MAP Objectives
(1)
To elucidate the dominant condensable vapours driving secondary
marine aerosol (SMA) formation.
(2) To quantify the number and size flux of primary inorganic and organic marine
sea-spray aerosol (PMA)
(3) To produce a PMA and iodo-carbon source function using integrated Global
Earth Observing satellite data and in-situ data.
(4) To quantify the impact of SMA and PMA on radiative forcing and atmospheric
chemistry.
MAP will integrate Europe’s leading expertise in aerosol
physics and chemistry and marine biogeochemistry to quantify the production
of primary and secondary marine aerosol formation from natural sources.
The project will build on the current state-of-the-art and recent ground-breaking
results and will focus on the key questions highlighted above.
The field component of MAP will focus on quantifying marine secondary and primary aerosol formation as a function of season and biological activity over the North Atlantic and determine the relative contributions of natural and anthropogenic sources to North Atlantic aerosol. With continuous measurements of aerosol micro-physics, IO and detailed aerosol chemistry, with improved analytical techniques and higher time resolution, the seasonal dependence of SMA and PMA formation on biological activity will be quantified. It should be noted that while there are clearly coastal influence on SMA, a careful analysis on the potential coastal contribution to PMA at Mace Head has illustrated that such sources account <5% to the Aitken and accumulation mode aerosol fields (O’Dowd et al. 2004). To contrast with the cleaner North Atlantic aerosol, parallel measurements of size resolved aerosol chemistry will be made in the more polluted Mediterranean which is subject to a greater variety of aerosol sources. This component will result in an urgent seasonal quantification of aerosol chemical characteristics and formation processes.
The most advanced suite of aerosol and gas analytical technology will be deployed during one ship-borne Intensive Observation Period (IOP) over the North Atlantic during the period of peak plankton activity. In particular, state-of-the-art instruments for measuring aerosol precursors such as iodine oxides, I2, organo-iodine compounds, sulphuric acid, SO2 and organic vapours – all key species involved in secondary new particle formation, will be deployed alongside the most advanced suite of aerosol- and ion/cluster physics measurements. This will provide the most appropriate suite of instrumentation to address key issues associated with new particle formation in the marine boundary layer.
In terms of aerosol chemistry, the best-available-technology and analytical tools for the characterisation and quantification of both the inorganic and organic components of marine aerosol, and their hygroscopic properties will be deployed. Particular attention will focus on the organic component of marine aerosol and the characterisation of its properties. A wide range of techniques ranging from HNMR to mass spectrometry will be used. Innovative techniques, recently evaluated, will be used to identify biological components, and in particular, DNA associated with airborne organic particles. This DNA fingerprinting will provide a direct quantitative link between marine aerosols and specific plankton blooms and life cycles. Micro-meteorological fluxes and fluxes of PMA, surface water speciation of organic matter, sea-air transfer of iodine precursors, and in-situ bubble-mediated aerosol production experiments during the campaign will also represent the state-of-the-art in these areas. It should be noted that while MAP will quantify PMA fluxes and composition up to 10 microns, the main focus will be on the sub-micron component since this dominates the PMA number concentration rather than mass concentration.
The extensive field results will be combined with laboratory results of bubble-mediated sea-air aerosol and gas transfer in the presence of surfactants to develop a more thorough understanding of the key processes relating to primary and secondary aerosol formation. In particular, PMA aerosol production and its chemical speciation and iodine vapour sea-air transfer will be quantified as a function of in-situ characterisation of organic matter at the ocean surface and as a function of satellite derived chlorophyll, wind fields and white cap coverage. This integration of the field, lab, remote-sensing and process model studies will form two GEOSS products which can be integrated into the large scale models to quantify the source of primary aerosol over the ocean and to provide an estimate of the global sea-air transfer of organo-iodine. The resulting modelling tools and integrated GEOSS products will significantly advance our capability of quantifying the impact of marine aerosol on marine boundary layer chemistry, direct and indirect radiative forcing, and impacts on climate and will provide the first assessment of marine aerosol effects with particular attention to iodine-forming aerosols and biogenic bubble-mediated aerosol formation. The large scale models, integrating the most advanced knowledge of marine aerosols into their predictions, will represent the most comprehensive advance in our quantification of the impacts of marine aerosols on atmospheric chemistry and climate.