Many observational studies have found that short duration (hourly and below) precipitation extremes have been increasing in intensity faster than longer duration extremes. In many cases these short duration extremes are increasing much faster than expected based on the Clausius-Clapeyron relationship. In urban environments these short duration extremes are often responsible for flash flood events. A study over Sydney found that 10 minute
precipitation extremes have increased in intensity by ~40% over the last 20 years. This is a very large and surprising increase. It is currently unknown whether this increase is unique to Sydney or is occurring in other locations, what mechanisms are responsible for this change, and whether we should expect this trend to continue into the future. This project uses coordinated, convection permitting, regional climate downscaling experiments to investigate how short duration (hourly to sub-hourly) precipitation extremes have been changing over major Australian and New Zealand cities and how are they projected to change due to global warming?
The project will be split into two main activities. The first activity will take an event based approach using reanalysis boundary conditions to investigate model skill when simulating these short duration extremes, evaluating them against observations from automatic weather stations and a network of weather radars, and convective-scale reanalysis. These events will also be simulated within a pseudo-global warming framework to explore how they would develop in a future warmer world. The second activity will focus on long-duration simulations at convection permitting resolutions to investigate the modelled changes in these SHEP events. This activity will include both reanalysis driven and CMIP6 GCM driven simulations. The simulations for activity 2 will take longer and use much more resources than activity 1 but they will also allow a more comprehensive assessment of future changes in these events including changes in their frequency not addressed in activity 1. Stakeholders involved include the Australian Bureau of Meteorology (wants to improve the forecasting of these events and reliability of flash flood warnings), State Emergency Services (who are early responders to flash flood events), as well as the Australian Climate Service and the National Environmental Science Program Climate Systems Hub who work with various stakeholders performing climate change risk assessments.
The applicant group contains multiple institutional groups within Australia and New Zealand.
