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The Great Dun Fell experiment 1995 : An overview

Bower, K. N. ; Choularton, T. W. ; Gallagher, M. W. ; Colvile, R. N. ; Beswick, K. M. ; Inglis, D. W.F. ; Bradbury, C. ; Martinsson, B. G. LU ; Swietlicki, E. LU and Berg, O. H. , et al. (1999) In Atmospheric Research 50(3-4). p.151-184
Abstract

During March and April of 1995 a major international field project was conducted at the UMIST field station site on Great Dun Fell in Cumbria, Northern England. The hill cap cloud which frequently envelopes this site was used as a natural flow through reactor to examine the sensitivity of the cloud microphysics to the aerosol entering the cloud and also to investigate the effects of the cloud in changing the aerosol size distribution, chemical composition and associated optical properties. To investigate these processes, detailed measurements of the cloud water chemistry (including the chemistry of sulphur compounds, organic and inorganic oxidised nitrogen and ammonia), cloud microphysics and properties of the aerosol and trace gas... (More)

During March and April of 1995 a major international field project was conducted at the UMIST field station site on Great Dun Fell in Cumbria, Northern England. The hill cap cloud which frequently envelopes this site was used as a natural flow through reactor to examine the sensitivity of the cloud microphysics to the aerosol entering the cloud and also to investigate the effects of the cloud in changing the aerosol size distribution, chemical composition and associated optical properties. To investigate these processes, detailed measurements of the cloud water chemistry (including the chemistry of sulphur compounds, organic and inorganic oxidised nitrogen and ammonia), cloud microphysics and properties of the aerosol and trace gas concentrations upwind and downwind of the cap cloud were undertaken. It was found that the cloud droplet number was generally strongly correlated to aerosol number concentration, with up to 2000 activated droplets cm-3 being observed in the most polluted conditions. In such conditions it was inferred that hygroscopic organic compounds were important in the activation process. Often, the size distribution of the aerosol was substantially modified by the cloud processing, largely due to the aqueous phase oxidation of S(IV) to sulphate by hydrogen peroxide, but also through the uptake and fixing of gas phase nitric acid as nitrate, increasing the calculated optical scattering of the aerosol substantially (by up to 24%). New particle formation was also observed in the ultrafine aerosol mode (at about 5 nm) downwind of the cap cloud, particularly in conditions of low total aerosol surface area and in the presence of ammonia and HCl gases. This was seen to occur at night as well as during the day via a mechanism which is not yet understood. The implications of these results for parameterising aerosol growth in Global Climate Models are explored.

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keywords
Aerosol Chemistry, Aerosol hygroscopicity, Aerosol modification, Aerosol size, Airflow, Ammonia, Atmospheric chemistry, Climate, Cloud microphysics, Cloud processing, Cloud water chemistry, Hill cap cloud, Hydrogen peroxide, Modelling, Multiple measuring sites, Nitrate, Nitrogen oxides, Organic species, Ozone, Parameterisation, Sulphate, Sulphur dioxide, Ultrafine particle production
in
Atmospheric Research
volume
50
issue
3-4
pages
34 pages
publisher
Elsevier
external identifiers
  • scopus:0342770292
ISSN
0169-8095
DOI
10.1016/S0169-8095(98)00103-3
language
English
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yes
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10aa29b6-995e-4325-8c85-15be66e5c602
date added to LUP
2019-05-16 09:41:16
date last changed
2019-11-04 12:19:46
@article{10aa29b6-995e-4325-8c85-15be66e5c602,
  abstract     = {<p>During March and April of 1995 a major international field project was conducted at the UMIST field station site on Great Dun Fell in Cumbria, Northern England. The hill cap cloud which frequently envelopes this site was used as a natural flow through reactor to examine the sensitivity of the cloud microphysics to the aerosol entering the cloud and also to investigate the effects of the cloud in changing the aerosol size distribution, chemical composition and associated optical properties. To investigate these processes, detailed measurements of the cloud water chemistry (including the chemistry of sulphur compounds, organic and inorganic oxidised nitrogen and ammonia), cloud microphysics and properties of the aerosol and trace gas concentrations upwind and downwind of the cap cloud were undertaken. It was found that the cloud droplet number was generally strongly correlated to aerosol number concentration, with up to 2000 activated droplets cm<sup>-3</sup> being observed in the most polluted conditions. In such conditions it was inferred that hygroscopic organic compounds were important in the activation process. Often, the size distribution of the aerosol was substantially modified by the cloud processing, largely due to the aqueous phase oxidation of S(IV) to sulphate by hydrogen peroxide, but also through the uptake and fixing of gas phase nitric acid as nitrate, increasing the calculated optical scattering of the aerosol substantially (by up to 24%). New particle formation was also observed in the ultrafine aerosol mode (at about 5 nm) downwind of the cap cloud, particularly in conditions of low total aerosol surface area and in the presence of ammonia and HCl gases. This was seen to occur at night as well as during the day via a mechanism which is not yet understood. The implications of these results for parameterising aerosol growth in Global Climate Models are explored.</p>},
  author       = {Bower, K. N. and Choularton, T. W. and Gallagher, M. W. and Colvile, R. N. and Beswick, K. M. and Inglis, D. W.F. and Bradbury, C. and Martinsson, B. G. and Swietlicki, E. and Berg, O. H. and Cederfelt, S. I. and Frank, G. and Zhou, J. and Cape, J. N. and Sutton, M. A. and McFadyen, G. G. and Milford, C. and Birmili, W. and Yuskiewicz, B. A. and Wiedensohler, A. and Stratmann, F. and Wendisch, M. and Berner, A. and Ctyroky, P. and Galambos, Z. and Mesfin, S. H. and Dusek, U. and Dore, C. J. and Lee, D. S. and Pepler, S. A. and Bizjak, M. and Divjak, B.},
  issn         = {0169-8095},
  language     = {eng},
  month        = {03},
  number       = {3-4},
  pages        = {151--184},
  publisher    = {Elsevier},
  series       = {Atmospheric Research},
  title        = {The Great Dun Fell experiment 1995 : An overview},
  url          = {http://dx.doi.org/10.1016/S0169-8095(98)00103-3},
  doi          = {10.1016/S0169-8095(98)00103-3},
  volume       = {50},
  year         = {1999},
}