Rainfall events become temporally more uniform with increasing storm depth

• Rainfall events generally become temporally more uniform with increasing magnitude. • This relationship is consistent in both observed data and areal reanalysis. • The rate of increase in temporal uniformity varies spatially and with event duration. • The increase in temporal uniformity holds for even the rarest rainfall bursts. When undertaking hydrologic modelling for design of infrastructure, storms of varying rainfall depths and durations are generated for event-based models by combining univariate distributions of rainfall depths and rainfall temporal patterns. Flood characteristics, especially peak flows, are sensitive to the temporal pattern of the causative rainfall, however there is limited research on how the temporal uniformity of these patterns might change with event severity. Here we investigate how the uniformity of rainfall temporal patterns varies with rainfall magnitude. This analysis was conducted for Australia, which spans a wide variety of meteorological conditions. Three country-wide datasets were used: sub-daily point rainfall observations, daily gridded rainfall observations, and sub-daily gridded rainfalls from modelled reanalyses. Using each of these datasets, storms of different durations were identified, and regression relationships were established between rainfall depths over the entire duration of the storm and rainfall depths that occurred within fixed subset periods embedded in the storm. Regression relationships were derived for each pixel in the two gridded datasets, and for each gauge in the sub-daily point observation dataset. It was found that rainfall bursts become temporally more uniform with increasing storm depth. This finding was consistently observed for different storm durations across each of the three datasets, though the strength of the relationship varied spatially across Australia. This relationship was also observed when considering the regional maximum rainfall bursts across meteorologically homogeneous zones, implying the relationship also holds for extreme storms. A numerical experiment was undertaken using synthetic data for a range of distributional characteristics, and the results obtained were found to be consistent with those based on observed data. This increase in temporal uniformity with storm depth highlights the need to vary design inputs with the storm magnitudes of interest.