Monday, 12 January 2004
Role of Tropical Cyclone in Southern China on the Heavy Rainfall over Korea
The Korean peninsula experiences annually about five events of heavy rainfall r during the East-Asian summer monsoon period, which is directly or indirectly related to the tropical cyclone. Among the events that are not directly affected by the tropical cyclone, disastrous heavy rainfall over the Korean peninsula has often been accompanied by a tropical cyclone landed in southern China. This tropical cyclone has been qualified to be a key factor to transport moisture into the peninsula, together with a well organized mid-latitude baroclinic system to provide a rising branch over the region of heavy rainfall. However, the importance nd role of the tropical cyclone in southern China to the onset and maintenance of heavy rainfall over Korea has not been dynamically identified. In this study, the Pennsylvania State University-National Center for Atmospheric Research (PSU/NCAR) Mesoscale Model Version 5 (MM5) is utilized to quantify the role of the tropical cyclone landed in southern China on the heavy rainfall over Korea. To this end, a hurricane initialization algorithm of the Geophysical Fluid Dynamics Laboratory (GFDL) is utilized to control the intensity of tropical cyclone in southern China.
Numerical model results show that the effect of remote forcing due to the typhoon in southern China is crucial to the maintenance of heavy rainfall over Korea. Without the tropical cyclone landed in China, the precipitation over Korea is significantly reduced by more than a factor of half. This indicates that the low-level jet on the right side of the cyclone transports warm and moist air from southern China to the Korean peninsula. Interestingly, the typhoon bogussed with a stronger intensity than the observed central pressure is found to play a negative role in initiating the heavy rainfall over Korea. A stronger typhoon than the observed is found to be decoupled with a mid-latitude synoptic system over the heavy precipitation area in Korea since it tends to move further westward.