Projections of Australian low pressure systems in downscaled CMIP6 models

Low pressure systems are associated with a number of climate hazards in Australia, including heavy rainfall, strong winds and coastal erosion. Here, we use a new ensemble of 40 CMIP6 (Sixth Coupled Model Intercomparison Project)-based regional model projections to assess future changes in low pressure systems across Australia, with a focus on vertically developed (deep) cyclones that extend between the surface and 500 hPa. Results show robust future declines in extratropical lows in southern Australia throughout the year, with large uncertainty for lows in northern Australia. Projections for strong, rapidly intensifying and slow-moving low pressure systems are also assessed, and are all projected to decline in frequency. The strongest declines in lows are identified for models that also have larger increases in the intensity of 500-hPa zonal winds to the south of Australia (40–50°S), with observed trends in both indices at the high end of the model range. This suggests the potential for constraining future projections of Australian low pressure systems based on monthly mean zonal winds.