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Urban NO2 and NO pollution in relation to the North Atlantic Oscillation NAO

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Author

  • Maria Grundström
  • Hans Linderholm
  • Jenny Klingberg
  • Håkan Pleijel

Summary, in English

The North Atlantic Oscillation (NAO), a measure of the strength of the zonal wind across the North Atlantic Ocean, strongly influences weather conditions in NW Europe, e.g. temperature, precipitation and wind, especially during winter. It was hypothesised that elevated concentrations of nitrogen oxides in Gothenburg would be enhanced during negative NAO index (NAOI) conditions, representing more anticyclonic weather situations and thus leading to limited air mixing in the urban atmosphere, than situations with NAOI> 0. Hourly wintertime (December-February) concentrations (1997-2006) of NO2, NO, air pressure, temperature and wind direction from an urban rooftop (30 m above street level) in the centre of the City of Gothenburg were analysed in relation to NAOI. Air pressure, the average concentration of nitrogen oxides (NOx = NO2 + NO), as well as the fraction of hourly NO2 and NO concentrations exceeding 90 mu g m(-3) and the fraction of daily NO concentrations exceeding 60 mu g m(-3), were significantly and negatively related to NAOI. Air temperature was positively correlated with NAOI. Southerly and westerly winds were more common in months with positive NAOI, while easterly and northerly winds were overrepresented in months with negative NAOI. High pollution concentrations dominantly occurred in situations with northerly and easterly wind directions. High NO2 and NO concentrations were associated with negative NAOI, especially in the morning when the traffic rush coincided with restricted air mixing. Over the ten-year period there were trends for more negative NAOI and increased time fractions with hourly NO2 concentrations exceeding 90 mu g m(-3). The conclusion of this study is that a climate shift towards higher or lower NAOI has the potential to significantly influence urban air pollution in North-West Europe, and thus the possibility to reach air quality standards, even if emissions remain constant. (C) 2010 Elsevier Ltd. All rights reserved.

Publishing year

2011

Language

English

Pages

883-888

Publication/Series

Atmospheric Environment

Volume

45

Issue

4

Document type

Journal article

Publisher

Elsevier

Topic

  • Meteorology and Atmospheric Sciences

Keywords

  • North Atlantic Oscillation
  • NO2
  • NOx
  • Urban pollution
  • Climate
  • Gothenburg

Status

Published

ISBN/ISSN/Other

  • ISSN: 1352-2310