Improved global distributions of SF6 and mean age of stratospheric air by use of new spectroscopic data

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, to be published), 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, variablilities and trends, and compare to previous versions and independent in situ observations. 

References:

Haenel, F. J., Stiller, G. P., von Clarmann, T., Funke, B., Eckert, E., Glatthor, N., Grabowski, U., Kellmann, S., Kiefer, M., Linden, A., and Reddmann, T.: 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.
Stiller, G. P., von Clarmann, T., Höpfner, M., Glatthor, N., Grabowski, U., Kellmann, S., Kleinert, A., Linden, A., Milz, M., Reddmann, T., Steck, T., Fischer, H., Funke, B., López-Puertas, M., and Engel, A.: 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., von Clarmann, T., Haenel, F., Funke, B., Glatthor, N., Grabowski, U., Kellmann, S., Kiefer, M., Linden, A., Lossow, S., and López-Puertas, M.: 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., Li, Z., Nemtchinov, V., and Cherukuri, A.: Spectral Absorption–Coefficient Data on HCFC-22 and SF6 for Remote– Sensing Applications, J. Quant. Spectrosc. Radiat. Transfer, 52, 323–332, 1994.