摘要
It is well known that Tropical cyclone （TC） activities over the Pacific are affected by E1 Nino events. In most studies El Nifio phenomena have been separated into east Pacific warming （EPW） and central Pacific wanning （CPW） based on the location of maximum SST anomaly. Since these two kinds of El Nino have different impacts on Pacific tropical cyclone activities, this study investigates different features of TC activities and the genesis potential index （GPI） during EPW years and CPW years. Four eontrib- nting factors, i.e., the low-level absolute vorticity, the relative humidity, the potential intensity and the vertical wind shear, are exam- ined to determine which factors are most important in causing the anomalous TC activities. Our results show that during EPW years in July-August （JA-0）, TC activities are more frequent with stronger intensity over the Western North Pacific （WNP） and Eastern North Pacific （ENP）. The maximum anomaly center of TC activities then drifts eastward siguifieantly in September-October （SO-0）. However, centers of anomalous TC activity barely change from JA-0 to SO-0 during CPW years. In January-February-March （JFM-1） of the decaying years of warming events, TC frequency and intensity both have positive anomaly over the South Pacific, The anoma- lies in EPW years have larger amplitude and wider spatial distribution than those in CPW years. These anomalous activities of TC are associated with GPI anomaly and the key factors affecting GPI anomaly for each ocean basin are quite different.
It is well known that Tropical cyclone(TC) activities over the Pacific are affected by El Nino events. In most studies El Nino phenomena have been separated into east Pacific warming(EPW) and central Pacific warming(CPW) based on the location of maximum SST anomaly. Since these two kinds of El Nino have different impacts on Pacific tropical cyclone activities, this study investigates different features of TC activities and the genesis potential index(GPI) during EPW years and CPW years. Four contrib- uting factors, i.e., the low-level absolute vorticity, the relative humidity, the potential intensity and the vertical wind shear, are exam- ined to determine which factors are most important in causing the anomalous TC activities. Our results show that during EPW years in July–August(JA0), TC activities are more frequent with stronger intensity over the Western North Pacific(WNP) and Eastern North Pacific(ENP). The maximum anomaly center of TC activities then drifts eastward significantly in September–October(SO0). However, centers of anomalous TC activity barely change from JA0 to SO0 during CPW years. In January–February–March(JFM1) of the decaying years of warming events, TC frequency and intensity both have positive anomaly over the South Pacific. The anoma- lies in EPW years have larger amplitude and wider spatial distribution than those in CPW years. These anomalous activities of TC are associated with GPI anomaly and the key factors affecting GPI anomaly for each ocean basin are quite different.
基金
supported by the National Basic Research Program of China (973 Program: 2012CB955604)
NSFC-Shangdong Joint Fund for Marine Science Research Centers (U1406401)
the CMA Program (GYHY200906008)
