Interdecadal variation of Korea affecting tropical cyclone intensity

Abstract

This study analyzed a time series of average central pressure of tropical cyclone (TC) that affected Korea in summer season from 1965 to 2012. To determine whether climate regime shift exists in this time series, statistical change-point analysis was applied to this time series. The result showed that significant climate regime shift existed in 1989, that is, TC intensity from 1965 to 1988 (6588) was weaker than that from 1989 to 2012 (8912). Therefore, an average difference between former and latter periods was analyzed to study large-scale environments, which caused such difference. While TC genesis frequency showed a tendency that TCs in the 6588 period were originated from the northwest quadrant in the tropical and subtropical western North Pacific, TCs in the 8912 period were originated from the southeast quadrant. Thus, it was judged that TCs in the 6588 were generated at a higher latitude followed by moving to Korea, so their strength was weaker than those of TCs of 8912 due to lack of time to acquire sufficient energy from the sea. For TC passage frequency, TCs in the 6588 period showed a tendency to move a short distance from the sea far away from the southeast in Japan to the sea far away from the northeast in Japan or toward the East China Sea. On the other hand, TCs in the 8912 period moved a longer distance from the sea far away from the Philippines via Japan to the eastern sea of Kamchatka Peninsular or toward the east region in China. As such, an average difference of intensity between the former period and the latter period over the 500-hPa streamline was analyzed to determine why the intensity of TCs in the 6588 period was weaker than that of TCs in the 8912 period. As a result, anomalous cold northerlies from anomalous cyclones based on the northern territory of Japan were predominant, while these anomalous flows were originated from the tropical and subtropical western Pacific followed by moving to Korea, thereby affecting the weakening of the TC intensity. Negative anomaly in 500 and 850 hPa air temperature, 600 hPa relative humidity, precipitable water, and sea surface temperature accounted for most of the analysis between the two periods, thereby forming disadvantageous atmospheric environments for strengthening the TC intensity.