The sub seasonal activity in the Indo-Pacific region is dominated by the Madden-Julian Oscillation (MJO), which can be defined as a 30-50-day oscillation that moves eastward from at least the Indian Ocean to the Central Pacific Ocean. This intraseasonal oscillation organizes convection on a regional scale and, by modulation of the strength and position of the main tropical heat source, is thought to strongly influence large-scale climatic phenomena, such as the Asian Summer Monsoon (ASM) and the El Nina Southern Oscillation (ENSO). The aim of this project is to identify the mechanisms in this suggested relationship with a focus on the boreal summer season. To that end, we will first analyse the evolution of the coupled Indo-Pacific system during the summer of 2002, which provides an unprecedented example illustrating the influence of the MJO on the ASM and ENSO. The analysis of recent high-quality observational data sets and various sensitivity experiments with forced ocean and atmosphere General Circulation Models (Gems) will allow us to identify the major intraseasonal patterns and build hypotheses on the mechanisms that could link these patterns with the ASM and ENSO. In the second phase, high-resolution coupled Gems will be used to confirm the previous suggested mechanisms and generalize the 2002 case study to various other large-scale Indo-Pacific conditions. An improved understanding of the influence of the intraseasonal activity in the Indo-Pacific sector will have implications in terms of predictability. Indeed, confirmation of the role of intraseasonal forcing on the development of ENSO and ASM activity may imply a limit to long-term predictability of these large-scale phenomena.
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