Stiller, G. P., et al., Global distribution of mean age of stratospheric air from MIPAS SF6 measurements, Atmos. Chem. Phys., 8, 677-695, https://doi.org/10.5194/acp-8-677-2008, 2008.

Stiller, G. P., et al., Observed temporal evolution of global mean age of stratospheric air for the 2002 to 2010 period, Atmos. Chem. Phys., 12, 3311-3331, https://doi.org/10.5194/acp-12-3311-2012, 2012.

Varanasi, P., et al., Spectral absorption-coefficient data on HCFC-22 and SF6 for remote-sensing applications, Journal of Quantitative Spectroscopy and Radiative Transfer, 52, 323-332, 1994.

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