ACPD Atmospheric Chemistry and Physics Discussions ACPD 1680-7375 Copernicus GmbH Göttingen, Germany 10.5194/acpd-9-865-2009 Mobile mini-DOAS measurement of the emission of NO<sub>2</sub> and HCHO from Mexico City Johansson M. 1 Rivera C. 1 de Foy B. 2 Lei W. 3 4 Song J. 3 4 Zhang Y. 1 Galle B. 1 Molina L. 3 4 Chalmers University of Technology, Göteborg, Sweden Saint Louis University, St Louis, MO, USA Molina Center for Energy and the Environment, La Jolla, CA, USA Massachusetts Institute of Technology, Cambridge, MA, USA 12 01 2009 9 1 865 882 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/9/865/2009/acpd-9-865-2009.html The full text article is available as a PDF file from http://www.atmos-chem-phys-discuss.net/9/865/2009/acpd-9-865-2009.pdf

We here present the result of one mobile measurement using two ground based zenith viewing Differential Optical Absorption Spectroscopy (DOAS) instrument performed in a cross-section of the plume from the MCMA on the 10 March 2006 as part of the MILAGRO field campaign. The two instruments operated in the UV and the visible wavelength region respectively and have been used to derive the differential vertical columns of HCHO and NO<sub>2</sub> above the measurement route. <br></br> Using a mass-averaged wind speed and wind direction from the WRF model the instantaneous flux of HCHO and NO<sub>2</sub> has been calculated from the two measurements and the results compared to the CAMx chemical model. The calculated flux through the measured cross-section was 1.9 (1.5–2.2) kg/s of HCHO and 4.4 (4.0–5.0) kg/s of NO<sub>2</sub> using the UV instrument and 3.66 (3.63–3.73) kg/s of NO<sub>2</sub> using the visible light instrument. The comparison with modeled values from CAMx shows a good agreement for the outflow of both NO<sub>2</sub> and HCHO at this occasion.

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