ISOS OF TBB OVER SCS AND VICINITY AS WELLAS ITS RELATIONSHIP WITH ENSO

Using the TBB data from 1980 to 1997, the intra seasonal oscillations (ISOs) over the South China Sea (SCS) and surrounding regions were diagnosed with the wavelet analysis. The results show that the ISOs features of TBB over SCS are similar to that over the east of the Philippine, with single peak in summer, but different to that over the Bay of Bagel, with dual peaks in May and November. The periodic structure of the ISOs over SCS is complex and there are two major periods of 50-70 days with peak at 53.8day (ISO1) and 13-36 days with peak at 32-day (ISO2). The variance of ISO2 is about three times of that of ISO1. Because of the significant positive relationship of ISO1 between SCS and surrounding regions, the inter annual variations of ISO1 has large-scale characteristics, but that of ISO2 is a local phenomenon. The migrations of ISOs to the SCS take on multi directions. ISO1 migrates eastward and ISO2 westward and all migrate northward. It indicates the ISOs over SCS can be influenced by the oscillations coming from not only equatorial region, but also west Pacific and the Bay of Bengal. And the local convections generated over SCS also impact the ISOs. So the ISOs of convection over SCS become complex. The statistic results show that the strong (weakening) annual variation of ISO1 is often linked to the cold (warm) phase of ENSO. It is found that ENSO is related with ISO1 more closely than with ISO2. In the warm phase of ENSO, the convections over SCS are weakened. It results in the high TBB values and the weakening ISO1. It suggests that the anomalous tropical atmosphere circulation (for example, the subtropical high over the western Pacific) induced by ENSO can modulate the ISO1 of TBB over SCS.