Modeling of Summertime Flow and Dispersion in the Coastal Terrain of Southeastern Australia

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Abstract
The Latrobe Valley is situated in a coastal region of complex terrain in southeastern Australia. During typical summertime conditions of light synoptic winds and clear skies, the low-level regional wind field is dominated by sea-breeze and slope-wind circulations. Westerly winds at heights between 1500 and 3000 m are observed to move progressed down to the surface during the night and early morning hours. This unusual feature of the diurnal wind cycle occurs when the synoptic pressure gradient up to 700 hPa is weak, producing a 3–4 m s−1 geostrophic wind from the northeast. A three-dimensional mesoscale model with detailed boundary-layer physics is employed to examine this behavior. Good agreement with observed winds can only be obtained when a negligible synoptic-scale wind is specified. Laboratory experiments and use of a nested model with a larger outer domain show that this occurs because blocking of the northeasterly synoptic flow by upstream orography produces a stagnation region over the m... Abstract The Latrobe Valley is situated in a coastal region of complex terrain in southeastern Australia. During typical summertime conditions of light synoptic winds and clear skies, the low-level regional wind field is dominated by sea-breeze and slope-wind circulations. Westerly winds at heights between 1500 and 3000 m are observed to move progressed down to the surface during the night and early morning hours. This unusual feature of the diurnal wind cycle occurs when the synoptic pressure gradient up to 700 hPa is weak, producing a 3–4 m s−1 geostrophic wind from the northeast. A three-dimensional mesoscale model with detailed boundary-layer physics is employed to examine this behavior. Good agreement with observed winds can only be obtained when a negligible synoptic-scale wind is specified. Laboratory experiments and use of a nested model with a larger outer domain show that this occurs because blocking of the northeasterly synoptic flow by upstream orography produces a stagnation region over the m...

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