A STUDY OFTHE INTERACTION BETWEEN THEASIAN SUMMER MONSOONAND EL NINO-SOUTHERN OSCILLATION

By contrast, the EA impact requires the prolonged ENSO that does not terminate in boreal spring because persistent anomalous convective heating in the vicinity of the Philippines from the preceding winter to late spring triggers a WES feedback regime in the Indian Ocean. Due to the frequent occurrence of the prolonged warm and cold events, the EA impact at the decay phase of ENSO becomes significant after the late 1970s. The ES impact at the growth phase of TBO-like ENSO brings about the strong ENSO-monsoon coupling prior to the late 1970s, while the occurrence of the prolonged ENSO after the late 1970s induces the EA impact on the monsoon at the decay phase of ENSO that is significant at the early stage of the monsoon season. Compared to the ES impact, the EA impact is indirect and not persistent until late summer. Furthermore, the monsoon after the late 1970s tends to experience both the ES and EA impacts of ENSO although the ES impact becomes less clear. We conclude that these features lead to the decline of the ENSO-monsoon relationship after the late 1970s.