The Relationship Between Persistent Heavy Rainfall Events Over The Yangtze River Valley And Preceding OLR

Based upon identifying the persistent heavy rainfall events (the PHR events) during the period of 1951-2004, the revealed characteristics of the PHR events motivate us dividing Mid-Eastern China into three sub-regions, Yangtze-Huai River valley, Yangtze River valley and South of the Yangtze River, to quantify significant lag-correlations of the rainfalls with global Outgoing Longwave Radiation (OLR) and to study the convection's predominant mid-term role in forcing the PHR events in Mid-Eastern China. Result obtained is that the PHR events in these three regions are highly associated with the prophase of OLR anomaly. The main regions affect PHR events in Yangtze-Huai River valley are tropical western Pacific warm pool, Indian Ocean and equatorial eastern Pacific, especially the positive signals lasting in the tropical western Pacific in about one month ahead of the PHR events, and the key phase is week -3 and -1 ahead of the events. As to the South of the Yangtze River, the main regions are in equatorial areas, especially the central-southern Pacific, key phase is around week -3. And the signals affect Yangtze River valley events spread around, and are relatively in higher latitude, key phase is in week -4 and -3. Based on the selected OLR signals, regression equations are developed by using standard OLRs in these regions in respective leading time. The R2 of equations reach 0.958,0.731,0.933 respectively. Signals in tropics cover more information and get a higher climate frequency.