||Federation and Meteorology
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Meteorological Work in Australia
Meteorological Work in Australia: A Review
Map No. 1February 18th, 1890
Map No.2January 14th, 1891
Map No.3March 12th, 1891
Map No. 4, February 5th. 1890, and Map No .5, May 27th, 1893
Map No. 6, June 22nd, 1893
Map No. 7, July 14th, 1893
Map No. 7, July 14th, 1893 (continued)
This map was taken at random from several during a long spell of cyclonic conditions, lasting from the 8th to the 24th, and clearly shows the rapid succession of V-shaped depressions along the south coastlines. With each depression unsettled weather and rain passed along the south coast of the continent. The "low" shown off the Leeuwin when it reached the Bight passed inland over South Australia, causing the rains to be heavier and more general than when the previous depression passed along the south coast further to the south.
Leaving the maps, and speaking generally, I would point out that in both the Northern and Southern Hemispheres is a belt or zone of high pressure, separating the tropical and polar zones of low pressure at the latitude where the return trade and polar winds descend towards the surface of the earth.
The southern belt passes over the extra-tropical or temperate parts of Australia. It is made up of long loops, or anticyclonic areas, being broken up at intervals by low pressure intrusions from the tropics and northerly extensions of V-shaped depressions from the south. When these join they form a barometric trough or valley, effecting a complete rupture of the anticyclonic belt. The position or latitude of this anticyclonic belt depends on the time of the year, and varies in different years. Normally, during the winter the crest of the "high" lies over the interior. approximately about latitude 29° or 30° (vide map 6). North of this the continent is swept by the dry south-east trade winds, whilst to the south we have, in South Australia, a prevalence of dry northerly (north-east to north-west) winds, varied by strong west and southwest winds as coastal depressions pass from west to east, with rain and squally weather. On the east coast west winds prevail during the winter.
The character of our winter season, in South Australia especially, depends very closely on the position of this wall, as it were, of high barometers, which plays a very important part in Australian climate. If it lies too far south, or near the coast, the winter over the southern districts of the colony (I am speaking of South Australia) is dry, but we may, and occasionally do, have under these conditions good rains in the north, due to the extension of tropical depressions bringing rain over the interior of Queensland, New South Wales, and South Australia east of Lake Eyre and the Flinders Range.
On the other hand, if the anticyclonic areas keep more to the north, the southern or coastal V depressions extend further inland, at times being felt as far as the tropics, and we have copious rains all over the colony, as well as in Victoria and western New South Wales. As the depressions pass the winds veer from north-east and north to north-west, west, and south-west. Steady rains set in with the wind at north-east to north, heaviest at north-west, and break up with heavy showers and squalls at south-west, sometimes accompanied by heavy thunderstorms, while the wind is north-west to south-west.
People in Bright Sparcs - Todd, Charles
© Online Edition Australian Science and Technology Heritage Centre and Bureau of Meteorology 2001
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