Temperature inversions at Anglesea, Victoria

As an exercise in simple microclimatic techniques, and as an aid in the correct dimensioning of power-station chimnys to be built at Anglesea, a one-year study of temperature and wind conditions was carried out in and above the valley of the Anglesea River. A nocturnal surface inversion was observed in the valley on about one-half of the nights of the year of observation (44% in summer and autumn, 63% in winter, 52% in spring), the occurrence of an inversion being dependent on the absence of wind in the valley. Consequently the inversions varied widely in duration and in intensity. Thermograph and anemograph records made at the proposed power-station site in the valley, and thermograph records for points on the surrounding hills, comprised the basic data collected during the study. These were supple mented by regular pilot balloon wind soundings and occasional tethered-balloon temperature soundings, made during a three-month period in summer and a three-week period in early winter. Combined with the available radiosonde and pilot-balloon data from Laverton (50 miles to the north-east) these observations made it possible to construct an outline of the low-level nocturnal atmospheric structure over the Anglesea valley on inversion occasions, and to draw up a tentative frequency table of inversion heights showing the effects of the upper wind speed and direction, and of the stability of the layer immediately above the surface inversion.