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| Titel |
Global peroxyacetyl nitrate (PAN) retrieval in the upper troposphere from limb emission spectra of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) |
| VerfasserIn |
N. Glatthor, T. Clarmann, H. Fischer, B. Funke, U. Grabowski, M. Höpfner, S. Kellmann, M. Kiefer, A. Linden, M. Milz, T. Steck, G. P. Stiller |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 7, no. 11 ; Nr. 7, no. 11 (2007-06-04), S.2775-2787 |
| Datensatznummer |
250005031
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| Publikation (Nr.) |
 copernicus.org/acp-7-2775-2007.pdf |
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| Zusammenfassung |
| We use limb emission spectra of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS)
onboard the ENVIronmental SATellite (ENVISAT) to derive the first global distribution of peroxyacetyl
nitrate (PAN) in the upper troposphere. PAN is generated in tropospheric air masses polluted by fuel
combustion or biomass burning and acts as a reservoir and carrier of NOx in the cold free
troposphere. PAN exhibits continuum-like broadband structures in the mid-infrared region and was
retrieved in a contiguous analysis window covering the wavenumber region 775–800 cm−1.
The interfering species CCl4, HCFC-22, H2O, ClONO2, CH3CCl3 and C2H2 were fitted
along with PAN, whereas pre-fitted profiles were used to model the contribution of other contaminants
like ozone. Sensitivity tests consisting in retrieval without consideration of PAN demonstrated
the existence of PAN signatures in MIPAS spectra obtained in polluted air masses. The analysed dataset
consists of 10 days between 4 October and 1 December 2003. This period covers the end of the biomass burning
season in South America and South and East Africa, in which generally large amounts of pollutants
are produced and distributed over wide areas of the southern hemispheric free troposphere. Indeed,
elevated PAN amounts of 200–700 pptv were measured in a large plume extending from Brasil
over the Southern Atlantic, Central and South Africa, the South Indian Ocean as far as Australia at
altitudes between 8 and 16 km. Enhanced PAN values were also found in a much more restricted area between
northern subtropical Africa and India. The most significant northern midlatitude PAN signal was detected
in an area at 8 km altitude extending from China into the Chinese Sea. The average mid and high
latitude PAN amounts found at 8 km were around 125 pptv in the northern, but only between 50 and 75 pptv
in the southern hemisphere. The PAN distribution found in the southern hemispheric tropics and subtropics
is highly correlated with the jointly fitted acetylene (C2H2), which is another pollutant
produced by biomass burning, and agrees reasonably well with the CO plume detected during end of September 2003
at the 275 hPa level (~10 km) by the Measurement of Pollution in the Troposphere (MOPITT)
instrument on the Terra satellite. Similar southern hemispheric PAN amounts were also observed by
previous airborne measurements performed in September/October 1992 and 1996 above the South Atlantic
and the South Pacific, respectively. |
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