The Pennines experiment 2004
Gaudex 2003
This project involved a group carrying out an airflow experiment over a ridge called Gaudergrat near Davos in Switzerland. Gaudergrat is located on the alpine plateau at about 2200 m altitude and the ridge itself is about 250 m high and triangular in cross-section. Air passing over the ridge separates from the surface at the crest, giving rise to a closed eddy or rotor in the lee. The experiment studied this rotor and its formation mechanisms.
Measurements of the flow through a mountain pass
In collaboration with the University of Innsbruck, measurements of the flow through the Brenner Pass were made during the field phase of the Mesoscale Alpine Programme. Automatic weather stations (including microbarographs) and ultrasonic anemometers were deployed along the Wipptal Valley floor and on the valley sides as part of the GAP field project, aimed at examining the near-surface momentum budget, vertical structure of the flow and the occurrence of hydraulic jumps during foehn events in the Alpine region.
Laboratory simulations of flows over hills
Laboratory measurements of flows over idealised model hills are being conducted at the Environmental Flow Research Centre (EnFlo), University of Surrey. The experiments made use of the EnFlo stratified wind tunnel facility and were aimed at studying the response of the turbulent boundary-layer to hills of varying slopes for a range of stratification. Of particular interest were the occurrence of lee flow separation and how internal gravity waves generated by the model hills were affected by turbulent boundary-layer processes.
Numerical modelling of flows over mountains
A range of numerical models were being used to attack problems such as the interaction of the turbulent boundary-layer flow with the gravity wave response in the free troposphere, convective boundary layer flows over hills and very strongly stratified flows past mountains. The group developed a variety of in-house numerical models for studying orographic flows. These ranged in complexity from a massively-parallel adaptive mesh numerical model to a simple linear three-dimensional model suitable for gravity-wave forecasting.
A linear three-dimensional numerical model (3dVOM) was recently used to forecast gravity wave motions over Wales for the Aberystwyth Egrett Experiment.
A similar model, incorporating representation of boundary-layer processes, was used to provide forecasts for lee waves and rotor formation at Mount Pleasant Airfield on the Falkland Islands.
A programme of field experiments
These experiments (starting in 1991) have been run in collaboration with the UK Forestry Commission, the Met. Office, UMIST, the British Antarctic Survey and the University of Reading. The experiments are aimed at studying the flow over hills with heights similar to the boundary-layer depth and widths of a few kilometres. Details of a recent field campaign (ISLE) conducted by the group on the Isle of Arran.