Extreme precipitation was expected to increase with increasing temperature and the Clausius-Clapeyron relationship was initially used to estimate future changes including for some design rainfall applications currently in use. However, some recent observational studies have reported scaling rates for sub-daily precipitation at double or even greater than the Clausius-Clapeyron rate of 7% C˚^-1, highlighting a need to consider potential rainfall extremes larger than some design rainfall allowances for our warming climate. Moisture availability, vertical velocity and storm size have all been shown to affect the scaling rate (Lochbihler et al., 2017; Pfahl et al., 2017; Prein et al., 2017).

In this study we examined the changes in hourly extreme precipitation from the observation record in Victoria from 1958 to present. We found that the number of extreme precipitation events, the 99^th percentile of precipitation and the proportion of precipitation from extreme events are all increasing. Additionally, there is some indication that the rates of increase of these metrics are accelerating. We also found that the most extreme precipitation events examined were increasing at the fastest rates, particularly during the warm season.

We will also categorise extreme precipitation events by storm types and present the temperature scaling rates for the different storm types.

Lochbihler, K., Lenderink, G., & Siebesma, A. P. (2017). The spatial extent of rainfall events and its relation to precipitation scaling. Geophysical Research Letters, 44(16), 8629-8636.

Pfahl, S., O’Gorman, P. A., & Fischer, E. M. (2017). Understanding the regional pattern of projected future changes in extreme precipitation. Nature Climate Change, 7(6), 423.

Prein, A. F., Rasmussen, R. M., Ikeda, K., Liu, C., Clark, M. P., & Holland, G. J. (2017). The future intensification of hourly precipitation extremes. Nature Climate Change, 7(1), 48.