Role of North Atlantic warming in the extremely hot summer of 2023 in North China

In the summer of 2023, North China experienced a severe and extreme heatwave that lasted for longer than the heatwaves occurring in other areas during this period and longer than any other North China heatwave between 1959 and 2023. During the event, an anomalous long-lived anticyclone dominated the North China region, which formed an extreme heatwave that persisted for more than 20 days. This long-lived anticyclone belonged to a Rossby wave train that originated in the Atlantic and propagated eastward to the East Asian coast. Although the Indian Ocean, Pacific Ocean, and Atlantic Ocean all experienced anomalous heating in 2023, the Atlantic SST anomalies played a dominant and decisive role in the extreme North China heatwave. Both observations and numerical simulations demonstrated a close relationship between Atlantic SST warming and the anomalous anticyclone and heatwaves in the region of North China, a relationship that was not observed or simulated for other oceans.

Atlantic SST warming in the summer of 2023 has a positive contribution to the North China heatwave. Whether there are other factors that contribute to the North China heatwave in 2023 is still unknown. The Atlantic SST warming can indeed provide a necessary anomalous anticyclone and lead to a persistent heatwave event. But other factors, such as urban heat islands, irrigation, may enhance the intensity of the heatwave of 2023 in North China, which needs further study. Moreover, the North Atlantic is experiencing a warming trend owing to global warming. Extreme warming of the North Atlantic in the summer of 2023 was likely caused by both global warming and natural variability. However, the relative contributions of anthropogenic activity and natural variability to North Atlantic warming and therefore the North China heatwave of 2023 remain unknown and require further study.