The scientific objectives of this programme are to elucidate the processes and environmental conditions under which homogeneous nucleation of new aerosol particles is promoted in the coastal atmosphere. In particular, the objectives are as following:
(l) Determine the conditions and the rates under which homogeneous heteromolecular nucleation occurs in the coastal boundary layer (i.e. pre-existing aerosol surface area; precursor gas concentration; micro- and macro-scale meteorology).
(2) Examine whether these nucleation events can be explained by binary or ternary heteromolecular nucleation of the following schemes: H2SO4-H20 or NH3-H2so4-H2o or NH3-H2øMSA/HCl/HNO3, or whether alternative nucleation schemes are likely to explain the observed events i.e. organic embryo formation followed by organic and/or sulphate growth.
(3) Examine the influence of anthropogenic/continental air parcel mixing on coastal nucleation.
(4) Explore the lifetime of these new particles and their survival yield.
(5) Examine the long-term frequency of occurrence of coastal nucleation bursts and their duration.
In order to achieve the above objectives, fast response measurements of nucleation rates, the complete aerosol size distribution (and thus, surface area), aerosol precursors and meteorological parameters, using state-of-art instruments and techniques will be conducted. In parallel to the experimental work, new nucleation theories will be applied to numerical models in order to study nucleation processes such as ternary homogeneous heterogeneous nucleation. The combined measurements and modelling studies will serve to put nucleation processes into a more robust theoretical framework.
These studies will be conducted at a clean coastal site on the western edge of Europe where homogeneous nucleation is regularly observed in both clean and anthropogenicallyinfluenced conditions. Thus, this site provides the best and most cost effective option available for the study of coastal homogeneous nucleation processes. Long term measurements of nucleation events will be conducted to examine the temporal frequency of occurrence and any seasonal variation.
Elucidation of these nucleation processes is required, not only by the scientific community in general, but also by climate modellers in order to reduce the uncertainty in the prediction of climate change by atmospheric aerosol.
KEYWORDS: homogeneous nucleation, aerosol, coastal, precursor
Funding SchemeCSC - Cost-sharing contracts
LE1 9BH Leicester
2509 JG Den Haag ('S-gravenhage)
106 91 Stockholm
LA1 4YQ Lancaster /High Bantham
B15 2TT Birmingham