1Spectroscopie de l'atmosphère, Chimie Quantique et Photophysique, Univ. Libre de Bruxelles (U.L.B.), Brussels, Belgium
2Service d'Aéronomie/Institut Pierre-Simon Laplace, CNRS, Université Pierre et Marie Curie-Paris 6, France
3NASA Langley Research Center, Mail Stop 401A, Hampton, VA 23681-2199, USA
4Earth Observation Science, Space Research Centre, Department of Physics & Astronomy, University of Leicester, University Road, Leicester, LE1 7RH, UK
5Laboratoire des Sciences du Climat et de l'Environnement (LSCE)/Institut Pierre-Simon Laplace, CEA-CNRS, 91191 Gif-sur-Yvette CEDEX, France
6Department of Chemistry, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada
7Department of Chemistry, University of York, Heslington, York YO10 5DD, UK
Abstract. In the course of our study of the upper tropospheric composition with the infrared Atmospheric Chemistry Experiment – Fourier Transform Spectrometer (ACE–FTS), we found an occultation sequence that on 8 October 2005, sampled a remarkable plume near the east coast of Tanzania. Model simulations of the CO distribution in the Southern hemisphere are performed for this period and they suggest that the emissions for this event likely originated from a nearby forest fire, after which the plume was transported from the source region to the upper troposphere. Taking advantage of the very high signal-to-noise ratio of the ACE–FTS spectra over a wide wavenumber range (750–4400 cm−1), we present in-depth analyses of the chemical composition of this plume in the middle and upper troposphere, focusing on the measurements of weakly absorbing pollutants. For this specific biomass burning event, we report simultaneous observations of an unprecedented number of organic species. Measurements of C2H4 (ethene), C3H4 (propyne), H2CO (formaldehyde), C3H6O (acetone) and CH3COO2NO2 (peroxyacetylnitrate, abbreviated as PAN) are the first reported detections using infrared occultation spectroscopy from satellites. Based on the lifetime of the emitted species, we discuss the photochemical age of the plume and also report, whenever possible, the enhancement ratios relative to CO.