ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-8-6707-2008 Direct observation of two dimensional trace gas distributions with an airborne Imaging DOAS instrument Heue K.-P. 1 Wagner T. 2 Broccardo S. P. 3 Walter D. 1 Piketh S. J. 3 Ross K. E. 4 Beirle S. 2 Platt U. 1 Institut für Umweltphysik (IUP), Universität Heidelberg, Heidelberg, Germany Max Planck Institut für Chemie, Mainz, Germany Climatology Research Group, University of the Witwatersrand, Johannesburg, South Africa Generation Environmental Management Department, Eskom Pty (Ltd), South Africa 21 11 2008 8 22 6707 6717 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/8/6707/2008/acp-8-6707-2008.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/8/6707/2008/acp-8-6707-2008.pdf

In many investigations of tropospheric chemistry information about the two dimensional distribution of trace gases on a small scale (e.g. tens to hundreds of metres) is highly desirable. An airborne instrument based on imaging Differential Optical Absorption Spectroscopy has been built to map the two dimensional distribution of a series of relevant trace gases including NO<sub>2</sub>, HCHO, C<sub>2</sub>H<sub>2</sub>O<sub>2</sub>, H<sub>2</sub>O, O<sub>4</sub>, SO<sub>2</sub>, and BrO on a scale of 100 m. <br><br> Here we report on the first tests of the novel aircraft instrument over the industrialised South African Highveld, where large variations in NO<sub>2</sub> column densities in the immediate vicinity of several sources e.g. power plants or steel works, were measured. The observed patterns in the trace gas distribution are interpreted with respect to flux estimates, and it is seen that the fine resolution of the measurements allows separate sources in close proximity to one another to be distinguished.

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