Descartes

Updated 2003-06-19

Objectives 1. To develop the measurement technique further, providing more accurate measurements and extend the method to a larger number of trace species 2. To monitor the presence of CFC:s and other longlived anthropogenic tracers in the stratosphere 3. To use long-lived anthropogenic species as tracers of atmospheric motion, in particular for comparison with atmospheric models Reserarchers: Descartes is a joint research programme currently involving N.R.P Harris and J.A. Pyle, Centre for Atmospheric Science at the Department of Chemistry, University of Cambridge, U.K., and Hans Nilsson and Johan Arvelius, Swedish Institute of Space Physics, Kiruna, Sweden

This is not a National Implementation Plan (NIP) project

Time frame

Status
Ongoing
Project time span
1996 - 2020
Data collection
1998 - 2002
Data processing
1998 - 2003
Data reporting
1998 - 2003

Contact information

Contact person
Hans Nilsson
Address
Swedish Institute of Space Physics Box 812 981 28 Kiruna Sweden
Phone
+46 980 79127
Fax
+46 980 79050
Email
es.fri@enah
Other project contacts
Susanne Roslin Johan Arvelius

Parameters and Media

Parameter groups measured/observed/modelled
Other metals/elements
Media sampled/studied/modelled
Air/aerosol

Geography

Regions studied
Arctic, Circumpolar
Fennoscandia
Norway
Scandinavia
Sweden
Other areas
Arctic polar vortex

Data availability

Are data archived or planned to be archived at an AMAP Thematic Data Centre?
no
If no (or only part of data are reported to a TDC), where and how are (other) data stored?
Flight profiles from all flights are calculated and available from the THESEO database. Data can be provided on request after an agreement on the use of the data has been made.
References to key publications (or planned publications) and data reports
http://www.irf.se/MRIatmos/projects/descartes/publications.html
Samples/specimens archived in specimen banks?
No

Methods & Procedures

Procedures and methodology used for, e.g., sampling and sample storage, sample pretreatment, extraction and analysis, including which laboratories are involved, references to methods employed, etc.

General principle. Samples are taken by pumping air through a sample tube containing an adsorbent (Carboxen 569). Samples are taken at predefined atmospheric pressure levels (which can be programmed for each flight). The flow through the sample tube is measured and the average flow stored in the onboard computer memory. The sample tubes are mounted on a 16 position valve, and 15 of those sample tubes are used for samples. The sixteenth is a 'waiting position' used while passing up and down through the troposphere, to prevent pollution of the stratospheric samples. A bottle containing a standard of trace species can be used for taking standard samples at different pressure levels for calibration and instrument performance monitoring. To prevent pollution of the samples the sample tubes and the 16 position valve are kept in an airtight 'sample box', which is kept under inert nitrogen atmosphere at about 100 hPa above ambient pressure. Analysis. The trapped trace gases are thermally desorbed by heating the sample tube to about 200°C. The heating is done in a number of 5 second cycles. For each heating cycle the desorbed trace gases are passed into a gas chromatograph (GC) using an electron capture detector (ECD). The setup is described in Danis et al. [1995]. The response of the ECD is monitored by taking standard samples with tropospheric concentrations of N2O, CFC-11, CFC-12 and CFC-113 between the analysis of each sample tube. Calibration of the sample tube - GC system is achieved by passing known amounts of the above mentioned gas standard through the sample tubes in the laboratory, and then using the standard analysis procedure for stratospheric samples. Initial investigations indicate that the ECD response is non-linear, and most of the uncertainty in the quantitative estimate of CFC-11 and CFC-12 is due to uncertainties in the calibration of the ECD response (Stacey [1996]).

Additional Information

Is this a bi- AND multi-lateral project (i.e. a project involving cooperation between different countries)?
Yes
Other institutes involved in the project

University of Cambridge, Centre for Atmospheric Science at the Department of Chemistry

Is this project reporting to other organizations/programmes?

NILU database within the EU funded Theseo projects

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