Multiscale Influences on Rainfall in Northeast Australia

This study examines the multiscale modulation of mean and extreme rainfall in Northeast (NE) Australia un-der different background modes of variability, which is a new aspect given the high-resolution and long-term observational datasets. Daily rainfall probability is significantly modified by the Madden-Julian oscillation (MJO), and its influence varies with the seasons and is associated with atmospheric circulation anomalies. Rainfall generally decreases during El Niilo and in-creases during La Niila years; however, there is a notable spatial nuance to El Niilo-Southern Oscillation (ENSO)-associated extreme rainfall, with some locations showing the opposite precipitation response to the typical ENSO-rainfall relationship. Despite more precipitation overall in La Niila years, the mean and extreme precipitation responses to the MJO appear to be stronger and more often statistically significant during El Niilo compared to La Niila periods. The impact of ENSO on the MJO-rainfall relationship is stronger than the variation of the MJO itself with ENSO, and likely reflects a change in the MJO modulation of rain-bearing atmospheric processes. During El Niilo periods, diurnal rainfall amplitude is generally stronger in the central and southern subtropical parts of the study area than during La Niila periods, while the opposite tendency occurs in the northern tropical part. The diurnal cycle of both mean and extreme precipitation is amplified during suppressed convec-tion phases compared to enhanced convection phases of the MJO. In general, the peak time of diurnal cycle does not change with MJO regimes, but there are some notable differences in rainfall propagation between enhanced and suppressed MJO phases.