More profound impact of CP ENSO on Australian spring rainfall in recent decades

Abstract

Most of Australia was in severe drought from 2018 to early 2020. Here we link this drought to the Pacific and Indian Ocean sea surface temperature (SST) modes associated with Central Pacific (CP) El Niño–Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD). Over the last 20 years, the occurrence frequency of CP El Niño has increased. This study extends the previous understanding of eastern Pacific (EP) El Niño-Australian rainfall teleconnections, exhibiting that CP El Niño can bring much broader and stronger rainfall deficiencies than EP El Niño during austral spring (September–November) over the northern Australia (NAU), central inland Australia and eastern Australia (EAU). The correlations between SST fields and rainfall in three Cluster regions divided by clustering analysis also confirm this, with rainfall variability in most of Australia except southern Australia (SAU) most significantly driven by CP ENSO. Also, we demonstrate that the CP El Niño affects rainfall in extratropical EAU via the Pacific-South American (PSA) pattern. While the influence of EP El Niño is only confined in tropical NAU because its PSA pattern sits far too east to convey its variability. With the development of ENSO diversity since 2000, the footprint of El Niño on Australian rainfall has become more complex.

Associations between Australian climate drivers and extreme weekly fire danger

“…In addition, the indices used by the Bureau are well researched and known to have high relevance for explaining Australian climate variations. For instance, the relevance of the NINO-3.4 index for defining variation in the ENSO is supported by findings that Australian rainfall is more strongly affected by sea surface temperatures (SSTs) towards the central Pacific Ocean as opposed to the previously used NINO-3 region in the eastern Pacific (Wang and Hendon 2007;Ma et al 2022). Other ENSO indices also show strong correlations with Australian rainfall (Risbey et al 2009) and there are opportunities for further investigation into the effects of these, and of alternative indices for other drivers, on the probability of extreme PFI.…”

Evaluation of seasonal teleconnections to remote drivers of Australian rainfall in CMIP5 and CMIP6 models

“…The ability to simulate CP and EP El Niños is important, as both flavours have been shown to have distinct impacts, particularly on Australian rainfall (e.g. Taschetto and England 2009;Santoso et al 2019;Ma et al 2022). Previous generations of models struggled to simulate two distinct regions of equatorial SST warming, with most favouring warming along the eastern Pacific (Taschetto et al 2014;Feng et al 2020).…”

“…In recent years, the important role that ENSO diversity plays on seasonal teleconnections to Australian rainfall has been highlighted (e.g. Freund et al 2019;Santoso et al 2019;Ma et al 2022). Most previous studies focused on the impacts of El Niño diversity on Australian rainfall, with CP El Niños associated with more drying due to the proximity of the SST anomaly.…”

“…These distinct anomaly patterns generate different rainfall responses over Australia, with CP El Niños causing significantly drier conditions than EP El Niños (e.g. Taschetto et al 2010;Yeh et al 2018;Santoso et al 2019;Ma et al 2022). Additionally, there is an asymmetry, or non-linearity in the strength of ENSO events, with El Niño events being stronger than La Niña events, particularly in the eastern Pacific (e.g.…”