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| Titel |
Surface and boundary layer exchanges of volatile organic compounds, nitrogen oxides and ozone during the GABRIEL campaign |
| VerfasserIn |
L. Ganzeveld, G. Eerdekens, G. Feig, H. Fischer, H. Harder, R. Königstedt, D. Kubistin, M. Martinez, F. X. Meixner, H. A. Scheeren, V. Sinha, D. Taraborrelli, J. Williams, J. Vilà-Guerau de Arellano, J. Lelieveld  |
| 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 ; 8, no. 20 ; Nr. 8, no. 20 (2008-10-27), S.6223-6243 |
| Datensatznummer |
250006424
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| Publikation (Nr.) |
 copernicus.org/acp-8-6223-2008.pdf |
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| Zusammenfassung |
| We present an evaluation of sources, sinks and turbulent transport of
nitrogen oxides, ozone and volatile organic compounds (VOC) in the boundary
layer over French Guyana and Suriname during the October 2005 GABRIEL
campaign by simulating observations with a single-column chemistry and
climate model (SCM) along a zonal transect. Simulated concentrations of
O3 and NO as well as NO2 photolysis rates over the forest agree
well with observations when a small soil-biogenic NO emission flux was
applied. This suggests that the photochemical conditions observed during
GABRIEL reflect a pristine tropical low-NOx regime. The SCM uses a
compensation point approach to simulate nocturnal deposition and daytime
emissions of acetone and methanol and produces daytime boundary layer mixing
ratios in reasonable agreement with observations. The area average isoprene
emission flux, inferred from the observed isoprene mixing ratios and
boundary layer height, is about half the flux simulated with commonly
applied emission algorithms. The SCM nevertheless simulates too high
isoprene mixing ratios, whereas hydroxyl concentrations are strongly
underestimated compared to observations, which can at least partly explain
the discrepancy. Furthermore, the model substantially overestimates the
isoprene oxidation products methlyl vinyl ketone (MVK) and methacrolein
(MACR) partly due to a simulated nocturnal increase due to isoprene
oxidation. This increase is most prominent in the residual layer whereas in
the nocturnal inversion layer we simulate a decrease in MVK and MACR mixing
ratios, assuming efficient removal of MVK and MACR. Entrainment of residual
layer air masses, which are enhanced in MVK and MACR and other isoprene
oxidation products, into the growing boundary layer poses an additional sink
for OH which is thus not available for isoprene oxidation. Based on these
findings, we suggest pursuing measurements of the tropical residual layer
chemistry with a focus on the nocturnal depletion of isoprene and its
oxidation products. |
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