Chemical composition observed over the mid‐Atlantic and the detection of pollution signatures far from source regions

Lewis, Alastair C.; Evans, M. J.; Methven, John; Watson, N.; Lee, James; Hopkins, James R.; Purvis, R. M.; Arnold, S. R.; McQuaid, James B.; Whalley, Lisa K.; Pilling, Michael J.; Heard, Dwayne E.; Monks, Paul S.; Parker, Alison E.; Reeves, Claire E.; Oram, D. E.; Mills, G.; Bandy, Brian; Stewart, David J.; Coe, Hugh; Williams, P. I.; Crosier, Jonathan

doi:10.1029/2006jd007584

Cited by 77 publications

(81 citation statements)

References 36 publications

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“…For air arriving at CVAO in summer, decomposition of PAN can be considered to be effectively complete. Previous measurements of PAN in the mid-Atlantic indicated mixing ratios ranging from more than 3 ppbv above 7 km, to below 5 pptv in the marine boundary layer (Lewis et al, 2007). This study showed that the presence of NO x in the early and later stages of a plume trajectory typically resulted in significant elevation in ozone in the mid Atlantic, albeit with very low in situ NO x detected when measurements were made in the MBL.…”

Section: Greenhouse Gasesmentioning

confidence: 44%

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

et al. 2010

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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 CO 2 and CH 4 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 O 3 and anthropogenic non-methane hydrocarbons (NMHC) in air originating from North America. Ozone/CO ratios were highest (up to 0.42) in European air masses that contain relatively less well-aged air. In air heavily influenced by Saharan dust the O 3 /CO ratio was as low as 0.13, possibly indicating O 3 uptake to dust. Nitrogen oxides (NO x and NO y ) 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 HO 2 of 9 × 10 6 molecule cm -3 and 6 × 10 8 molecule cm -3 , respectively. After the primary photolysis source, the chemistry of IO and BrO, the abundance of HCHO, and aerosol uptake are important for the HO x budget in this region.3

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Section: Greenhouse Gasesmentioning

confidence: 44%

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

et al. 2010

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“…Long-range transport Research over the past two decades has clearly shown that ozone and ozone precursors are regularly exported from their emission source, or point of production, to receptor regions far downwind on the regional, intercontinental and even hemispheric scale (see reviews by Stohl and Eckhardt, 2004;Monks et al, 2009;Council, 2009b;HTAP, 2010). These transport pathways are predominantly from west to east at mid-latitudes, with in situ and satellite-based observations showing that pollution plumes (anthropogenic and biomass burning) not only travel from North America to Europe, or from East Asia to North America, but can also circle the globe (Jacob et al, 1999;Jaffe et al, 1999;Lewis et al, 2007;Wild et al, 2004).…”

Section: Transport and Mixing Processesmentioning

confidence: 99%

Tropospheric ozone and its precursors from the urban to the global scale from air quality to short-lived climate forcer

et al. 2015

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Abstract. Ozone holds a certain fascination in atmospheric science. It is ubiquitous in the atmosphere, central to tropospheric oxidation chemistry, yet harmful to human and ecosystem health as well as being an important greenhouse gas. It is not emitted into the atmosphere but is a byproduct of the very oxidation chemistry it largely initiates. Much effort is focused on the reduction of surface levels of ozone owing to its health and vegetation impacts, but recent efforts to achieve reductions in exposure at a country scale have proved difficult to achieve owing to increases in background ozone at the zonal hemispheric scale. There is also a growing realisation that the role of ozone as a short-lived climate pollutant could be important in integrated air quality climate change mitigation. This review examines current understanding of the processes regulating tropospheric ozone at global to local scales from both measurements and models. It takes the view that knowledge across the scales is important for dealing with air quality and climate change in a synergistic manner. The review shows that there remain a number of clear challenges for ozone such as explaining surface trends, incorporating new chemical understanding, ozone-climate coupling, and a better assessment of impacts. There is a clear and present need to treat ozone across the range of scales, a transboundary issue, but with an emphasis on the hemispheric scales. New observational opportunities are offered both by satellites and small sensors that bridge the scales.

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“…Table 2 details the available isoprene observations for model evaluation fitting these criteria. A small number of aircraft observations are available from the ITOP experiment over the mid North Atlantic Ocean (Lewis et al, 2007), where the aircraft sampled near-surface marine air north-west and south-east of the Azores in July 2004. Limited periods of more frequent measurements are available from ship cruises in the marine surface atmosphere of the Western North Pacific during May 2001 (Matsunaga et al, 2002) and the remote Southern Indian Ocean during December 1997 (Yokouchi et al, 1999).…”

Section: Evaluation Of Marine Isoprene Emissionsmentioning

confidence: 99%

Evaluation of the global oceanic isoprene source and its impacts on marine organic carbon aerosol

et al. 2009

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Abstract. We have combined the first satellite maps of the global distribution of phytoplankton functional type and new measurements of phytoplankton-specific isoprene productivities, with available remote marine isoprene observations and a global model, to evaluate our understanding of the marine isoprene source and its impacts on organic aerosol abundances. Using satellite products to scale up data on phytoplankton-specific isoprene productivity to the global oceans, we infer a mean "bottom-up" oceanic isoprene emission of 0.31±0.08 (1σ )Tg/yr. By minimising the mean bias between the model and isoprene observations in the marine atmosphere remote from the continents, we produce a "topdown" oceanic isoprene source estimate of 1.9 Tg/yr. We suggest our reliance on limited atmospheric isoprene data, difficulties in simulating in-situ isoprene production rates in laboratory phytoplankton cultures, and limited knowledge of isoprene production mechanisms across the broad range of phytoplankton communities in the oceans under different environmental conditions as contributors to this difference between the two estimates. Inclusion of secondary organic aerosol (SOA) production from oceanic isoprene in the model with a 2% yield produces small contributions (0.01-1.4%) to observed organic carbon (OC) aerosol mass at three remote marine sites in the Northern and Southern Hemispheres. Based on these findings we suggest an insignificant role for isoprene in modulating remote marine aerosol abundances, giving further support to a recently postulated primary OC source in the remote marine atmosphere.

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Chemical composition observed over the mid‐Atlantic and the detection of pollution signatures far from source regions

Cited by 77 publications

References 36 publications

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

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

Tropospheric ozone and its precursors from the urban to the global scale from air quality to short-lived climate forcer

Evaluation of the global oceanic isoprene source and its impacts on marine organic carbon aerosol

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