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Improved ground-based off-axis DOAS measurements of BrO, NO2 and IO

Multi- Axis- (MAX-) DOAS, a measurement technique that has become more and more popular in recent years, has the potential to discriminate between tropospheric and stratospheric absorbers. By observing scattered light not only from the zenith but also from sky close to the horizon, a long light path through the lowermost atmospheric layers and a strongly increased sensitivity to trace gases located
close to the surface can be achieved.

During the QUILT project period, MAX-DOAS measurements of atmospheric trace gases have been performed at various locations, covering the Arctic, the northern mid- latitudes, the tropics and Antarctica, as well as 4 ship cruises from Bremerhaven to Antarctica onboard the Polarstern research vessel. In addition, the owners of this result particapated in the NDSC intercomparison in Andoya in February 2003 and in two campaigns within the FORMAT project with a MAX-DOAS setup.

The derived data sets illustrate, that MAX-DOAS is able to:
- Measure halogen oxides in the boundary layer.
- Measure local pollution, e.g. NO2 in the Arctic.
- Give information on the aerosol extinction profiles and the optical properties of aerosol.

In summary, Multi-Axis DOAS measurements are a promising tool for continuous measurements of several tropospheric species such as NO2, BrO, SO2, HCHO, and O3.

Quantitative analysis of the measurements depends on a number of parameters in the radiative transfer, and models such as those described in the project are now in a position to include all these factors with the necessary accuracy.

In the near future other applications for off-axis or MAX-DOAS observations are likely:
- Monitoring of air pollution;
- Monitoring of volcanoes;
- Tomography of urban areas.

It is also expected, that advances in software development raises new applications. While radiative transfer models are available to interpret MAX-DOAS data, the algorithms to derive vertical profiles of trace gases are still under development.

More information on the QUILT project can be found at:

Informations connexes

Reported by

Institute of Environmental Physics, University of Bremen
Otto-Hahn-Allee 1
28359 Bremen
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