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Retrieval of peroxyacetylnitrate (PAN) in the upper troposphere from MIPAS level-1B spectra

Norbert Glatthor(1), Thomas von Clarmann(2), Herbert Fischer(1), Bernd Funke(3), Udo Grabowski(1), Michael Hoepfner(1), Sylvia Kellmann(1), Michael Kiefer(1), Andrea Linden(4), Mathias Milz(4), Tilman Steck(4) and Gabriele Stiller(4)

(1) Forschungszentrum Karlsruhe, IMK, Postfach 3640, 76021 Karlsruhe, Germany
(2) Forschungszentrum Karlsruhe, Postfach 3640, 76021 Karlsruhe, Germany
(3) Instituto de Astrofisica de Andalucia, CSIC, Apartado Postal 3004 , 18080 Granada, Spain
(4) Forschungszentrum Karlsruhe, IMK/FZK, Postfach 3640, 76021 Karlsruhe, Germany

Abstract

Peroxyacetylnitrate (PAN) is produced in polluted atmospheres and thus an indicator of photochemical smog. When it is destroyed, NO2 is released. Its thermal decomposition rate is highly temperature dependent, ranging from 1 h at 298 K to 148 days at 250 K. However, due to photolysis its mean lifetime is restricted to 3 months. Because of its temperature sensitivity it can only be transported over a few hundred kilometres in the lower troposphere, but over distances of more than 10000 km in each hemisphere in the cold upper troposphere. Thus it serves as a reservoir and carrier of NOx via this region.

PAN has only weak broad-band signatures in the mid-infrared and requires a very accurate retrieval. At IMK, PAN retrievals were performed in the wavenumber region 775-800 cm-1, using new spectrocopic data provided by the University of Leicester. Besides PAN, all other major species contributing to the spectral radiance were also fitted. We present the retrieval method and first results obtained for the period October/November 2003.

 

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry