ACPD Atmospheric Chemistry and Physics Discussions ACPD 1680-7375 Copernicus GmbH Göttingen, Germany 10.5194/acpd-6-9459-2006 MAX-DOAS detection of glyoxal during ICARTT 2004 Sinreich R. 1 Volkamer R. 2 3 Filsinger F. 1 4 Frieß U. 1 Kern C. 1 Platt U. 1 Sebastián O. 1 Wagner T. 1 Institut für Umweltphysik, Universität Heidelberg, Heidelberg, Germany Massachusetts Institute of Technology, Cambridge, MA, USA now at: University of California, San Diego, La Jolla, CA, USA now at: Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany 26 09 2006 6 5 9459 9481 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-discuss.net/6/9459/2006/acpd-6-9459-2006.html The full text article is available as a PDF file from http://www.atmos-chem-phys-discuss.net/6/9459/2006/acpd-6-9459-2006.pdf

The direct detection of glyoxal (CHOCHO), the smallest &alpha;-dicarbonyl, in the open atmosphere by active differential optical absorption spectroscopy (DOAS) has recently been demonstrated (Volkamer et al., 2005a) and triggered the very recent successful detection of CHOCHO from space (Kurosu et al., 2005; Wittrock et al., 2006; Beirle et al., 2006). Here we report the first detection of CHOCHO by passive multi axis differential optical absorption spectroscopy (MAX-DOAS). CHOCHO and NO<sub>2</sub> slant column measurements were conducted at MIT, Cambridge, USA, and on board the research vessel Ron Brown in the Gulf of Maine as part of the International Consortium for Atmospheric Research on Transport and Transformation (ICARTT) 2004 campaign. For a day with nearly clear sky conditions, radiative transfer modeling was employed to derive diurnal CHOCHO mixing ratios for both sites. CHOCHO mixing ratios at MIT varied from 40 to 120 ppt, with peak values observed around noon. Mixing ratios over the Gulf of Maine were found to be up to 3 times larger than at MIT. The CHOCHO-to-NO<sub>2</sub>ratio at MIT was <0.03, and enhancements of this ratio by up to two orders of magnitude were found over the Gulf of Maine. This paper focuses on the instrumental aspects involved with MAX-DOAS measurements of CHOCHO.