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| Titel |
Reactive Halogens in the Marine Boundary Layer (RHaMBLe): the tropical North Atlantic experiments |
| VerfasserIn |
J. D. Lee, G. McFiggans, J. D. Allan, A. R. Baker, S. M. Ball, A. K. Benton, L. J. Carpenter, R. Commane, B. D. Finley, M. Evans, E. Fuentes, K. Furneaux, A. Goddard, N. Good, J. F. Hamilton, D. E. Heard, H. Herrmann, A. Hollingsworth, J. R. Hopkins, T. Ingham, M. Irwin, C. E. Jones, R. L. Jones, W. C. Keene, M. J. Lawler, S. Lehmann, A. C. Lewis, M. S. Long, A. Mahajan, J. Methven, S. J. Moller, K. Müller, T. Müller, N. Niedermeier, S. O'Doherty, H. Oetjen, J. M. C. Plane, A. A. P. Pszenny, K. A. Read, A. Saiz-Lopez, E. S. Saltzman, R. Sander, R. Glasow, L. Whalley, A. Wiedensohler, D. Young |
| 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 ; 10, no. 3 ; Nr. 10, no. 3 (2010-02-01), S.1031-1055 |
| Datensatznummer |
250008028
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| Publikation (Nr.) |
 copernicus.org/acp-10-1031-2010.pdf |
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| Zusammenfassung |
The NERC UK SOLAS-funded Reactive Halogens in the Marine
Boundary Layer (RHaMBLe) programme comprised three field
experiments. This manuscript presents an overview of the
measurements made within the two simultaneous remote
experiments conducted in the tropical North Atlantic in May
and June 2007. Measurements were made from two mobile and one
ground-based platforms. The heavily instrumented cruise D319
on the RRS Discovery from Lisbon, Portugal to São Vicente,
Cape Verde and back to Falmouth, UK was used to characterise
the spatial distribution of boundary layer components likely
to play a role in reactive halogen chemistry. Measurements
onboard the ARSF Dornier aircraft were used to allow the
observations to be interpreted in the context of their
vertical distribution and to confirm the interpretation of
atmospheric structure in the vicinity of the Cape Verde
islands. Long-term ground-based measurements at the Cape Verde
Atmospheric Observatory (CVAO) on São Vicente were
supplemented by long-term measurements of reactive halogen
species and characterisation of additional trace gas and
aerosol species during the intensive experimental period.
This paper presents a summary of the measurements made within
the RHaMBLe remote experiments and discusses them in their
meteorological and chemical context as determined from these
three platforms and from additional meteorological
analyses. Air always arrived at the CVAO from the North East
with a range of air mass origins (European, Atlantic and North
American continental). Trace gases were present at stable and
fairly low concentrations with the exception of a slight
increase in some anthropogenic components in air of North
American origin, though NOx mixing ratios during this
period remained below 20 pptv (note the non-IUPAC adoption
in this manuscript of pptv and ppbv, equivalent to
pmol mol−1 and nmol mol−1 to reflect common
practice). Consistency with these air mass classifications is
observed in the time series of soluble gas and aerosol composition
measurements, with additional identification of periods of
slightly elevated dust concentrations consistent with the
trajectories passing over the African continent. The CVAO is shown
to be broadly representative of the wider North Atlantic marine
boundary layer; measurements of NO, O3 and black
carbon from the ship are consistent with a clean Northern
Hemisphere marine background. Aerosol composition measurements do
not indicate elevated organic material associated with clean
marine air. Closer to the African coast, black carbon and
NO levels start to increase, indicating greater
anthropogenic influence. Lower ozone in this region is
possibly associated with the increased levels of measured
halocarbons, associated with the nutrient rich waters of the
Mauritanian upwelling. Bromide and chloride deficits in
coarse mode aerosol at both the CVAO and on D319 and the
continuous abundance of inorganic gaseous halogen species at
CVAO indicate significant reactive cycling of halogens.
Aircraft measurements of O3 and CO show that
surface measurements are representative of the entire boundary
layer in the vicinity both in diurnal variability and absolute
levels. Above the inversion layer similar diurnal behaviour
in O3 and CO is observed at lower mixing ratios
in the air that had originated from south of Cape Verde,
possibly from within the ITCZ. ECMWF calculations on two days
indicate very different boundary layer depths and aircraft
flights over the ship replicate this, giving confidence in the
calculated boundary layer depth. |
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