Local sea surface temperatures add to extreme precipitation in northeast Australia during La Niña.

This study examines the role played by high sea surface temperatures around northern Australia, in producing the extreme precipitation which occurred during the strong La Niña in December 2010. These extreme rains produced floods that impacted almost 1,300,000 km2, caused billions of dollars in damage, led to the evacuation of thousands of people and resulted in 35 deaths. Through the use of regional climate model simulations the contribution of the observed high sea surface temperatures to the rainfall is quantified. Results indicate that the large-scale atmospheric circulation changes associated with the La Niña event, while associated with above average rainfall in northeast Australia, were insufficient to produce the extreme rainfall and subsequent flooding observed. The presence of high sea surface temperatures around northern Australia added ~25% of the rainfall total.

Figure 3: Evans plot of the CTL ensemble mean 20 to 30 December precipitation (hue) and the non-parametric Mann-Whitney U test probability that this is not from the precipitation distribution produced by the LNM ensemble (saturation/intensity). The darkest colors are more than 99% probable, and the brightest colors are between 95% and 99% probability.