Relationship between two types of heat waves in northern East Asia and temperature anomalies in Eastern Europe

In this study, the hierarchical clustering algorithm was used to cluster the summer heat waves (HWs) in northern East Asia (NEA) into wave-train HW and blocking HW. In the past 38 years, the wave-train HWs have increased significantly, while the blocking HWs have not shown a visible trend. The wave-train index and the blocking index are proposed to objectively identify the HW type after capturing the circulation characteristics of two kinds of HWs. When a wave-train HW occurs in NEA, simultaneous HW will occur in Eastern Europe. However, when a blocking HW occurs in NEA, a negative temperature anomaly will take place in Eastern Europe. The results of numerical simulations using the linear baroclinic model indicate that the wave-train HWs and the blocking HWs are related to the heating anomaly over southern Greenland and the cooling anomaly over the Barents Sea, respectively.

Automated summary

In this study, the hierarchical clustering algorithm was used to classify summer heat waves (HWs) in northern East Asia (NEA) into wave-train HW and blocking HW. Over the past 38 years, the wave-train HWs have increased significantly, while no clear trend was observed in blocking HWs. The development of wave-train and blocking indices facilitated the objective identification of HW types and circulation characteristics. Numerical simulations using a linear baroclinic model revealed that wave-train HWs are associated with a heating anomaly over southern Greenland, while blocking HWs are linked to a cooling anomaly over the Barents Sea.