The coupled monsoon system

Abstract

The monsoons have received fervent attention for nearly 350 years. Early studies (e.g., Halley, 1686; Hadley, 1735) 1 were driven by both basic scienti®c curiosity and commercial necessity. The Indian Ocean and south Asia were areas of intense trading activity and the success of a trading venture depended on entering and exiting the south and east Asian regions during the proper phase of the monsoon annual cycle. Later research (e.g., Blandford, 1886, 1887; Walker, 1924, 1928) revolved mainly around societal and humanitarian issues as it had been noted that the livelihood and well being of these monsoon societies depends on the variations of the monsoon and the symbiotic relationship between agricultural practices and climate. Whereas the summer rains recur each year, they do so with sucient variability to create periods of relative drought and ¯ood throughout the region. Figure 1.1 shows examples of the interannual variability as long-term time series of rainfall for India and north Australia. Both time series possess di€erent means and each shows substantial interannual variability. The value of forecasting these varia-tions well in advance has immense value and can be used to optimize agricultural practices and water resource management, and to anticipate and mitigate disasters associated with monsoon variability. Forecasting monsoon variability was a major priority when systematic forecasting e€orts began over a century ago. It remains so today, as attempts are made to improve the quality of life in the monsoon regions and as society seeks avenues toward global sustainability. Perhaps the most important achievement in the last two decades has come from the identi®cation of the coupled ocean±atmosphere modes responsible for the El NinÄ o±Southern Oscillation (ENSO) phenomenon (see review by Wallace et al., 1998). This progress inspired the international Tropical Ocean±Global Atmosphere B. Wang (ed.), The Asian Monsoon. # Praxis. Springer Berlin Heidelberg 2006.