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Scientific question: Multi-scale flow interactions in complex terrain

Hypotheses: Local circulation in the valley represents complex interactions between thermal circulation, regional flow and synoptic forcing. Thus, local flow is highly variable in space and time, depending on the strengths of each contributor and interactions thereof. Turbulence and mixing in the valley (and hence eddy-coefficients) are also highly variable over a range of scales.

Approach:

  1. Characterize synoptic, regional and mesoscales, including forcing such as pressure gradients and sea surface temperature (site is ~ 100 km from the coast);

  2. Measure local conditions and their evolution at selected sites (i.e. flow collision, interaction and flow distortion hotspots, identified intuitively or long-term monitoring) at high space-time resolution, including turbulence and fluxes;

  3. Identify processes and phenomena – shear instabilities, internal waves, slope flows, flow collisions – at locations in (b) via scanning Lidars, IR imaging, remote and in-situ sensing, and relate their appearance to local conditions (e.g. dimensionless parameters);

  4. Delineate physical mechanisms and interactions thereof, identify their space-time variability and parameterize relevant property fluxes;

  5. Demarcate appearance of various flow regimes as functions of (suitably scaled) property footprints.

Implications: Strong interactions of synoptic and thermally/mechanically induced flows occur at micro- or smaller scales (Sturman et al. 2003; Fernando et al. 2015), but their flux footprints are unknown. Careful multi-scale observations are invaluable for improving microscale models (Landberg et al. 2003; Liu et al. 2011).