Phase‐Locked Rossby Wave‐4 Pattern Dominates the 2022‐Like Concurrent Heat Extremes Across the Northern Hemisphere

• Published in: Geophysical research letters Vol. 51; no. 4
• Main Authors: Yang, Xiaoye, Zeng, Gang, Zhang, Shiyue, Iyakaremye, Vedaste, Shen, Cheng, Wang, Wei‐Chyung, Chen, Deliang
• Format: Journal Article
• Language: English
• Published: Washington John Wiley & Sons, Inc 28.02.2024; Wiley
• Subjects: concurrent heat extreme; Extreme heat; Geologi; Geology; Heat; Heat waves; Latitude; Northern Hemisphere; Planetary waves; Probability theory; Radiation; Radiation measurement; Rossby waves; summer; Weather patterns; Northeast Asia; Northern Hemisphere; Central Asia; Eastern Europe; North America
• DOI: 10.1029/2023GL107106
• ISSN: 0094-8276; 1944-8007

Concurrent heat extremes (CHEs) are becoming increasingly common in the mid‐high latitudes across the Northern Hemisphere (NH), underscoring the need to comprehend their spatiotemporal characteristics and underlying causes. Here we reveal a phase‐locking behavior in Wave‐4 pattern, particularly after mid‐1990s, giving rise to a prominent CHE mode akin to heat extreme pattern observed in 2022, which swept most NH regions. Wave‐4 pattern significantly amplifies the likelihood of CHEs in Eastern Europe (∼30%), Northeast Asia (∼25%), and northwestern coast of North America (∼15%), while reducing the likelihood in central North America and northern Central Asia. During 1979–2022, the identified pattern accounted for over 69.7% of the trends in heat extremes over the mid‐high latitudes of the NH, directly exposing approximately 333.5 million people to heat extremes. Observations and simulations indicate that radiation anomalies over Eastern European Plain and West Siberian Plain play pivotal roles as primary forcing sources for Wave‐4 pattern. Plain Language Summary Researchers have found that concurrent heat extremes are becoming more common in the Northern Hemisphere. This study discovered that a specific weather pattern, called as Wave‐4, became more prominent after the mid‐1990s and is linked to these heat extremes. This pattern increases the probability of heatwave occurrences in Eastern Europe, Northeast Asia, and northwestern coast of North America while decreasing them in central North America and northern Central Asia. Between 1979 and 2022, the identified Wave‐4 pattern contributed to more than two‐thirds of the increase in heat extremes in the northern hemisphere, affecting around 333.5 million people. It is also determined that unusual radiation levels over the Eastern European Plain and West Siberian Plain are significant factors contributing to the Wave‐4 pattern. This information helps us better understand the causes and characteristics of heat extremes in different parts of the world. Key Points The Phase‐locked Rossby wave‐4 pattern dominates the concurrent heat extremes across the Northern Hemisphere The identified pattern exposed approximately 333.5 million people to heat extremes Radiation anomalies over the Eastern European Plain and West Siberian Plain play pivotal roles as forcing sources of the pattern