Conditional attribution of climate change and atmospheric circulation contributing to the record-breaking precipitation and temperature event of summer 2020 in southern China

Abstract Quantification of the contribution of atmospheric circulation to damaging extreme weather and climate events and the attribution of extreme events in the context of climate change has been gaining worldwide interest. Attribution analysis helps us to better understand the risks associated with the effects of climate change on extreme events. However, the contribution of atmospheric circulation, as well as the influence of climate change, to the record-breaking precipitation event in the middle and lower reaches of the Yangtze River and the concurrent record-breaking hot event in South China during the Meiyu period (June–July) in 2020 are still unclear. In this study, we use flow analogues to estimate how much the atmospheric circulation can explain these two extreme events and the influence of climate change. The results show that the atmospheric circulation explains 70.73% and 43.61% of the extreme precipitation event and the concurrent hot event, respectively. Compared with past climate, the occurrence risk of an event reaching or exceeding the 2020 Meiyu amount under similar atmospheric circulation conditions increased by 5.1 times under the present climate, 80% of which can be attributed to climate change. In addition, hot events similar to the 2020 event cannot occur under past climate, while those reaching or exceeding a one standard deviation threshold increased from 0.58% under past climate conditions to 68.83% under the present climate, 99% of which can be attributed to climate change. These results are beneficial for the understanding and prediction of extreme events in the context of climate change in this region.