As a key component of the earth's climate system, the Asian monsoon (AM) affects the livelihood of more than 60% of the world population. The socio-economic infrastructure in the AM countries has been built, in large part, on the basis of the annual cycle of the monsoon. In particular, the water resources in these countries depend largely on the summer monsoon precipitation. On the other hand, many of the Asian countries are developing countries whose economies are fast growing yet considerably affected by anomalous monsoon climate and weather events. In particular, droughts and floods associated with the anomalous AM activities often cause severe property damage and loss of human life. It is well known that the AM is an extremely complex phenomenon that encompasses variabilities over a wide range of time scales from days to decades. Understanding the mechanisms that produce the observed variability in the AM region is a challenging scientific problem that must be addressed in order to advance the science of climate prediction, not only for the AM region but for the entire globe. Therefore, our ability to predict the AM variability is a critical requirement for the sustainable development of the AM region. Further, understanding and predicting monsoons is of great importance to the projections of future climate change due to the increase of the greenhouse gases concentration.