Since our last report, the Extreme Rainfall Research Program held a foundational workshop with 30 key researchers and stakeholders from our partner universities, the Bureau of Meteorology, CSIRO, NSW Office of Environment & Heritage, and the National Center for Atmospheric Research. The workshop focused on the Centre’s four main projects in extreme rainfall, with 10-minute overview talks followed by deep discussion into plans for accomplishing our goals. At the end of the day there was a broad discussion as to whether there were any gaps in the program. You can find a report of the workshop and some of its outcomes, here.
The Extreme Rainfall program also launched its first Citizen Science application, WeatheX. One of the great challenges of studying extreme rainfall events and their constituent parts – like hail, wind, tornadoes and flooding – has been the spotty nature of these events. A flash flood from a large squall can occur 10km away from an area that doesn’t get a drop of rain.
The distance between most meteorological instruments means that on-the-ground measurements are often incomplete. At the same time, while radar images are useful, they cannot tell the complete story of an extreme rainfall event.
The WeatheX app aims to get citizen scientists to record wind, hail, flooding and even tornadoes on mobile devices as or shortly after they occur. These on the ground observations can then be combined with radar images.
With this additional information, it opens avenues for research that may help us better understand and forecast extreme rainfall events. The first example of this process in action was the Brisbane storms on Sunday, October 21. You can see the overlap of observations and Bureau of Meteorology radar images below.
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We should also highlight the individual triumph of Associate Investigator Caroline Ummenhofer who in September was named as a winner of the AGU James B. Macelwane Medal. This prestigious medal is awarded to an early career researcher within 10 years of their PhD, and includes becoming an AGU Fellow in their own right.
Chief Investigator Prof Christian Jakob has also been awarded the Australian Meteorological and Oceanographic Society’s Morton Medal for leadership in meteorology, oceanography, climate and related fields, particularly through education and the development of young scientists, and through the building of research environments in Australia.
Congratulations are also in order for Associate Investigator Daniel Argüeso, who has been made editor of a special edition of the journal Atmosphere on the Effects of Urban Areas on Climate Change Conditions, which will be released in 2019.
Meanwhile, Partner Investigator Harry Hendon was named by The Australian newspaper as Australia’s leader in atmospheric science as part of its annual Research Magazine.
We also welcomed a number of international visitors. Dr Wojciech Grabowski, a PI in the Centre and Senior Scientist at NCAR, visited UNSW and the University of Melbourne in early October. Dr Jun-Ichi Yano, Directeur de Recherche at CNRM, Meteo, France, visited our University of Melbourne and Monash nodes in late October.
The UKMO, with support from its international partners, held a convective scale modelling workshop in Darwin in early November. The focus of the workshop was on the ongoing development and evaluation of very high-resolution regional versions of the Unified Model (the atmospheric component of ACCESS). A number of CLEX affiliates attended the workshop, presenting work on modelling convection over the Darwin region at sub-km resolution. The workshop sparked many interesting discussions and identified many opportunities for ongoing collaboration.
In some fascinating research, members of the Extreme Rainfall team looked at dimethyl sulfide (DMS) produced by phytoplankton and how it contributes to atmospheric aerosols. Aerosols are important for cloud formation but natural aerosol emissions remain one of the largest sources of uncertainty in climate models.
The study found important regional consequences for precipitation and cloud formation if large changes in DMS emissions were to occur. As an example of the impact of these emissions, the researchers found that if all DMS were to cease, global average temperatures would rise by 0.5°C over ten years. This has suggested a better understanding of DMS and marine aerosols in general will be needed to improve climate models.
In another piece of research aimed at improving climate models, the Extreme Rainfall group performed fine-scale simulations of tropical thunderstorms over the island of Sumatra. The researchers aimed to better understand how heat is released from tropical thunderstorms. Heat release is influenced by a myriad of factors, including steep mountains, coastlines, time of day and mostly unseen atmospheric waves that move around the planet.
Working at a fine detail that reproduced cloud physics, they found significant variation in rainfall as planetary scale waves passed through the region. Intriguingly, they also found that the interaction between cloud processes, geography and time of day also affected the way planetary waves themselves developed.
These smaller processes are not well represented in climate models, so the next step is to compare the finer simulations with global climate models to find what may be missing and improve the performance of climate models overall.
Some work has also been done on how robust future changes in extreme precipitation over land are across climate models. Results show that models that share atmospheric physics schemes tend to produce similar results. When this is taken into consideration future annual extreme precipitation intensity increases in the majority of models and over the majority of land areas.
Models show more similarities in dry compared to wet regions, in the dry season compared to the wet season and in the extra-tropics compared to the tropics. For each model, the future increase in the wettest day of a season or year exceeds the range of that can be explained by natural variability and this result is particularly robust in the extra-tropics.