Institut für Atmosphäre und Umwelt

Andreas Engel

Institut für Atmosphäre und Umwelt

J.W. Gotehe Universität Frankfurt

• Mean age as a diagnostic of stratospheric transport• Determination of mean age• Mean age trends – model and measurement• TTL and stratospheric Halogen budget, incl. Br from

VSLS• Possible contributions

Variability and long term change in atmospheric transport time scales and the halogen budget

Institut für Atmosphäre und Umwelt

Institut für Atmosphäre und Umwelt

Stratosphärische (Ballon) und troposphärische SF6 Messungen:Bestimmung des mittleren

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Institut für Atmosphäre und Umwelt

Vertical profiles of CO2 derived mean age for mid latitudes. For the trend analysis only data above the 30 hPa level (shown by the red line) are used. Data obtained since 1995 which have a higher precision are shown as large bold symbols.

Vertical profiles of CO2 derived mean age for high latitudes. For the trend analysis only data above the 80 hPa level (shown by the blue line) are used. Data obtained since1995 which have a higher precision are shown as large bold symbols.

Vertical profiles of mean age derived from CO2 observations

Institut für Atmosphäre und Umwelt

Temporal evolution of mean age derived from CO2 observations. The data have been filtered based on the pressure criterium (above 30 hPa for mid latitudes, above 80 hPa for high latitudes). The systematic error is included at 1.0 years prior to 1990 and 0.3 years since 1990. Linear regression yields a slope of - 0.016 (+/- 0.018) years of mean age per year. The small symbols show the individual observations, color coded based on their distance relative to the selection criterium.

Temporal evolution of mean age above 30/80 hpa at mid and high latitudes from balloon-borne observations

Institut für Atmosphäre und Umwelt

Model calculation of mean age

Austin et al., JGR, in press, 2006

Institut für Atmosphäre und Umwelt

VSLS species in the tropopause region

• New GC/MS system set up in late 2005

• Measurable VSLS include: CHBr3, CH2Br2, CH2Br2, CH3I, CH2Cl2, CHCl3, C2H5Cl, CH2ClCH2Cl, C2Cl4, C2HCl3.

• Measurements of VSLS species in TTL and lower tropical stratosphere performed in 2005 (2 balloon flights)

• Mid latitude Flight in October 2006 with measurements of VSLS; new sampler shows good sample stability.

• Next flight planned in October 2007 in Teresina 5°S, Brazil).

• In-situ GC/MS measurements planned for HALO missions in 2009/2010.

Institut für Atmosphäre und Umwelt

Tropical bromine budget – June 2005, prel.

organic tropical bromine budget on 8.6.2005

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total bromine

total Br from Halons

total Br from CH3Br

total Br from VSLS

total Bry

Bry from Halons

Bry from CH3Br

Bry from VSLS

Some things we do and do not understand

Total Br measured in the TTL is about 17 ppt, incl. Contributions from 4 Halons, CH3Br, CH2Br2, CH2BrCl, CHCl2Br.

There was no Bromoform up there, but even traces (about 0.1 ppt) of CH3I (which is shorter lived)

Bry derived from BrO measurements is about 21 ppt

What brings the extra Br up there (if not Bromoform)??

Institut für Atmosphäre und Umwelt

Possible contributions to G-Sparc

• Age is the best possible diagnostic of the strength of the Brewer-Dobson circulation. Changes in the Brewer Dobson circulation are of prime interest, as they are a direct effect of climate change.

• Regular mean age observations in the stratosphere up to 30 km are needed in order to assess if such a change is occuring. Organic Halogen budget can be measured simultaneously.

• Satellite observations (MIPAS-ENV) have improved very much lately. Regular geophysical validation is needed in order to ensure the data quality. Averaging is needed in order to derive mean age.

• Balloon-borne spot observations are still the only reliable way of getting mean age and Halogen budget information above 20 km.

• Continuation proposal for CAWSES submitted; should allow funding of mean age activities until mid 2009 (if granted).

• Activity would fit very well in SPARC, co-operation with modellers needed.

Institut für Atmosphäre und Umwelt

Possible contributions to G-Sparc• One profile observation per year should – due to the high precision - be

sufficient to get a picture of long term mean age and halogen evolution. Global variability, seasonal effects etc. are better covered by satellite data (allthough it is not clear yet, if MIPAS can measure SF6 in the reduced resolution mode). CO2 with the neccesary precision and accuracy is not possible from space yet.

• Mini-sampler with 26 sample bottles has been develloped and tested at our institute. Total payload weight 100 kg. Can be flown with rather small balloons, which can be launched quite easily. Measurements of age tracers and complete halogen budgets possible, incl. VSLS.

• Develop chemical ionisation GC/MS method for selective bromine screening method, to get better detection limits (below 0.1 ppt, compared to about 0.2-0.5 ppt now) and to allow measurements of mixed bromo-chlorocarbons.

Institut für Atmosphäre und Umwelt

Proposal and discussion• Proposal:

– maintain data base of stratospheric age tracer measurements (incl. Satellite data and other observations); maintain tropospheric reference time series; update time series with a flight on a yearly basis; provide time series to global modellers.

– Maintain and improve data base on halogen budget, including VSLS species, improve analytical system.

• Suggestion for Discussion:

– Prepare a HALO mission with emphasis on transport into and in the TTL and the chemical budget of the TTL??? Such a mission could be done in 2010 or 2011. Funding of flight hours from DFG HALO budget possible. Co-ordination with one or 2 balloon flights for information on altitude above 15 km and MIPAS/Sciamachy satellite observations?

Institut für Atmosphäre und Umwelt

Required measurements for TTL mission

• Age tracers CO2, SF6, CF4, C2F6 …• Water vapour• Ozone• Long lived tracers (N2O, CH4) ..• Short lived tracers (Acetone, VSLS etc.)• Inorganic Br and Cl species, incl. what could be on

aerosols (PGI!)• Aersols, incl. their chemical composition (PGI)• NOx, NOy, HCl

• Red: could be measured from balloon also