Cluster Analysis of the Recent Interdecadal Variation in the Tripole Landfall Pattern of Tropical Cyclones in East Asia

Along the East Asian coast, the interdecadal variation in tropical cyclone (TC) landfall activities in the early 2010s shows a tripole change pattern characterized by significantly increased (decreased) TC landfalls to the north of 30 degrees N and to the south of 20 degrees N (between 20 degrees and 30 degrees N). The increased TC landfalls in the East Asian subregion north to 30 degrees N mean greater TC damage in the most populous regions, including southeastern China, the Korean Peninsula, and Japan, since the early 2010s. The present work uses an objective clustering technique to analyze the internal dynamical causes of this interdecadal variation. The increased TC landfall activities in the East Asian subregion north of 30 degrees N are attributed to the increase in TCs with a northwestward-moving track (cluster defined as C1), whereas the increased TC landfall activities to the south of 20 degrees N and the decrease between 20 degrees and 30 degrees N are mainly due to the southward shift of TCs with a westward-moving track (cluster defined as C2). This work focuses on different TC track groups (C1 and C2) based on daily data, showing that the interdecadal changes in the synoptic-scale monsoon trough and subtropical high provide important environment for different groups of TCs. The ascending phase of the PDO with significant warming over the central Pacific favors the interdecadal tripole changes in TC landfalls.