Participation to the POLARCAT activity

The POLARCAT-France spring campaign took place between 30 March and 11 April 2008 as part of the POLARCAT international research activity (Polar Study using Aircraft, Remote Sensing, Surface Measurements and Models, of Climate, Chemistry, Aerosols, and Transport), in the framework of the International Polar Year (IPY).

Based in Kiruna, Sweden, the Safire ATR-42 aircraft performed twelve scientific flights between continental Norway and Svalbard. Scientific objectives of the campaign included the study of pollution transport, aerosol/cloud interactions and satellite validation.

The Airborne Limb Scanning DOAS (ALS-DOAS) was developed at the Belgian Institute for Space Aeronomy (BIRA-IASB) and first used during the POLARCAT campaign. It records limb-scattered sky light spectra at several angles around the horizon, following the Multi-axis DOAS principle.

Several tropospheric molecules absorb light in the spectral range of our instrument and thus are potentially detectable: O₃, NO₂, HCHO, CHOCHO, O₄, IO and BrO. In the POLARCAT data, we have focused on O₄ and NO₂ measurements, which were most clearly identified during the campaign.

The O₄ measurements were used to retrieve the aerosol extinction and used as an input for the aerosol loading in the retrieval of NO₂. Both retrievals are based on a maximum a posteriori approach. We have compared a gaussian a priori with a lognormal one, which constrains the solution to positive values. The latter yields, in our cases, extinctions which are closer to independently measured size distributions.

The measured vertical distributions are interpreted from CO and ozone in-situ measurements complemented by back-trajectories.

The NO₂ layer at 4 km altitude observed on 9 April 2009 seems to have been directly transported from central Europe with CO and aerosols.

On 8 April 2009, aerosols and NO₂ are seen in the boundary layer and seem to originate from metal smelters and industry near Nikel on the Kola peninsula. The free troposphere is influenced by a stratospheric intrusion.

Publications

Merlaud, A., Van Roozendael, M., Theys, N., Fayt, C., Hermans, C., Quennehen, B., Schwarzenboeck, A., Ancellet, G., Pommier, M., Pelon, J., Burkhart, J., Stohl, A., and De Mazière, M.: Airborne DOAS measurements in Arctic: vertical distributions of aerosol extinction coefficient and NO₂ concentration, Atmos. Chem. Phys., 11, 9219-9236, doi:10.5194/acp-11-9219-2011

Acknowledgements and links

This work was supported by the Belgian Federal Science Policy (contract MO/35/028). The installation of the ALS-DOAS in the Safire ATR-42 and our participation to POLARCAT were funded by EUFAR through the POLUVIS project.

BELSPO	EUFAR	SAFIRE

Contact

For more information, please contact : Alexis Merlaud or Michel Van Roozendael