Observation and modelling of variability in flow over complex terrain

Barkwith, AKAP 2009, Observation and modelling of variability in flow over complex terrain , PhD thesis, Salford : University of Salford.

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This thesis examines the way in which remote sensing instrumentation can be used to advance our understanding of the interactions between complex terrain and the atmospheric boundary layer (ABL). When mean flow speed is of moderate strength and the ABL is stable, mechanical effects will dominate thermal effects in modifying flow speed and direction. Boundary layer measurements were made using the scanning Salford 10 micron pulsed CO2 Doppler lidar during the 2005 Convective Storm Initiation Project (CSIP), above the heterogeneous orography that surrounds Faccombe, Hampshire, UK. A new method of detecting boundary layer flow perturbations was developed, and successfully applied to the lidar data, giving a clearer insight into flow modification that occurs above complex terrain. The observations are compared to the output from a simple one dimensional boundary layer flow prediction numerical model, and the three dimensional Computational Fluid Dynamics model (CFD), WRF (Weather Research and Forecasting). Reasonable correlation was found between the lidar data and the simple model output; however, the model results are spatially limited and have many associated assumptions, which are discussed. The WRF model was found to be adequate at predicting flow differences at lower altitudes, outputting well defined structures consisting of perturbed flow. However, this model tended to under predict the details of flow difference at higher altitudes in comparison to the CSIP lidar observations. The inability of WRF and similar CFD models to predict the detailed effects of orographically induced variation on upper level ABL flow is of concern, as the inaccuracies affect the performance of such models in reproducing flows on scales of importance in forecasting local weather and pollutant dispersion.

Item Type: Thesis (PhD)
Contributors: Collier, CG (Supervisor)
Schools: Schools > School of Environment and Life Sciences > Ecosystems and Environment Research Centre
Schools > School of Environment and Life Sciences
Depositing User: Institutional Repository
Date Deposited: 03 Oct 2012 13:34
Last Modified: 04 Aug 2022 11:27
URI: https://usir.salford.ac.uk/id/eprint/26563

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