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dc.contributor.advisorClark, Douglasen
dc.contributor.advisorEssery, Richarden
dc.contributor.authorBauduin-Ménard, Cécileen
dc.date.accessioned2011-02-02T11:31:14Z
dc.date.available2011-02-02T11:31:14Z
dc.date.issued2010
dc.identifier.urihttp://hdl.handle.net/1842/4756
dc.description.abstractObservational and modelling studies show that the warming of the Arctic is leading to shrub expansion. This shift in vegetation cover is expected to significantly alter the distribution of snow across the landscape and the interactions between the land surface and the atmosphere. Shrubs capture wind-blown snow, increasing snow depth and decreasing winter water loss through sublimation, and bend beneath the weight of snow, affecting albedo. Snow is highly insulative and affects the soil hydrological and thermal properties. Therefore, as the snow-vegetation-soil interactions is expected to be at the core of feedback loops leading to further shrub expansion, there is a need for models to be able to simulate these processes accurately. Initially using the community land surface model JULES (Joint UK Land Environment Simulator) this study investigates the effects of shrub-tundra on snow and runoff. Alternative formulations of soil processes are proposed, which are better adapted to the representation of subgrid heterogeneity in cold regions than the current model formulation, and evaluated over the Abisko and Torne-Kalix river basins. In addition, a high resolution shrub bending model, which calculates the exposed winter shrub fraction, is developed and parameterised for use alongside the snow cover parameterisation in JULES in order to provide a better representation of shrub-specific processes. This revised JULES more than doubles the efficiency coefficient and halfs the negative bias between modelled and observed runoff in the shrub-tundra Abisko basin. However, the current structure of the model is found to be inadequate for use in investigating the effect of shrub-tundra expansion because it calculates a single energy balance for the snow-free and the snow-covered areas. To address this issue, a distributed three-source (snow-shrub-ground) model (D3SM) is developed. D3SM is evaluated against snow and energy ux measurements from a shrub-tundra basin in the Yukon, Canada, and is found to reproduce snowmelt energetics well. The effects of shrub expansion on the energy balance of the basin during snowmelt are then investigated by increasing the vegetation fraction and canopy height of the current shrub distribution, which is found to be positively correlated with topography. D3SM shows that the most significant effects of shrub expansion in the basin are to reduce the spatial variability of snow depth and to increase the sensible heat flux from the surface to the atmosphere.en
dc.contributor.sponsorCLASSIC networken
dc.contributor.sponsorNatural Environment Research Council (NERC)en
dc.contributor.sponsorIP3 networken
dc.language.isoen
dc.publisherThe University of Edinburghen
dc.relation.haspartThe University of Edinburgh. College of Science and Engineeringen
dc.subjectsnowen
dc.subjectshrub-tundraen
dc.subjectArcticen
dc.subjecthydrometeorologyen
dc.subjectenergy-balanceen
dc.titleModelling the effects of shrub-tundra on snow and runoffen
dc.typeThesis or Dissertationen
dc.type.qualificationlevelDoctoralen
dc.type.qualificationnamePhD Doctor of Philosophyen


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