Reanalyzing the Relationship of Tropical Cyclone Frequency and Intensity Affecting South Korea with the Pacific Decadal Oscillation

Several studies have reported a significant negative correlation between the tropical cyclone (TC) frequency affecting South Korea (KOR TC frequency) and the Pacific decadal oscillation (PDO), which is accompanied by the weak negative correlation between the TC intensity when TCs enter Korean coastal seas (KOR TC intensity) and PDO. However, the weak negative relationship between KOR TC intensity and PDO contradicts results from other related studies regarding the relationship between TC activity in the western North Pacific and PDO. Thus, we reexamined the PDO relationships with both KOR TC frequency and intensity and their mechanisms. Although a negative correlation between KOR TC frequency and PDO was consistently found, in contrast to previous studies, we found a significant positive correlation between KOR TC intensity and PDO. According to our analyses, during the negative phase, anomalous southeasterly winds over the Korean Peninsula and the northwestward shift in the mean TC genesis location favor the increase in KOR TC frequency. The northwestward mean TC genesis location migrates, which shortens the time spent over the warm ocean, weakening the lifetime maximum intensity and, consequently, the KOR TC intensity. We confirmed that our result is robust by performing various sensitivity tests examining the best track data, analysis period, TC season, and KOR TC definition.