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| Titel |
Bromocarbons in the tropical marine boundary layer at the Cape Verde Observatory – measurements and modelling |
| VerfasserIn |
L. M. O'Brien, N. R. P. Harris, A. D. Robinson, B. Gostlow, N. Warwick, X. Yang, J. A. Pyle |
| 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. 22 ; Nr. 9, no. 22 (2009-11-30), S.9083-9099 |
| Datensatznummer |
250007778
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| Publikation (Nr.) |
 copernicus.org/acp-9-9083-2009.pdf |
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| Zusammenfassung |
| A new gas chromatograph was used to make measurements of halocarbons at the
Cape Verde observatory during late May and early June 2007. The instrument
demonstrated its potential for long-term autonomous measurements. Bromoform
(CHBr3) exhibits the most variability of all the halocarbons observed,
ranging from a background concentration of about 4 ppt to a maximum of >40 ppt
during the course of the measurement period. CH2Br2 correlates
well with bromoform, suggesting a common regional source. Methyl iodide does
not correlate with these bromocarbons, with base levels of around 1–2 ppt
and some periods of much higher mixing ratios. Using published bromocarbon
emission rates, our chemical transport model studies, presented here, do not
reproduce the observations. Local emission magnitudes and
CHBr3:CH2Br2 ratios must be increased more in line with the
recent observations of Yokouchi et al. (2005) to improve the model to
measurement comparison. Even when the model reproduces the observed
bromocarbons, modelled BrO is much less than recent tropical observations
(Read et al., 2008). A sea salt source seems the likely explanation. When
high BrO is reproduced, the model agrees much better with the observed ozone
changes, including diurnal variation, during the measurement period but it
is suggested that a representation of iodine chemistry in the model is also
required. |
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