The Unprecedented 2023 North China Heatwaves and Their S2S Predictability

• Published in: Geophysical research letters 2024-03, Vol.51 (6), p.n/a
• Main Authors: Xiao, Huiwen, Xu, Peiqiang, Wang, Lin
• Format: Article
• Language: English
• Subjects: Antarctic front; Anticyclones; Atmospheric models; Circulation anomalies; extreme event; Foehn; Foehn winds; Heat waves; heatwave; Heatwaves; High temperature; jet stream; Lead time; Mathematical models; Numerical models; Numerical prediction; Polar fronts; Pressure; Rivers; Rossby wave; Standing waves; sub‐seasonal to seasonal prediction; Surface temperature; teleconnection; Troposphere; Upper troposphere; Upstream; Wave packets; Wave trains
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2023GL107642

This study unravels the characteristics, mechanisms, and predictability of four consecutive record‐breaking heatwaves hitting North China in June and July 2023. The first three heatwaves primarily influenced the northern part of North China and were accompanied by consistent anticyclonic anomalies in the upper troposphere. The anomalous anticyclone was caused by the British–Baikal corridor teleconnection along the polar front jet, particularly during the second heatwave. In contrast, the fourth heatwave was induced by a distinct low‐pressure system, attributed to the Silk Road pattern along the subtropical jet. The presence of this low‐pressure system and its interaction with atmospheric rivers and local topography led to the foehn wind, further contributing to the rise in surface temperatures. Sub‐seasonal to seasonal models can effectively predict the occurrence of all heatwaves 2–5 days in advance despite underestimating the intensity. However, models exhibit limitations in providing reliable predictions when the lead time exceeds 2 weeks. Plain Language Summary In the summer of 2023, North China experienced four consecutive extreme high‐temperature events, which are called heatwaves. This study investigates the main factors that cause the four events and shows how well the operational numerical models can predict the heatwaves. The first three heatwaves shared similar circulation, with high‐pressure systems controlling North China. This local circulation anomaly was related to an upstream quasi‐stationary wave train along the polar front jet. The fourth heatwave was associated with a low‐pressure system over North China and an upstream quasi‐stationary wave train along the subtropical jet. Moreover, predictions from operational models demonstrate their capability to forecast the occurrence of high temperatures 2–5 days ahead, with an underestimation in the intensity. However, models are not reliable when it comes to predicting heatwaves 2 weeks in advance. Key Points North China witnessed record‐breaking heatwaves in June and July 2023, consisting of four sequential synoptic‐scale events The first three and the last heatwaves are controlled by distinct local circulations induced by atmospheric wave trains across Eurasia S2S models capture the heatwave occurrences 2–5 days in advance, but predictive skill notably diminishes beyond 2 weeks