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| Titel |
Simulations of atmospheric OH, O3 and NO3 reactivities within and above the boreal forest |
| VerfasserIn |
D. Mogensen, R. Gierens, J. N. Crowley, P. Keronen, S. Smolander, A. Sogachev, A. C. Nölscher, L. Zhou, M. Kulmala  , M. J. Tang, J. Williams, M. Boy |
| 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 ; 15, no. 7 ; Nr. 15, no. 7 (2015-04-15), S.3909-3932 |
| Datensatznummer |
250119626
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| Publikation (Nr.) |
 copernicus.org/acp-15-3909-2015.pdf |
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| Zusammenfassung |
| Using the 1-D atmospheric chemistry transport model SOSAA, we have
investigated the atmospheric reactivity of a boreal forest ecosystem
during the HUMPPA-COPEC-10 campaign (summer 2010, at SMEAR~II in
southern Finland). For the very first time, we present vertically
resolved model simulations of the NO3 and
O3 reactivity (R) together with the modelled and measured
reactivity of OH. We find that OH is the most reactive
oxidant (R ∼ 3 s-1) followed by NO3 (R ∼
0.07 s-1) and O3 (R ∼ 2 ×
10-5s-1). The missing OH reactivity was found to be
large in accordance with measurements (∼ 65%) as would
be expected from the chemical subset described in the model. The
accounted OH radical sinks were inorganic compounds (∼
41%, mainly due to reaction with CO), emitted
monoterpenes (∼ 14%) and oxidised biogenic volatile
organic compounds (∼ 44%). The missing reactivity is
expected to be due to unknown biogenic volatile organic compounds
and their photoproducts, indicating that the true main sink of
OH is not expected to be inorganic compounds. The
NO3 radical was found to react mainly with primary emitted
monoterpenes (∼ 60%) and inorganic compounds (∼
37%, including NO2). NO2 is, however, only
a temporary sink of NO3 under the conditions of the campaign (with typical temperatures of 20–25 °C)
and does not affect the NO3 concentration. We discuss the
difference between instantaneous and steady-state reactivity and
present the first boreal forest steady-state lifetime of NO3
(113 s). O3 almost exclusively reacts with
inorganic compounds (∼ 91%, mainly NO, but also
NO2 during night) and less with primary emitted
sesquiterpenes (∼ 6%) and monoterpenes (∼
3%). When considering the concentration of the oxidants
investigated, we find that OH is the oxidant that is capable
of removing organic compounds at a faster rate during daytime, whereas
NO3 can remove organic molecules at a faster rate during night-time.
O3 competes with OH and NO3 during a short period
of time in the early morning (around 5 a.m. local time) and in the evening (around 7–8 p.m.).
As part of this study, we developed
a simple empirical parameterisation for conversion of measured
spectral irradiance into actinic flux. Further, the meteorological
conditions were evaluated using radiosonde observations and ground-based measurements. The overall vertical structure of the boundary
layer is discussed, together with validation of the surface energy
balance and turbulent fluxes. The sensible heat and momentum fluxes
above the canopy were on average overestimated, while the latent
heat flux was underestimated. |
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