Eliminating the Hook in Precipitation-Temperature Scaling

Observational studies of extreme daily and subdaily precipitation-temperature sensitivities (apparent scaling) aim to provide evidence and improved understanding of how extreme precipitation will respond to a warming climate. However, interpretation of apparent scaling results is hindered by large variations in derived scaling rates and divergence from theoretical and modeled projections of systematic increases in extreme precipitation intensities (climate scaling). In warmer climatic regions, rainfall intensity has been reported to increase with temperature to a maximum before decreasing, creating a second-order discontinuity or hook-like structure. Here we investigate spatial and temporal discrepancies in apparent scaling results by isolating rainfall events and conditioning event precipitation on duration. We find that previously reported negative apparent scaling at higher temperatures that creates the hook structure is the result of a decrease in the duration of the precipitation event, and not a decrease in the precipitation rate. We introduce standardized pooling using long records of Australian station data across climate zones to show average precipitation intensities and 1-h peak precipitation intensities increase with temperature across all event durations and locations investigated. For shorter-duration events (<6 h), average precipitation intensity scaling is in line with the expected Clausius-Clapeyron (CC) relation at similar to 7 % degrees C-1, and this decreases with increasing duration, down to 2% degrees C-1 at 24-h duration. Consistent with climate scaling derived from model projections, 1-h peak precipitation intensities are found to increase with temperature at elevated rates compared to average precipitation intensities, with super-CC scaling (10%-14% degrees C-1) found for short-duration events in tropical climates.

Automated summary

Observational studies on extreme daily and subdaily precipitation-temperature sensitivities to a warming climate show that rainfall intensity generally increases with temperature to a maximum before decreasing, creating second-order discontinuities or hook-like structures. However, these patterns are influenced by event duration and location, with precipitation rate often decreasing due to shorter event durations. Average precipitation intensity scaling follows expected Clausius-Clapeyron relations, while 1-h peak precipitation intensities exhibit super-CC scaling in tropical climates.