Storms of Southeast Australia

Alexander et al. (2011) introduce their study by stating the truism that "understanding the long-term variability of storm activity would give a much better perspective on how unusual recent climate variations have been," and they note in this regard that "for southeast and eastern Australia some studies have been able to assess measures of storm activity over longer periods back to the 19th century (e.g., Alexander and Power, 2009; Rakich et al., 2008), finding either a decline in the number of storms or reduction in the strength of zonal geostrophic wind flow," although noting that these studies "were limited to the analysis of only one or two locations."

In an effort designed to significantly expand the database employed in their newest study of the subject, Alexander et al. analyzed storminess across the whole of southeast (SE) Australia using extreme (standardized seasonal 95th and 99th percentiles) geostrophic winds deduced from eight widespread stations possessing sub-daily atmospheric pressure observations dating back to the late 19th century.

The four researchers report that their results "show strong evidence for a significant reduction in intense wind events across SE Australia over the past century." More specifically, they say that "in nearly all regions and seasons, linear trends estimated for both storm indices over the period analyzed show a decrease," while "in terms of the regional average series," they say that "all seasons show statistically significant declines in both storm indices, with the largest reductions in storminess in autumn and winter."

Among the highly publicized changes in weather phenomena that are predicted to attend global warming are increases in the frequency and severity of various types of storms. As the earth has warmed over the last century or more, however, we once again find another example of the fact that this prediction is widely out of sync with reality, as may also be seen is the case for most other parts of the globe by perusing the many materials archived under the various sub-headings of Storms in our Topical Archive.

Additional References
Alexander, L.V. and Power, S. 2009. Severe storms inferred from 150 years of sub-daily pressure observations along Victoria's 'Shipwreck Coast." Australian Meteorological and Oceanographic Journal 58: 129-133.

Rakich, C.S., Holbrook, N.J. and Timbal, B. 2008. A pressure gradient metric capturing planetary-scale influences on eastern Australian rainfall. Geophysical Research Letters 35: 10.1029/2007GL032970.