Flow and Plume Dispersion in a Coastal Valley

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 coast 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.