 |
| Titel |
Impact of the deep convection of isoprene and other reactive trace species on radicals and ozone in the upper troposphere |
| VerfasserIn |
E. C. Apel, J. R. Olson, J. H. Crawford, R. S. Hornbrook, A. J. Hills, C. A. Cantrell, L. K. Emmons, D. J. Knapp, S. Hall, R. L. Mauldin III, A. J. Weinheimer, A. Fried, D. R. Blake, J. D. Crounse, J. M. St. Clair, P. O. Wennberg, G. S. Diskin, H. E. Fuelberg, A. Wisthaler, T. Mikoviny, W. Brune, D. D. Riemer |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 12, no. 2 ; Nr. 12, no. 2 (2012-01-27), S.1135-1150 |
| Datensatznummer |
250010552
|
| Publikation (Nr.) |
 copernicus.org/acp-12-1135-2012.pdf |
|
|
|
|
|
| Zusammenfassung |
| Observations of a comprehensive suite of inorganic and organic trace gases,
including non-methane hydrocarbons (NMHCs), halogenated organics and
oxygenated volatile organic compounds (OVOCs), obtained from the NASA DC-8
over Canada during the ARCTAS aircraft campaign in July 2008 illustrate that
convection is important for redistributing both long- and short-lived
species throughout the troposphere. Convective outflow events were
identified by the elevated mixing ratios of organic species in the upper
troposphere relative to background conditions. Several dramatic events were
observed in which isoprene and its oxidation products were detected at
hundreds of pptv at altitudes higher than 8 km. Two events are studied in
detail using detailed experimental data and the NASA Langley Research Center
(LaRC) box model. One event had no lightning NOx (NO + NO2)
associated with it and the other had substantial lightning NOx (LNOx > 1 ppbv). When convective storms transport isoprene from the boundary
layer to the upper troposphere and no LNOx is present, OH is reduced
due to scavenging by isoprene, which serves to slow the chemistry, resulting
in longer lifetimes for species that react with OH. Ozone and PAN production
is minimal in this case. In the case where isoprene is convected and
LNOx is present, there is a large effect on the expected ensuing
chemistry: isoprene exerts a dominant impact on HOx and
nitrogen-containing species; the relative contribution from other species to
HOx, such as peroxides, is insignificant. The isoprene reacts quickly,
resulting in primary and secondary products, including formaldehyde and
methyl glyoxal. The model predicts enhanced production of alkyl nitrates
(ANs) and peroxyacyl nitrate compounds (PANs). PANs persist because of the
cold temperatures of the upper troposphere resulting in a large change in
the NOx mixing ratios which, in turn, has a large impact on the
HOx chemistry. Ozone production is substantial during the first few
hours following the convection to the UT, resulting in a net gain of
approximately 10 ppbv compared to the modeled scenario in which LNOx is
present but no isoprene is present aloft. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|