POLAR6 - CO and CO2/H2O measurements

During the NETCARE 2014 campaign in Resolute Bay, CO and CO2/H2O measurements were performed by the University of Mainz. For CO a fast CO monitor from Aero-Laser was used (we thank the Max Planck Institute for Chemistry  Mainz for the possibility to use the CO instrument). The measurement method of the AL5002 is based on the fluorescence of CO in the VUV at 150 nm. The fluorescence light in the wavelength range between 160 nm and 190 nm is detected by a VUV photomultiplier followed by a fast counter.  CO2 and water vapor are measured with a modified LI-7200 from Licor Biosciences. The modifications include a pressure and flow control of the instrument as well as the implementation of in-situ calibrations during the flights. The LI-7200 optical source emits infrared light through a chopper filter wheel and the enclosed sample path to a temperature-controlled lead selenide detector. Some of the infrared light is absorbed by carbon dioxide and water vapor in the sample path, and the ratio of absorption to a reference is used to compute density of the gases.

The instrument as well as a supply gas for the UV lamp of the CO analyzer are installed in a rack together with the AWI UHSAS and SP2 instrument. An additional bottom plate contains calibration gas and pumps for the trace gas instruments.

The measurements of CO, CO2 and water vapor allow us to characterize the structure of the arctic boundary layer. This includes spatial as well as temporal variations due to different surface or synoptic conditions. In addition, long range transport from lower latitudes can be identified by different values of CO and CO2 or sources of pollution can be identified. On several flights a pollution plume with enhanced CO mixing ratios at higher altitudes (>3000ft) was observed. Most likely these air mases are influenced by biomass burning events in the North West Territories. In contrast the last part of the campaign was dedicated to ship emission measurements. Most of these plume encounters were observable in CO2 such that emission indices of other tracers (NOx, BC, particle number) can be inferred. Both pollution sources in general show different characteristics with respect to trace gas concentrations.


-Heiko Bozem and Peter Hoor, University Mainz, NETCARE Collaborators


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