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Geosciences LibreTexts

17.12: Review

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  • The probability of any wind speed at a particular location can be described by a Weibull distribution. The distribution of wind directions can be plotted on a wind rose. Regions with greater probability of moderate winds are ideal for siting wind turbines.

    During weak synoptic forcing (weak geostrophic winds), local circulations can be driven by thermal forcings. Examples include anabatic (warm upslope) and katabatic (cold downslope) winds, mountain and valley winds, and sea breezes near coastlines.

    During strong synoptic forcing, winds can be channeled through gaps, can form downslope windstorms, and can create mountain waves and wave drag. The winds in short gaps can be well described by open-channel hydraulics and Bernoulli’s equation. Winds in longer gaps and fjords are influenced by Coriolis force.

    The Bora is a cold downslope wind driven dynamically by the synoptic-scale flow. Foehn winds are also driven dynamically, but are warm, and can be enhanced by orographic precipitation and latent heating. Hydraulic jumps occur downstream of bora winds and in some gap flows as the flow re-adjusts to hydrostatic equilibrium.

    Wind and temperature instruments are constructed to minimize dynamic pressure and heating errors. Wind speed is reduced inside plant and urban canopies. The urban-heat-island effect of cities can induce local circulations.