Transport timescales and halogen budget in the Arctic polar Vortex and the UTLS during HALO-ASCCI

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The project ASCCI is a HALO mission in the Northern Hemisphere polar late winter to early spring to study ozone in the Arctic lowermost stratosphere and upper troposphere. The scientific background of the ASCCI campaign is described in the campaign co-ordination proposal by the same applicant (Andreas Engel) and Björn-Martin Sinnhuber (KIT Karlsruhe). Here we focus specifically on aspects related to the work proposed at University Frankfurt in relation to the ASCCI campaign. University Frankfurt operates an in-situ gas chromatograph with electron capture (GC-ECD) and with mass spectrometric (GC-MS) detection. The instrument is capable of measuring a wide suite of halocarbons, using both Electron Impact (EI) and Negative Chemical Ionization (NCI), and also the mean age tracer SF6. We focus on aspects related to halocarbons, their atmospheric distribution, on total halogen loading of the atmosphere, available chlorine and bromine in the stratosphere and on aspects of mean age of air, specifically for the polar winter conditions to be investigated during ASCCI. The main research question we will adress within this proosal are: - how has the atmospheric chlorine budget chenged in comparison to the winter 2015/2016 when the last Arctic polar winter campaign with HALO was performed. - how has the atmospheric bromine budget chenged in comparison to the winter 2015/2016 when the last Arctic polar winter campaign with HALO was performed - what are typical transport times (mean age of air) in the lower stratosphere using a new and improved method to determine mean age? - How do chlroine and bromine budgets and also mean age compare to the Southern Hemisphere distributions, in particular if data are comared in a vortex-relative coordinate system?