Ch.4 Multifaceted Intraseasonal Modes in the east Asian-Western North Pacific Summer Monsoon Climate

Abstract

The East Asian?western North Pacific summer monsoon (EA-WNPSM) has multifaceted features involving complex dynamic interactions between local and large-scale circulations and nonlinear intraseasonal variability. These complexities cause difficulties in summer monsoon prediction, presenting a challenge in monsoon regions. In this chapter, we review dynamic and thermodynamic characteristics of distinguished intraseasonal modes in the EA-WNPSM, their irregularities in occurrences and patterns conducive to climate extremes, and asymmetric responses to El Nino? Southern Oscillation (ENSO). First, we briefly review the identification of the irregular four major intraseasonal modes. The four major modes are classified as the pre-Meiyu?Baiu, Changma?Meiyu, WNPSM, and monsoon gyre modes. The WNPSM and monsoon gyre modes occur preferentially in late summer and have the potential to trigger more frequent extreme rainfall in accordance with typhoon-related precipitation over the western North Pacific and the Korean Peninsula. Moreover, the asymmetric responses to ENSO provide sources of predictability that mainly originate from an interactive coupling over the Indian Ocean and western Pacific. Major predictors in terms of the modes have been obtained from persistent signals and trends of the ocean and land surface anomalous conditions reflected on a physical basis. Ultimately, these studies provide primary sources for prediction in the context of the intraseasonal variability of the EA-WNPSM, and the results have important implications for reducing extreme climate disasters in the EA-WNPSM region.