INTERDECADAL CHANGE OF KOREA LANDFALLING TROPICAL CYCLONE FREQUENCY AND ITS POSSIBLE ASSOCIATION WITH PDO

The present study verified that Korea landfalling tropical cyclone (TC) frequency was rapidly increased since 1981 through the statistical change-point analysis. The increase was due to the formation of anomalous southerlies around Korea from the low latitude ultimately because anomalous cyclone was strengthened in East Asia continent due to the movement of western North Pacific subtropical high (WNPSH) to the east whereas anomalous anticyclone was strengthened in the western North Pacific. The anomalous southerlies played a role in steering flow that moved TCs generated in the subtropical western North Pacific to Korea. In order to determine the cause of strengthening of anomalous cyclone in East Asia continent, a snow depth during the preceding spring (March-May) was analyzed. The analysis result showed that most regions in East Asia had lower snow depth than that before 1981. Thus, anomalous cyclone can be developed in the region during summer due to heating in East Asia continent, which was started from the preceding spring, thereby forming a steering flow of anomalous southerlies that can move TCs into Korea. Furthermore, a correlation analysis between Pacific Decadal Oscillation (PDO) and Korea landfalling TC frequency verified that negative correlation was somewhat stronger after 1981.