Atlantic Multi-decadal Oscillation Modulates the Relationship Between El Niño-Southern Oscillation and Fire Weather in Australia

Abstract

Abstract. El Niño–Southern Oscillation (ENSO) is an important driver of fire weather in Australia. The correlation between ENSO and Australian fire weather has strengthened over the recent two decades. However, the causes for this change have not been well investigated. Here, using reanalysis datasets and numerical model simulations, we show that the Atlantic Multi-decadal Oscillation (AMO) could potentially modulate the ENSO-Australian fire weather relationship. The correlation between ENSO and Australia fire weather index (FWI) increases from 0.17 to 0.70 when AMO shifts from its negative phase to its positive phase. This strengthening effect can be explained by the atmospheric teleconnection mechanisms. Specifically, the positive AMO phase, manifested as a warming North and Tropical Atlantic, generates Rossby wave trains and results in high pressures over Australia, which increases local temperature and wind speed but decreases precipitation. This signal superimposes ENSO and thus serves to enhance the ENSO effect on Australian fire weather.