Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 6 1 2006 10.5194/acpd-6-493-2006 http://www.atmos-chem-phys-discuss.net/6/493/2006/ http://www.atmos-chem-phys-discuss.net/6/493/2006/acpd-6-493-2006.html http://www.atmos-chem-phys-discuss.net/6/493/2006/acpd-6-493-2006.pdf 493 517 2006-01-10 NO<sub>2</sub> Profile Retrieval using airborne multi axis UV-visible skylight absorption measurements over central Europe M. Bruns S. A. Buehler J. P. Burrows A. Richter A. Rozanov P. Wang K.-P. Heue U. Platt I. Pundt T. Wagner Institute of Environmental Physics, University of Bremen, P.O. Box 33 04 40, 28359 Bremen, Germany Institute of Environmental Physics, University of Heidelberg, Im Neuenheimer Feld 229, 69120 Heidelberg, Germany now at: Climate Research and Seismology Department, Royal Netherlands Meteorological Institute (KNMI), P.O. Box 201, 3730 AE De Bilt, The Netherlands A recent development in ground-based remote sensing of atmospheric constituents by UV/visible absorption measurements of scattered light is the simultaneous use of several directions with small elevation angles in addition to the traditional zenith-sky pointing. The different light paths through the atmosphere enable the vertical distribution of some atmospheric absorbers such as NO<sub>2</sub>, BrO or O<sub>3</sub> to be retrieved. <br><br> In this study, the amount of profile information that can be retrieved from such measurements on aircraft is investigated for the trace gas NO<sub>2</sub>. A Sensitivity study on synthetic data is performed for a combination of four lines of sight (LOS) (0&deg; (nadir), 88&deg;, 92&deg;, and 180&deg; (zenith)) and three wavelength regions [center wavelengths: 362.5&nbsp;nm, 437.5&nbsp;nm, and 485.0&nbsp;nm]. This investigation demonstrates the potential of this LOS/wavelengths setup to retrieve a significant amount of profile information from <B>a</B>irborne <B>m</B>ulti<B>ax</B>is <B>d</B>ifferential <B>o</B>ptical <B>a</B>bsorption <B>s</B>pectrometer (AMAXDOAS) measurements with a vertical resolution of 3.0 to 4.5&nbsp;km in the lower troposphere and 2.0 to 3.5&nbsp;km near flight altitude. Above 13&nbsp;km the profile information content of AMAXDOAS measurements is sparse. <br><br> Further, retrieved profiles with a significant amount (up to 3.2&nbsp;ppbv) of NO<sub>2</sub> in the boundary layer over the Po-valley (Italy) are presented. Airborne multiaxis measurements are thus a promising tool for atmospheric studies in the troposphere.