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| Titel |
Constraining the concentration of the hydroxyl radical in a stratocumulus-topped marine boundary layer from sea-to-air eddy covariance flux measurements of dimethylsulfide |
| VerfasserIn |
M. Yang, B. W. Blomquist, B. J. Huebert |
| 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 ; 9, no. 23 ; Nr. 9, no. 23 (2009-12-07), S.9225-9236 |
| Datensatznummer |
250007788
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| Publikation (Nr.) |
 copernicus.org/acp-9-9225-2009.pdf |
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| Zusammenfassung |
| The hydroxyl radical (OH) is an important oxidant in the troposphere due to
its high reactivity and relative abundance. Measuring the concentration of
OH in situ, however, is technically challenging. Here we present a simple
method of estimating an OH-equivalent oxidant concentration ("effective
OH") in the marine boundary layer (MBL) from the mass balance of
dimethylsulfide (DMS). We use shipboard eddy covariance measurements of the
sea-to-air DMS flux from the Vamos Ocean-Cloud-Atmosphere-Land Study
Regional Experiment (VOCALS-REx) in October and November of 2008. The
persistent stratocumulus cloud-cover off the west coast of South America and
the associated strong inversion between MBL and the free troposphere (FT)
greatly simplify the dynamics in this region and make our budget estimate
possible. From the observed diurnal cycle in DMS concentration, the
nighttime entrainment velocity at the inversion is estimated to be
4 mm s−1. We calculate 1.4(±0.2)×106
OH molecules cm−3
from the DMS budget, which represents a monthly effective concentration and
is well within the range of previous estimates. Furthermore, when linearly
proportioned according to the intensity of solar flux, the resultant diel OH
profile, together with DMS surface and entrainment fluxes, enables us to
accurately replicate the observed diurnal cycle in DMS (correlation
coefficient over 0.9). The nitrate radical (NO3) is found to have
little contribution to DMS oxidation during VOCALS-REx. An upper limit
estimate of 1 pptv of bromine oxide radical (BrO) would account for 30%
of DMS oxidation and lower the OH concentration to
1.0)×106 OH molecules cm−3. Our
effective OH estimate includes the oxidation of DMS by such radicals. |
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