Aerosol decadal trends - Part 2: In-situ aerosol particle number concentrations at GAW and ACTRIS stations

Research output: Contribution to journalArticle


We have analysed the trends of total aerosol particle number concentrations (N) measured at long-term measurement stations involved either in the Global Atmosphere Watch (GAW) and/or EU infrastructure project ACTRIS. The sites are located in Europe, North America, Antarctica, and on Pacific Ocean islands. The majority of the sites showed clear decreasing trends both in the full-length time series, and in the intra-site comparison period of 2001-2010, especially during the winter months. Several potential driving processes for the observed trends were studied, and even though there are some similarities between N trends and air temperature changes, the most likely cause of many northern hemisphere trends was found to be decreases in the anthropogenic emissions of primary particles, SO2 or some co-emitted species. We could not find a consistent agreement between the trends of N and particle optical properties in the few stations with long time series of all of these properties. The trends of N and the proxies for cloud condensation nuclei (CCN) were generally consistent in the few European stations where the measurements were available. This work provides a useful comparison analysis for modelling studies of trends in aerosol number concentrations.


  • A. Asmi
  • M. Collaud Coen
  • J. A. Ogren
  • E. Andrews
  • P. Sheridan
  • A. Jefferson
  • E. Weingartner
  • U. Baltensperger
  • N. Bukowiecki
  • H. Lihavainen
  • N. Kivekas
  • E. Asmi
  • P. P. Aalto
  • M. Kulmala
  • A. Wiedensohler
  • W. Birmili
  • A. Hamed
  • C. O'Dowd
  • S. G. Jennings
  • R. Weller
  • H. Flentje
  • A. M. Fjaeraa
  • M. Fiebig
  • C. L. Myhre
  • A. G. Hallar
  • P. Laj
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Subatomic Physics
Original languageEnglish
Pages (from-to)895-916
JournalAtmospheric Chemistry and Physics
Issue number2
Publication statusPublished - 2013
Publication categoryResearch

Bibliographic note

The information about affiliations in this record was updated in December 2015. The record was previously connected to the following departments: Nuclear Physics (Faculty of Technology) (011013007)