April 14, 2021 | Published by | , , ,

Picture: Earth Observations “Islands In The Sky”. Credit: NASA.

With the recategorization of our research programs, modelling research has now become a program of its own even though it underpins and works with every other research program. A key focus of this program is the development of Australia’s ACCESS model.

As part of this focus our researchers analysed the performance of the ACCESSS1 seasonal forecast model to predict the South Pacific Convergence Zone position and rainfall over the period 1990-2012. ACCESSS1 performed better in simulating the Convergence Zone than the previous model, POAMA. However, there are still challenges, including simulating extreme zonal South Pacific Convergence Zone events, which often occur during strong eastern Pacific El Nino events.

Another important part of the modelling process is to make the data produced by climate models as accessible as possible. Output from the world’s most comprehensive climate models requires specialist skills to process, even for seemingly routine tasks such as calculating global-mean temperature projections. This prevents it from being used as widely as it should be. To solve this, CLEX researchers have done the calculations and have made the outputs available in a newly published dataset. As a brief overview, the dataset consists of spatial and regional means, such as global-mean temperatures, or rainfall over south-east Australia, derived from the latest CMIP6 climate model experiments. The outputs are available via a web portal in a text-based format which can be used by any well-known data analysis tool.

Data around heat events tends to be more consistent and reliable, so the Modelling team used statistical techniques to investigate changes in extreme climate events that currently occur, on average, only once every 20 years. These techniques were applied to data related to heat, rainfall, drought and conditions conducive to bushfires and thunderstorms from detailed climate modelling commissioned by NSW and ACT Governments. Overall, the results showed an increase in the frequency of extreme conditions across the majority of southeast Australia by the end of the 21st century. This was true for all of the different types of extremes considered but was especially conclusive for heat extremes and conditions conducive to thunderstorms. Several cities were projected to experience some extremes more than six times more frequently at the end of the century than under current climate conditions. The study is an exemplar of the use of detailed climate modelling to assess future changes in potentially damaging climate extremes. It reveals relevant limitations in climate modelling and analysis techniques. Although, it does not address the issue of coincident climate extremes, which are often responsible for the most damage to communities and infrastructure, it provides information relevant to planning for managing future climate risks.

Our researchers also introduced a novel methodology to examine the Southern Ocean’s response to changing winds. This is an important region for understanding future climate change as the atmospheric winds over the Southern Ocean play a leading role in its ability to uptake heat, by way of driving much of the Southern Ocean circulation. They performed numerical simulations with a global ocean‐sea ice model suite that spans a hierarchy of spatial resolutions and driven by realistic atmospheric forcing conditions. The initial response of the Southern Ocean circulation to changes in winds is robust across the model suite and insensitive to model resolution; longer‐term response, however, depends on the representation of eddies in the model.

Working with models and complex coding is the basis of our research but the journey to reach the point often begins at a young age. Paola Petrelli may have inspired some students to begin that journey when she volunteered to help with a python coding course for grade-5 and grade-6 at Albuera St Primary School, Hobart. Meanwhile, we have welcomed new students to our research program who are already on that journey with Chenhui Wang beginning a Masters degree with CLEX and Ashley Barnes starting a PhD. Both are supervised by Andy Hogg.