Future Australian severe thunderstorm environments. Part B: The influence of a strongly warming climate on convective environments
John T. Allen,1,2 David J. Karoly1 and Kevin J. Walsh1
1 School of Earth Sciences, The University of Melbourne, Victoria, Australia
2 International Research Institute for Climate and Society, The Earth Institute, Columbia University, New York, USA
Abstract
The influence of a warming climate on the occurrence of severe thunderstorm environments in Australia was explored using two global climate models: CCAM and CSIRO Mk3.6. These models have previously been evaluated and found to be capable of reproducing a useful climatology for the 20th century period (1980 to 2000). Analyzing the changes between the historical period and high warming climate scenarios for the period 2079 to 2099 has allowed estimation of the potential convective future for the continent. Based on these simulations, significant increases to the frequency of severe thunderstorm environments will likely occur for northern and eastern Australia in a warmed climate. This change is a response to increasing convective available potential energy from higher continental moisture, particularly in proximity to warm sea-surface temperatures. Despite decreases to the frequency of environments with high vertical wind shear, it appears unlikely that this will offset increases to thermodynamic energy. The change is most pronounced during the peak of the convective season, increasing its length and the frequency of severe thunderstorm environments therein, particularly over the eastern parts of the continent. The implications of this potential increase are significant, with the overall frequency of potential severe thunderstorm days per year likely to rise over the major population centers of the east coast by 14% for Brisbane, 22% for Melbourne and 30% for Sydney. The limitations of this approach are then discussed in the context of ways to increase the confidence of predictions of future severe convection.
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