Extreme climate events, such as floods and droughts, have a significant impact on southern Australia, a region that is of great agricultural and economic importance. Severe heatwaves, which exacerbate drought, are also a common occurrence. While previous work suggests that the annual number of heat waves (HWN) has increased across southern and eastern Australia (Perkins et al. 2012), along with heat wave duration (HWD) across the southeast, future changes in the dynamics that govern southern Australian heatwaves have yet to be assessed. Here we analyse historical and future projections from coupled climate models, that have participated in the Coupled Model Intercomparision Project phase 5 (CMIP5) across different Representative Concentration Pathway (RCP) experiments for the three main capital cities of southern Australia; Adelaide, Melbourne and Perth; where severe heatwaves are most prevalent. While the simulated HWN does not increase over the twentieth century, large increases are simulated towards the end of the twenty-first century, most significantly in the RCP8.5 (high forcing scenario) runs. The increases in HWN are also accompanied by an increase in HWD, leading to a significant increase in the proportion of days classified as heat wave days, based on the historical 1950-2005 baseline.  The largest increase in heatwaves are projected during austral winter (June, July, August). In this presentation we will elucidate the dynamical factors behind the projected changes to southern Australian heatwaves.

References:

Perkins, S. E., L. V. Alexander, and J. R. Nairn (2012), Increasing frequency, intensity and duration of observed global heatwaves and warm spells, Geophys. Res. Lett., 39, L20714, doi:10.1029/2012GL053361.