The evolving role of weather types on rainfall chemistry under large reductions in pollutant emissions

Tso, Chak-Hau Michael; Monteith, Don ORCID:; Scott, Tony; Watson, Helen; Dodd, Beverley; Pereira, M. Gloria ORCID:; Henrys, Peter; Hollaway, Michael; Rennie, Susannah; Lowther, Aaron; Watkins, John ORCID:; Killick, Rebecca; Blair, Gordon ORCID: 2022 The evolving role of weather types on rainfall chemistry under large reductions in pollutant emissions. Environmental Pollution, 299, 118905. 11, pp.

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Long-term change and shorter-term variability in the atmospheric deposition of pollutants and marine salts can have major effects on the biogeochemistry and ecology of soils and surface water ecosystems. In the 1980s, at the time of peak acid deposition in the UK, deposition loads were highly dependent on prevailing weather types, and it was postulated that future pollution recovery trajectories would be partly dependent on any climate change-driven shifts in weather systems. Following three decades of substantial acidic emission reductions, we used monitoring data collected between 1992 and 2015 from four UK Environmental Change Network (ECN) sites in contrasting parts of Great Britain to examine the trends in precipitation chemistry in relation to prevailing weather conditions. Weather systems were classified on the basis of Lamb weather type (LWT) groupings, while emissions inventories and clustering of air mass trajectories were used to interpret the observed patterns. Concentrations of ions showed clear differences between cyclonic-westerly-dominated periods and others, reflecting higher marine and lower anthropogenic contributions in Atlantic air masses. Westerlies were associated with higher rainfall, higher sea salt concentrations, and lower pollutant concentrations at all sites, while air mass paths exerted additional controls. Westerlies therefore have continued to favour higher sea salt fluxes, whereas emission reductions are increasingly leading to positive correlations between westerlies and pollutant fluxes. Our results also suggest a shift from the influence of anthropogenic emissions to natural emissions (e.g., sea salt) and climate forcing as they are transported under relatively cleaner conditions to the UK. Westerlies have been relatively frequent over the ECN monitoring period, but longer-term cyclicity in these weather types suggests that current contributions to precipitation may not be sustained over coming years.

Item Type: Publication - Article
Digital Object Identifier (DOI):
UKCEH and CEH Sections/Science Areas: Pollution (Science Area 2017-)
Soils and Land Use (Science Area 2017-)
Water Resources (Science Area 2017-)
ISSN: 0269-7491
Additional Information. Not used in RCUK Gateway to Research.: Open Access paper - full text available via Official URL link.
Additional Keywords: rainfall chemistry, deposition, major ions, Lamb weather types, climatic effects
NORA Subject Terms: Ecology and Environment
Date made live: 11 Mar 2022 16:42 +0 (UTC)

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