Journal of Atmospheric Chemistry

, Volume 67, Issue 2–3, pp 87–140

Seasonal characteristics of tropical marine boundary layer air measured at the Cape Verde Atmospheric Observatory

  • L. J. Carpenter
  • Z. L. Fleming
  • K. A. Read
  • J. D. Lee
  • S. J. Moller
  • J. R. Hopkins
  • R. M. Purvis
  • A. C. Lewis
  • K. Müller
  • B. Heinold
  • H. Herrmann
  • K. Wadinga Fomba
  • D. van Pinxteren
  • C. Müller
  • I. Tegen
  • A. Wiedensohler
  • T. Müller
  • N. Niedermeier
  • E. P. Achterberg
  • M. D. Patey
  • E. A. Kozlova
  • M. Heimann
  • D. E. Heard
  • J. M. C. Plane
  • A. Mahajan
  • H. Oetjen
  • T. Ingham
  • D. Stone
  • L. K. Whalley
  • M. J. Evans
  • M. J. Pilling
  • R. J. Leigh
  • P. S. Monks
  • A. Karunaharan
  • S. Vaughan
  • S. R. Arnold
  • J. Tschritter
  • D. Pöhler
  • U. Frieß
  • R. Holla
  • L. M. Mendes
  • H. Lopez
  • B. Faria
  • A. J. Manning
  • D. W. R. Wallace
Article

DOI: 10.1007/s10874-011-9206-1

Cite this article as:
Carpenter, L.J., Fleming, Z.L., Read, K.A. et al. J Atmos Chem (2010) 67: 87. doi:10.1007/s10874-011-9206-1

Abstract

Observations of the tropical atmosphere are fundamental to the understanding of global changes in air quality, atmospheric oxidation capacity and climate, yet the tropics are under-populated with long-term measurements. The first three years (October 2006–September 2009) of meteorological, trace gas and particulate data from the global WMO/Global Atmospheric Watch (GAW) Cape Verde Atmospheric Observatory Humberto Duarte Fonseca (CVAO; 16° 51′ N, 24° 52′ W) are presented, along with a characterisation of the origin and pathways of air masses arriving at the station using the NAME dispersion model and simulations of dust deposition using the COSMO-MUSCAT dust model. The observations show a strong influence from Saharan dust in winter with a maximum in super-micron aerosol and particulate iron and aluminium. The dust model results match the magnitude and daily variations of dust events, but in the region of the CVAO underestimate the measured aerosol optical thickness (AOT) because of contributions from other aerosol. The NAME model also captured the dust events, giving confidence in its ability to correctly identify air mass origins and pathways in this region. Dissolution experiments on collected dust samples showed a strong correlation between soluble Fe and Al and measured solubilities were lower at high atmospheric dust concentrations. Fine mode aerosol at the CVAO contains a significant fraction of non-sea salt components including dicarboxylic acids, methanesulfonic acid and aliphatic amines, all believed to be of oceanic origin. A marine influence is also apparent in the year-round presence of iodine and bromine monoxide (IO and BrO), with IO suggested to be confined mainly to the surface few hundred metres but BrO well mixed in the boundary layer. Enhanced CO2 and CH4 and depleted oxygen concentrations are markers for air-sea exchange over the nearby northwest African coastal upwelling area. Long-range transport results in generally higher levels of O3 and anthropogenic non-methane hydrocarbons (NMHC) in air originating from North America. Ozone/CO ratios were highest (up to 0.42) in relatively fresh European air masses. In air heavily influenced by Saharan dust the O3/CO ratio was as low as 0.13, possibly indicating O3 uptake to dust. Nitrogen oxides (NOx and NOy) show generally higher concentrations in winter when air mass origins are predominantly from Africa. High photochemical activity at the site is shown by maximum spring/summer concentrations of OH and HO2 of 9 × 106 molecule cm−3 and 6 × 108 molecule cm−3, respectively. After the primary photolysis source, the most important controls on the HOx budget in this region are IO and BrO chemistry, the abundance of HCHO, and uptake of HOx to aerosol.

Keywords

Cape Verde Trace gas Saharan dust Halogen chemistry Dispersion model Atlantic Ocean Air-sea exchange 

Copyright information

© Springer Science+Business Media B.V. 2011

Authors and Affiliations

  • L. J. Carpenter
    • 1
  • Z. L. Fleming
    • 2
  • K. A. Read
    • 1
  • J. D. Lee
    • 1
  • S. J. Moller
    • 1
  • J. R. Hopkins
    • 1
  • R. M. Purvis
    • 1
  • A. C. Lewis
    • 1
  • K. Müller
    • 4
  • B. Heinold
    • 4
  • H. Herrmann
    • 4
  • K. Wadinga Fomba
    • 4
  • D. van Pinxteren
    • 4
  • C. Müller
    • 4
  • I. Tegen
    • 4
  • A. Wiedensohler
    • 4
  • T. Müller
    • 4
  • N. Niedermeier
    • 4
  • E. P. Achterberg
    • 5
  • M. D. Patey
    • 5
  • E. A. Kozlova
    • 6
    • 15
  • M. Heimann
    • 6
  • D. E. Heard
    • 7
  • J. M. C. Plane
    • 7
  • A. Mahajan
    • 7
    • 16
  • H. Oetjen
    • 7
    • 17
  • T. Ingham
    • 8
  • D. Stone
    • 7
    • 9
  • L. K. Whalley
    • 8
  • M. J. Evans
    • 9
    • 18
  • M. J. Pilling
    • 7
  • R. J. Leigh
    • 10
  • P. S. Monks
    • 3
  • A. Karunaharan
    • 3
  • S. Vaughan
    • 7
  • S. R. Arnold
    • 9
  • J. Tschritter
    • 11
  • D. Pöhler
    • 11
  • U. Frieß
    • 11
  • R. Holla
    • 11
  • L. M. Mendes
    • 12
  • H. Lopez
    • 12
  • B. Faria
    • 12
  • A. J. Manning
    • 13
  • D. W. R. Wallace
    • 14
  1. 1.National Centre for Atmospheric Science, Department of ChemistryUniversity of YorkYorkUK
  2. 2.National Centre for Atmospheric Science, Department of ChemistryUniversity of LeicesterLeicesterUK
  3. 3.Department of ChemistryUniversity of LeicesterLeicesterUK
  4. 4.Leibniz-Institut für Troposphärenforschung e.V.LeipzigGermany
  5. 5.School of Ocean and Earth Science, National Oceanography Centre SouthamptonUniversity of SouthamptonSouthamptonUK
  6. 6.Max-Planck-Institut für BiogeochemieJenaGermany
  7. 7.School of ChemistryUniversity of LeedsLeedsUK
  8. 8.National Centre for Atmospheric Science, School of ChemistryUniversity of LeedsLeedsUK
  9. 9.Institute for Climate & Atmospheric Science, School of Earth & EnvironmentUniversity of LeedsLeedsUK
  10. 10.Earth Observation Science, Department of Physics & AstronomyUniversity of LeicesterLeicesterUK
  11. 11.Institute of Environmental PhysicsUniversity of HeidelbergHeidelbergGermany
  12. 12.Instituto Nacional de Meteorologia e Geofísica (INMG)MindeloCape Verde
  13. 13.The Met OfficeExeterUK
  14. 14.Leibniz-Institut für Meereswissenschaften (IFM-GEOMAR) Marine BiogeochemieKielGermany
  15. 15.School of Environmental SciencesUniversity of East Anglia (UEA)NorwichUK
  16. 16.Laboratorio de Ciencias de la Atmósfera y el Clima (CIAC)ToledoSpain
  17. 17.Department of ChemistryUniversity of ColoradoBoulderUSA
  18. 18.Department of ChemistryUniversity of YorkYorkUK

Personalised recommendations