Federation and Meteorology, Australian Meteorology through the 20th Century, page 1607

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Federation and Meteorology

Australian Meteorology through the 20th Century

Introduction

The Origins of Australian Meteorology

Meteorology in the 20th Century

The Weather and Climate of the Twentieth Century
Rainfall
Temperature
Tropical Cyclones
Floods
Droughts
Bushfires
Severe Storms

The Great Weather and Climate Events of the Twentieth Century

A Century of Progress in Science and Service

References

Australian Meteorological Milestones of the 20th Century

Endnotes

Index
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The Weather and Climate of the Twentieth Century

The twentieth century began with Australia still in the grip of the Federation Drought. It witnessed several extended periods of drought and flood associated with the irregular fluctuations of the Southern Oscillation (Figure 6), many dramatic individual weather events in all States and a gradual overall warming trend across the continent. The general features of the twentieth century climate have been described in various publications (Bureau of Meteorology 1989; Zillman 1994; Bureau of Meteorology 2000). Some of the more notable individual events and trends in Australian weather and climate over the century are described in the following pages.

Figure 6 Annual values of the Southern Oscillation Index (SOI), a measure of fluctuations in the surface pressure difference between Tahiti and Darwin and a useful indicator of the broadscale controls on Australian weather.

Rainfall

The average annual rainfall over Australia from 1900 to 1999 is shown in Figure 7 along with an eleven-year running mean. The very dry period following Federation and the above average rainfall in the 50s and 70s are clearly evident. Overall, there is a very weak rising trend in total rainfall during the century, although individual districts have experienced much stronger trends, both positive and negative, as shown in Figure 8.

Figure 7 Averaged annual mean rainfall (mm) over Australia, 1900–. The solid line shows the eleven-yaer running mean.

Figure 8 The spatial pattern of trends in annual mean rainfall over Australia 1900–99 in mm per century. Green areas have become wetter and brown areas drier.

The maps comprising Figure 9 show the distribution of annual rainfall over the continent in terms of the three terciles—above average, near average and below average—for each year from 1900 to 1999.

Figure 9 These maps show the distribution of annual rainfall over Australia during the twentieth century. Above normal (third tercile) is shown as blue, near normal (second tercile) as white and below normal (first tercile) as red.

Bureau of Meteorology

© Online Edition Australian Science and Technology Heritage Centre and Bureau of Meteorology 2001
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