Recent measurements have shown that the mixing ratio of some long lived chlorine compounds have started to decline in the troposphere due to the limitations enforced by the Montreal Protocol. We propose to use a suit of balloonbome instruments which have all been tested and proven to provide reliable measurements to characterise the partitioning of chlorine and bromine compounds from the source, reservoir and reactive families during the peak of stratospheric chlorine loading which is expected to occur between 1997 and 1999.
Using a combination of remote sensing and in-situ instrumentation we will be able to provide a urlique data set comprising chlorine and bromine source gases, including all the more important halocarbons (including CFCs, HCFCs, halons as well as chlorinated hydrocarbons and CH3Br), chlorine reservoir gases (CIONO2, HCI and HOCI), and the reactive chlorine and bromine oxides (CIO, BrO, OCIO) as well as aerosol surface areas, water vapour, actinic flux, and reactive nitrogen species. We propose to perform these measurements at mid and high latitudes of the northern hemisphere during three campaigns; a summer campaign in mid latitudes in 1998 for the observation of unperturbed conditions, a winter campaign at high latitudes in early 1999 for the observation of chemically processed airmasses, and a spring campaign from mid latitudes in the year 2000 for the investigation of possible transport of processed airmasses to mid latitudes. The project is a contribution to the THESOE campaign.
Three different payloads will be put together:
payload 1: cryogenic whole air sampler, ClO/BrO resonance fluorescence,Ly-a Hygrom. photometers, aerosol counter
payload 2: FTIR spectrometer, DOAS Spectrometer
payload 3: star pointing DOAS
In particular we want to investigate the following points:
1. To document the budget and the partitioning of bromine
and chlorine gases during the predicted peak of stratospheric chlorine both at high and mid latitudes of the Northern Hemisphere and monitor stratospheric trend of many halogen containing species.
2. Measure the most abundant bromine source gases and thus determine Bry. To observe BrO with two independent techniques and investigate bromine partitioning and possibly the role of bromine reservoir gases.
3. Determine Cly and by simultaneous measurement of HCI, CIONO2, OCIO and CIO investigate chlorine partitioning both at high and mid latitudes during different seasons.
4. Measure CIO, BrO and OCIO simultaneously with the actinic flux. This will allow us to investigate the partitioning between these three compounds and validate the halogen chemistry involved.
5. Night-time measurements of OCIO and NO2 will allow us to study the influence of nitrogen oxides on the night-time halogen chemistry, for example the formation of different bromine night-time reservoir species like BrONO2 and BrCI.
6. Investigate the heterogeneous activation of chlorine and possibly bromine species in the Arctic winter stratosphere, and possibly investigate the effects of Lee waves created by the Scandinavian mountains.
Funding SchemeCSC - Cost-sharing contracts
40801 Aire Sur L'adour