Stratospheric ozone as a driver of the Victorian autumn rainfall variability and trend
Eun-Pa Lim
Victorian autumn-season rainfall experienced a significant decline during the 1990s-2000s. However, identifying the cause of the reduction has been challenging as there is no outstanding relationship between Victorian autumn rainfall and the dominant modes of climate variability such as El Niño-Southern Oscillation, the Indian Ocean Dipole, and the Southern Annular Mode. This study proposes that the Southern Hemisphere stratospheric ozone is a driver of Victorian autumn rainfall variability and trend. We have found a statistically significant relationship between Victorian autumn rainfall and the mid- to lower stratospheric ozone concentrations in 90-50°S, along with concurrent multi-decadal variations. Autumn-season ozone anomalies are linked to the preceding summer ozone anomalies, therefore carrying the signal of the Antarctic ozone depletion trend, which seems to explain the persistent low values of the stratospheric ozone and a part of the Victorian rainfall reduction in autumn in the 1990s-2000s. The multi-decadal autumn rainfall reduction is reproduced by both the NASA GISS Earth System Model and ACCESS-S2 when driven by time-varying observed ozone forcing.
This work will be of interest to climate scientists and model developers and the stakeholders using seasonal forecasts and long-term projections for Australian rainfall.
Key words: Victorian autumn rainfall, Antarctic ozone depletion
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