Links between East Coast Lows and the spatial and temporal variability of rainfall along the eastern seaboard of Australia

Abstract

East Coast Lows (ECLs) are intense low-pressure systems which occur over the subtropical east coasts of southern and northern hemisphere continents. ECLs are typically associated with gale force winds, large seas, storm surges, heavy rainfall and flooding. While ECL impacts are typically seen as negative the rainfall associated with ECLs is also very important for urban water security within the heavily populated eastern seaboard of Australia (ESA). This study investigates historical ECLs to gain insights into the timing, frequency, intensity and location of ECL occurrence as well as the magnitude and spatial extent of ECL impacts on rainfall. The different characteristics and impacts associated with different ECL sub-types are highlighted and it is proposed that this spatial and temporal variability in ECL behaviour at least partially explains why the ESA is hydroclimatically different to the rest of Australia and why different locations within the ESA have such different rainfall patterns—and therefore different levels of flood and drought risk. The-se insights are critical to the objectives of the New South Wales government funded Eastern Seaboard Climate Change Initiative (ESCCI), in particular Project 5 which focuses on the water security impacts of ECLs. The results of this work will be used to produce climate-informed stochastic daily rainfall simulations that are more realistic than existing stochastic rainfall simulation methods at preserving the statistics important for catchment-scale hydrology (e.g. clustering of extreme events, long-term persistence, frequency/duration/magnitude of wet and dry spells). These simulated rainfall sequences, that incorporate the spatial and temporal hydroclimatic variability caused by ECLs and other climate phenomena, are important inputs into the hydrological models used to determine current and future urban water security within the ESA.