Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Journal topic

Journal metrics

Journal metrics

  • IF value: 5.668 IF 5.668
  • IF 5-year value: 6.201 IF 5-year
    6.201
  • CiteScore value: 6.13 CiteScore
    6.13
  • SNIP value: 1.633 SNIP 1.633
  • IPP value: 5.91 IPP 5.91
  • SJR value: 2.938 SJR 2.938
  • Scimago H <br class='hide-on-tablet hide-on-mobile'>index value: 174 Scimago H
    index 174
  • h5-index value: 87 h5-index 87
Volume 10, issue 17
Atmos. Chem. Phys., 10, 8151–8171, 2010
https://doi.org/10.5194/acp-10-8151-2010
© Author(s) 2010. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: European Integrated Project on Aerosol-Cloud-Climate and Air...

Atmos. Chem. Phys., 10, 8151–8171, 2010
https://doi.org/10.5194/acp-10-8151-2010
© Author(s) 2010. This work is distributed under
the Creative Commons Attribution 3.0 License.

  01 Sep 2010

01 Sep 2010

Enhancement of the aerosol direct radiative effect by semi-volatile aerosol components: airborne measurements in North-Western Europe

W. T. Morgan1, J. D. Allan1,2, K. N. Bower1, M. Esselborn3,*, B. Harris4, J. S. Henzing5, E. J. Highwood4, A. Kiendler-Scharr6, G. R. McMeeking1, A. A. Mensah6, M. J. Northway4, S. Osborne7,**, P. I. Williams1,2, R. Krejci8, and H. Coe1 W. T. Morgan et al.
  • 1Centre for Atmospheric Science, University of Manchester, Manchester, UK
  • 2National Centre for Atmospheric Science, University of Manchester, Manchester, UK
  • 3Institut für Physik der Atmosphäre, Deutsches Zentrum für Luft-und Raumfahrt (DLR), Oberpfaffenhofen, Germany
  • 4Department of Meteorology, University of Reading, UK
  • 5TNO, Utrecht, The Netherlands
  • 6Institute for Chemistry and Dynamics of the Geosphere, Institute 2: Troposphere, Research Centre Jülich, Jülich, Germany
  • 7Met Office, Exeter, UK
  • 8Department of Applied Environmental Science, Atmospheric Science Unit, Stockholm University, Sweden
  • *now at: European Southern Observatory (ESO), 85748 Garching bei München, Germany
  • **now at: Met Office, Cardington, UK

Abstract. A case study of atmospheric aerosol measurements exploring the impact of the vertical distribution of aerosol chemical composition upon the radiative budget in North-Western Europe is presented. Sub-micron aerosol chemical composition was measured by an Aerodyne Aerosol Mass Spectrometer (AMS) on both an airborne platform and a ground-based site at Cabauw in the Netherlands. The examined period in May 2008 was characterised by enhanced pollution loadings in North-Western Europe and was dominated by ammonium nitrate and Organic Matter (OM). Both ammonium nitrate and OM were observed to increase with altitude in the atmospheric boundary layer. This is primarily attributed to partitioning of semi-volatile gas phase species to the particle phase at reduced temperature and enhanced relative humidity. Increased ammonium nitrate concentrations in particular were found to strongly increase the ambient scattering potential of the aerosol burden, which was a consequence of the large amount of associated water as well as the enhanced mass. During particularly polluted conditions, increases in aerosol optical depth of 50–100% were estimated to occur due to the observed increase in secondary aerosol mass and associated water uptake. Furthermore, the single scattering albedo was also shown to increase with height in the boundary layer. These enhancements combined to increase the negative direct aerosol radiative forcing by close to a factor of two at the median percentile level. Such increases have major ramifications for regional climate predictions as semi-volatile components are often not included in aerosol models.

The results presented here provide an ideal opportunity to test regional and global representations of both the aerosol vertical distribution and subsequent impacts in North-Western Europe. North-Western Europe can be viewed as an analogue for the possible future air quality over other polluted regions of the Northern Hemisphere, where substantial reductions in sulphur dioxide emissions have yet to occur. Anticipated reductions in sulphur dioxide in polluted regions will result in an increase in the availability of ammonia to form ammonium nitrate as opposed to ammonium sulphate. This will be most important where intensive agricultural practises occur. Our observations over North-Western Europe, a region where sulphur dioxide emissions have already been reduced, indicate that failure to include the semi-volatile behaviour of ammonium nitrate will result in significant errors in predicted aerosol direct radiative forcing. Such errors will be particularly significant on regional scales.

Publications Copernicus
Download
Citation