资源环境科技发展态势分析平台

This study applied statistical change-point analysis to the time series of the Changma retreat date (CRD) on the Korean Peninsula over a recent 30-year period (1985-2014) and detected that the CRD has been delayed by about 10 days since 2000. The average CRD is July 14 for 1985-1999 and July 24 for 2000-2014. Corresponding to the CRD delay, the July rainfall is concentrated in the northern South Korea during 2000-2014, whereas tends to be intense along the southern coast during 1985-1999. The delayed CRD is associated with, in the lower and mid-troposphere, a strengthened cyclonic circulation around Lake Baikal-eastern Sea of Japan and an enhanced anticyclonic circulation in East China Sea. Thus, northerlies from strengthened cyclones and anomalous southerlies from the enhanced anticyclones converge at the northern-central Korean Peninsula. The anomalous anticyclone is associated with the strengthening of the western North Pacific subtropical high that has strengthened in meridional direction in the later epoch, supplying warm and moist air to Korean Peninsula. The result is verified by the enhanced warm and moist anomalous upward flows in the latitude where Korean Peninsula is placed. The delayed CRD in the latter epoch is related to the decreased spring snowfall over East Asia except for the vicinity of the Lake Baikal, which results in severely hot weather in the East Asia continent from spring to July. The continent heating from spring to July weakened (increases), the thermal gradient between continent and ocean, thereby forming a low-pressure system on East Asia and a high-pressure system in western North Pacific, resulting in the strengthening of Changma rain belt in July and delayed the Changma withdrawal.