Abstract : L.6
Wind patterns observed in the boundary layer of the Owens Valley, Sierra Nevada

Ralph Burton, Stephen Mobbs, Simon Vosper, Peter Sheridan, Ian Brooks, Barbara Brooks
University of Leeds

A unique orographic dataset, obtained during the recent Terrain-induced Rotor Experiment (T-REX) in the Sierra Nevada mountains, U.S.A, has been analysed by principal components analysis (PCA). The latter is an extremely powerful method of determining any underlying patterns in large volumes of (otherwise unmanageable) data. The method has been successfully applied to lee and valley surface wind measurements collected by a network of automatic weather stations operated during T-REX.

Underlying structures (such as up- and downslope winds; cross-valley winds) will be seen to be dominant patterns in the valley: the fact that the PCA detects such patterns is significant, and indicates large-scale coherent (and perhaps predictable) flow.

The dominant wind patterns will be related to the pressure gradient in the valley, the heat fluxes observed on the surface, and the general upper-level flow. In particular, the temporal evolution of the wind structures is determined during periods of severe downslope winds and/or suspected rotor formation.

Additionally, these PCA structures will be related to results from the U.K. Met Office Unified Model, initialised with a realistic orography dataset and suitable initial conditions.