Changes in hourly rainfall return levels due to temperature shifts: global assessment of the TENAX model

Extreme sub-daily precipitation is difficult to anticipate and may cause flash floods, urban floods and debris flows, resulting in casualties and damage to infrastructure, homes, and livelihoods. With increasing temperatures, more moisture can be stored in the atmosphere, which means that there is potential for larger extreme events. Indeed, short-duration precipitation extremes are already increasing in magnitude, and return levels (i.e., magnitudes associated with low exceedance probabilities) are changing. Quantifying extreme short-duration rainfall return levels for the coming years is critical for decision making and for defining insurance premiums. However, the methods we typically use to derive rainfall return levels do not include the physics driving the processes, so they are not suitable for predicting future extremes. The TENAX model was recently proposed to address this issue. It uses knowledge of temperature-precipitation scaling rates and statistics to predict future return levels of short-duration extreme precipitation based on the future temperature shifts. It has been successfully applied to mid-latitude regions, but we do not currently know how it should be parameterized for other climates with different temperature conditions and different processes behind heavy precipitation, such as the tropics. We apply TENAX globally using a global hourly rainfall dataset (GSDR) and ERA5-land reanalysis temperature data. We assess whether the statistical description of precipitation and temperature hold in different climates. Using the longest recording stations, we perform a hind-cast to check the ability of this approach to predict extreme hourly precipitation return levels for the coming decade.