Flow and Plume Dispersion in a Coastal Valley

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  • 1 CSIRO Division of Atmospheric Research, Aspendale, Victoria, Australia
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Abstract

An analysis is carried out of summertime surface and upper-air wind and temperature data from the Latrobe Valley in southeastern Australia. An easterly sea breeze is found to regularly penetrate over 100 km up the east-west-oriented valley, meeting a sea breeze from the south coat in late afternoon. The latter enters the valley over a saddle in the Strzelecki Ranges to the south. Over a 5-day period of steady synoptic flow, winds below 1500 m fluctuated between easterly and westerly with a diurnal period, while above this height up to 3000 m, the wind direction remained westerly. The westerly winds were particularly surprising, as the synoptic pressure charts showed a northeasterly pressure gradient over the period.

Power stations are located in the Latrobe Valley well inland from the coast, and findings from the wind-field analysis are used to examine the dispersion of plumes from these sources. It is concluded that the sea breezes replace polluted mixed-layer air with clean air as they penetrate up the valley, and that plume material is advected out of each end of the valley at upper levels overnight.

Abstract

An analysis is carried out of summertime surface and upper-air wind and temperature data from the Latrobe Valley in southeastern Australia. An easterly sea breeze is found to regularly penetrate over 100 km up the east-west-oriented valley, meeting a sea breeze from the south coat in late afternoon. The latter enters the valley over a saddle in the Strzelecki Ranges to the south. Over a 5-day period of steady synoptic flow, winds below 1500 m fluctuated between easterly and westerly with a diurnal period, while above this height up to 3000 m, the wind direction remained westerly. The westerly winds were particularly surprising, as the synoptic pressure charts showed a northeasterly pressure gradient over the period.

Power stations are located in the Latrobe Valley well inland from the coast, and findings from the wind-field analysis are used to examine the dispersion of plumes from these sources. It is concluded that the sea breezes replace polluted mixed-layer air with clean air as they penetrate up the valley, and that plume material is advected out of each end of the valley at upper levels overnight.

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