Compound drought and heatwaves (CDHWs) can cause significant socio-economic and ecological impacts. A better understanding of historical spatiotemporal changes of Australian CDHWs and their underlying physical mechanisms can help improve their predictability. We analyse changes in Australian CDHW metrics in the extended summer season (November to March) during the period 1958–2020. Our results suggest that CDHWs increased significantly in terms of their frequency, duration, amplitude, and severity in the recent period (1989/90–2019/20) relative to a historical period (1958/59–1988/89), particularly in eastern Australia. We further analysed the influence of co-occurring modes of El Niño Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) on the frequency and severity of Australian CDHWs using two Coupled Model Intercomparison Project phase 6 (CMIP6) single model initial-condition large ensembles. We found that frequency, duration, and severity of CDHWs are significantly increased during strong El Niño phases across northeast Australia compared to neutral ENSO and IOD conditions. This increase is widespread over northeast and southeast Australia during the concurrence of strong El Niños and moderate-strong positive IOD events. Our results show that an extreme CDHW season in terms of their frequency, duration, and severity occurs one out of every two seasons of strong El Niño over the northeast Australia. Moreover, the same applies for the co-occurring strong El Niño and positive IOD over the northeast and southeast Australia as well. Our results highlight the importance of ENSO and IOD combinations for Australian CDHW events. Our findings provide insights into the importance of climate variability in driving Australian CDHWs.

复合干旱和热浪 (CDHW) 会造成重大的社会经济和生态影响。更好地了解澳大利亚 CDHW 的历史时空变化及其潜在的物理机制有助于提高其可预测性。我们分析了 1958 年至 2020 年期间延长的夏季（11 月至 3 月）澳大利亚 CDHW 指标的变化。我们的研究结果表明，相对于历史时期（1958/59-1988/89），CDHW 在最近时期（1989/90-2019/20）的频率、持续时间、幅度和严重程度显着增加，特别是在东部澳大利亚。我们进一步分析了厄尔尼诺南方涛动 (ENSO) 和印度洋偶极子 (IOD) 共现模式对澳大利亚 CDHW 频率和严重性的影响，使用两个耦合模型比对项目第 6 阶段 (CMIP6) 单模型初始条件大合奏。我们发现，与中性 ENSO 和 IOD 条件相比，在澳大利亚东北部的强厄尔尼诺阶段，CDHW 的频率、持续时间和严重程度显着增加。在强厄尔尼诺现象和中强正 IOD 事件同时发生期间，这种增加在澳大利亚东北部和东南部普遍存在。我们的研究结果表明，就频率、持续时间和严重程度而言，极端 CDHW 季节在澳大利亚东北部每两个强厄尔尼诺季节中出现一个。而且，这同样适用于在澳大利亚东北部和东南部同时发生的强厄尔尼诺现象和正 IOD。我们的结果强调了 ENSO 和 IOD 组合对澳大利亚 CDHW 事件的重要性。我们的研究结果提供了关于气候变化在推动澳大利亚 CDHW 中的重要性的见解。