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UBC Theses and Dissertations

The development and application of a one-level mesoscale atmospheric model over the Lower Fraser Valley of British Columbia Ayotte, Keith Willard


This study involves the use of a one-level mesoscale numerical model to simulate thermally driven, topographically chanelled atmospheric flow over the Lower Fraser Valley of British Columbia. The model used is a modified version of a model developed by Mass Dempsey at the University of Washington. The model was modified to include friction parameterization that was spatially variable and stability dependent. The diabatic surface heating parameterization was also modified to account for spatial variability of surface thermal characteristics. Model runs of July 20,1985 and August 23,1985 are presented in this study. The model is validated using data from a measurement network over the model domain. Statistics of the validation on the two days modeled are presented. It was found that the modified model is quite sensitive to the surface thermal characteristics specified but relatively insensitive to spatial variability of surface roughness. The model is limited in its ability to resolve effects of small topographic features in high Froude number situations but the large scale flow around topographic features is well modeled. Synoptic scale thermally induced pressure gradients are found to affect ability of the model to simulate near surface flow within the domain. It is suggested that the model be nested in a lower resolution grid in order to account for this forcing. It was concluded that this modification, coupled with more accurate specification of the surface characteristics over the model domain would enhance the agreement between modeled and observed fields.

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