The timing of extreme rainfall events in Australia and variability associated with the IPO — Australian Meteorological and Oceanographic Society
  1. Schedule
  2. 34(i). Rainfall processes, prediction and extremes
  3. The timing of extreme rainfall events in Australia and variability associated with the IPO

The timing of extreme rainfall events in Australia and variability associated with the IPO (#222)

Raktima Dey 1 2 , Margot Bador 3 , Lisa V Alexander 3 , Sophie C Lewis 4
  1. ARC Centre of Excellence for Climate System Science, UNSW, Sydney
  2. Australian National University, Canberra, ACT, Australia
  3. School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW, Australia
  4. University of New South Wales-Australian Defence Force Academy, Canberra, ACT, Australia

Australia experiences one of the world’s highest rainfall variability. Part of the reason behind such high variability is various large-scale drivers such as the El Niño-Southern Oscillation (ENSO), the Interdecadal Pacific Oscillation (IPO), the Southern Annular Mode (SAM), the Indian Ocean Dipole (IOD) that impact Australia’s rainfall thus making the seasonal prediction of mean and extreme rainfall challenging. Previous studies focus primarily on the relationship between large-scale drivers and mean and extreme rainfall intensities. The IPO, for example, plays a crucial role in modulating Australia’s rainfall, where a negative phase is associated with stronger ENSO-Australian rainfall relationship while during a positive phase, the relationship weakens. These results hold for both mean and extreme rainfall.  To our knowledge, there have not been studies yet looking at the relationship between the large-scale drivers and the timing of when extreme rainfall events occur. In this study, we calculate annual maximum five consecutive day (rx5) rainfall. Next, we take the first day of the rx5 event and calculate the month in which it occurred at every grid point over the period 1911-2016 using the AWAP data. Next, we investigate the following questions:

  1. What is the median month in which extremes generally occur in different regions in Australia? Is the season in which extremes occur changing?
  2. What is the relationship between the season in which the extreme rainfall occurs and ENSO, and how does it interact with the IPO?

Overall understanding the relationship between extreme rainfall seasonality and large-scale climate drivers could potentially improve the seasonal prediction of extremes. This approach can be used in other regions in the world to understand the relationship between extreme season and various important drivers.

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