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| Titel |
Summertime total OH reactivity measurements from boreal forest during HUMPPA-COPEC 2010 |
| VerfasserIn |
A. C. Nölscher, J. Williams, V. Sinha, T. Custer, W. Song, A. M. Johnson, R. Axinte, H. Bozem, H. Fischer, N. Pouvesle, G. Phillips, J. N. Crowley, P. Rantala, J. Rinne, M. Kulmala  , D. Gonzales, J. Valverde-Canossa, A. Vogel, T. Hoffmann, H. G. Ouwersloot, 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 ; 12, no. 17 ; Nr. 12, no. 17 (2012-09-13), S.8257-8270 |
| Datensatznummer |
250011445
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| Publikation (Nr.) |
 copernicus.org/acp-12-8257-2012.pdf |
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| Zusammenfassung |
| Ambient total OH reactivity was measured at the Finnish boreal forest station
SMEAR II in Hyytiälä (Latitude 61°51' N; Longitude
24°17' E) in July and August 2010 using the Comparative Reactivity Method (CRM). The
CRM – total OH reactivity method – is a direct, in-situ determination of the
total loss rate of hydroxyl radicals (OH) caused by all reactive species in
air. During the intensive field campaign HUMPPA-COPEC 2010
(Hyytiälä United Measurements of
Photochemistry and Particles in Air –
Comprehensive Organic Precursor Emission
and Concentration study) the total OH reactivity was monitored both
inside (18 m) and directly above the forest canopy (24 m) for the first time.
The comparison between these two total OH reactivity measurements, absolute
values and the temporal variation have been analyzed here. Stable boundary
layer conditions during night and turbulent mixing in the daytime induced low
and high short-term variability, respectively. The impact on total OH
reactivity from biogenic emissions and associated photochemical products was
measured under "normal" and "stressed" (i.e. prolonged high temperature)
conditions. The advection of biomass burning emissions to the site caused a
marked change in the total OH reactivity vertical profile. By comparing the
OH reactivity contribution from individually measured compounds and the
directly measured total OH reactivity, the size of any unaccounted for or
"missing" sink can be deduced for various atmospheric influences. For
"normal" boreal conditions a missing OH reactivity of 58%, whereas for
"stressed" boreal conditions a missing OH reactivity of 89% was
determined. Various sources of not quantified OH reactive species are
proposed as possible explanation for the high missing OH reactivity. |
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