Orographic enhancement of wet deposition in the United Kingdom: Continuous monitoring

D. Fowler, I. D. Leith, J. Binnie, A. Crossley, D. W F Inglis, T. W. Choularton, M. Gay, J. W S Longhurst, D. E. Conland

    Research output: Contribution to journalArticlepeer-review


    Continuous monitoring of cloud and rain samples at three mountain sites in the UK has allowed consideration of the long term impact of the enhancement of the wet deposition of pollutants by orographic effects, specifically the scavenging of cap cloud droplets by rain falling from above (the seeder-feeder effects). The concentration of the major pollutant ions in the cloud water is related to the relative proximity of each site to marine and anthropogenic sources of aerosol. In general, the concentrations of major ions in precipitation at summit sites exceed those in precipitation to low ground nearby by 20% to 50%. Concentrations in orographic cloud exceed those in upwind rain by between a factor of five and ten. The results are consistent with seeder-feeder scavenging of hill cloud by falling precipitation in which the average concentration of ions in scavenged hill cloud exceed those in precipitation upwind by a factor of 1.7 to 2.3 for sulphate and nitrate respectively at Dunslair Heights and 1.5 to 1.8 for sulphate and nitrate at Holme Moss. The results suggest that the parameterisation of this relationship with scavenged feeder cloud water concentrations assumed to exceed those in seeder rain by a factor of two for the production of predictive maps of wet deposition in mountainous regions of the U.K. is satisfactory.
    Original languageEnglish
    Pages (from-to)2107-2112
    Number of pages5
    JournalWater, Air, and Soil Pollution
    Issue number4
    Publication statusPublished - 4 Dec 1995


    • orographic enhancement
    • seeder-feeder
    • wet deposition


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