Interactive influence of ENSO and IOD on contiguous heatwaves in Australia

Abstract

Australian heatwaves have a significant impact on society. Most previous studies focus on understanding them in terms of frequency, duration, intensity, and timing. However, understanding the spatial characteristics of heatwaves, particularly those occurring in contiguous regions at the same time (here referred to as contiguous heatwaves), is still largely unexplored. Here, we analyse changes in spatial characteristics of contiguous heatwaves in Australia during 1958-2020 using observational data. Our results show that extremely large contiguous heatwaves are covering significantly larger areas and getting significantly longer during the recent period (1989/90-2019/20) compared to the historical period (1958/59-1988/89). We also investigated the association of contiguous heatwaves in Australia with interactions of the El Niño–Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) using a large multi-member ensemble of a physical climate model. We found that areal magnitude, total area, median duration, and maximum area of large and extremely large contiguous heatwaves in Australia are significantly higher (lower) during the strong El Niño (Es), strong El Niño co-occurring with strong IOD positive (Es-IPs), and with moderate IOD positive (Es-IPm) (co-occurring strong La Niña with the strong IOD negative (Ls-INs)) seasons relative to the neutral seasons (where both ENSO and IOD are in neutral phase). During the Es, Es-IPm, and Es-IPs seasons, the large-scale physical mechanisms are characterised by anticyclonic highs over the southeast and cyclonic lows over the northwest of Australia, favouring the occurrence and intensification of heatwaves in Australia. These results provide insights into the driving mechanisms of contiguous heatwaves in Australia.

Spatiotemporal Evolution Patterns of Contiguous Extreme Precipitation Events Across China From a 3D Perspective

“…SCEPEs refer to the connected extreme precipitation events that occur synchronously in neighboring regions or consecutively in adjacent days, similar to spatiotemporal contiguous heatwaves as defined in previous studies (Luo et al., 2022; Reddy et al., 2021). These events exhibit the processes of initiating, growing, diminishing, and terminating, evolving across the space and time.…”

“…Then the extreme precipitation days ( P > P95) in neighboring grids within the preceding and ensuing days are connected and marked as a contiguous event (i.e., SCEPE). This spatiotemporally contiguous events tracking (SCET) process is executed by the connected component 3D labeling algorithm (Silversmith, 2021), which has been used in tracking contiguous heatwaves (Luo et al., 2022; Reddy et al., 2021). More details of the SCET process are described in Supporting Information (Figure S1).…”

An Observational Investigation of Spatiotemporally Contiguous Heatwaves in China From a 3D Perspective

“…The CC3D algorithm is an elaboration into 3D images of the 2D image connected components labeling (CCL) algorithm developed by Rosenfeld and Pfaltz (1966), and is implemented in the Python package connected‐components‐3d (https://pypi.org/project/connected-components-3d/). The CC3D method has been used to segment different cells or organs (e.g., kidneys and tumors) in medical studies (O'Reilly et al., 2021; Park et al., 2021; Zhao et al., 2020), and it also demonstrates potential in identifying connected events in climatological research (Reddy et al., 2021). The procedure of the method is briefly introduced as follows by starting with 2D CCL.…”

“…org/project/connected-components-3d/). The CC3D method has been used to segment different cells or organs (e.g., kidneys and tumors) in medical studies (O'Reilly et al, 2021;Park et al, 2021;Zhao et al, 2020), and it also demonstrates potential in identifying connected events in climatological research (Reddy et al, 2021). The procedure of the method is briefly introduced as follows by starting with 2D CCL.…”

Corrigendum: Interactive influence of ENSO and IOD on contiguous heatwaves in Australia (2022 Environ. Res. Lett. 17 014004)

“…We identified an error in calculating the result shown in figure 7 of our recent letter Reddy et al (2021). The error affected the composite difference of detrended mean sea level pressure (MSLP) and geopotential height at 500 hPa (z500) between the strong El Niño (E s ), strong El Niño co-occurring with strong Indian Ocean Dipole (IOD) positive (E s −Ip s ), strong El Niño co-occurring with moderate IOD positive (E s −Ip m ), strong La Niña co-occurring with strong IOD negative (L s −In s ) phases and neutral (El Niño-Southern Oscillation (ENSO) neutral + IOD neutral; NN) phase, respectively.…”