Rainfall variations in Australia during the 20^th century

A study of the average annual rainfall in Australia between 1913 and 1970 (1) shows that there was an abrupt increase in 1945-6, made evident by a cumulative deviation graph of annual values, like Fig.10.10 in the book. (Incidentally, the global mean temperature rise temporarily halted around 1945.)

Daily rainfall data from 125 stations in Australia during 1910-1990 show that the increased rainfall between 1914-45 and ‘46-74 was due to fewer dry days (especially in summer) and more heavy rainfall (2,3). The rainfall in 1946-74 at places in New South Wales and Victoria (i.e. southeastern Australia) was over 10% greater than during the previous 32 years. The largest increases of summer rainfall occurred along the New South Wales coast.

The median daily rainfall amount in Australia between 1910 and 1990 increased by 14%, and the number of dry days fell by 4%. These trends can be seen in an animated loop of annual mean rainfall maps of Australia from 1900 to 1995. There was also a widespread increase of heavy rain in the winter half year, except in the southwest of Western Australia, and inland Queensland.

The annual mean Southern Oscillation Index correlated with annual rainfalls during 1941-70 with a coefficient of over 0.35 in Eastern Australia (1). The correlation coefficient was about zero for places in Western Australia, more remote from the Pacific Ocean.

1. Pittock, A.B. 1975. Climatic change and the pattern of variation of Australian rainfall. Search 6, 498-504.
2. Suppiah, R. & K.J. Hennessy 1997. Trends in the intensity & frequency of heavy rainfall in tropical Australia and links with the Southern Oscillation. Aust. Meteor. Mag. 45, 1-17.
3. Suppiah, R. & K.J. Hennessy 1997. Trends in total rainfall, heavy rain events and dry days in Australia 1910- 1990. Paper to 5th Internat.Conf. on Southern Hemisphere Meteorology and Oceanography, Pretoria (Amer. Meteor. Soc. & South African Soc for Atmos. Sciences), 179-80.