Monsoon rainfall variations and teleconnections over South and East Asia

Seasonal summer monsoon (June-September) data for 120 stations over East Asia (China, Japan, Mongolia, Korea) varying from 1881 to 1998 are utilized to understand their interannual and climate characteristics, and to investigate their teleconnections with South Asian (in particular India's) monsoon rainfall. Contemporaneous relations on an interannual time-scale reveal that the rainfall variations over north China (southern Japan) are in-phase (out-of-phase) with South Asian rainfall. Based on the instrumental data available, regional rainfall anomaly time series for the 118-year period for the two coherent regions, over north China and southern Japan are prepared. All the three series (India, China, Japan) have been subjected to statistical tests. Results reveal that while there are year-to-year fluctuations, the Mann-Kendall rank statistic suggests no significant long-term trends. However, the application of Cramer's statistic to study the short-term climate variability depicts decadal variability with certain epochs of above and below normal rainfall over each region. The epochs tend to last for about three decades over India and China, and about five decades over Japan. The turning points for China follow those of India about a decade later. The relationships of South and East Asian monsoon rainfall exhibit secular variations. The inter-connections between the monsoon-related events (rainfall over South Asia, rainfall over East Asia, Northern Hemisphere circulation, tropical Pacific circulation) appear to strengthen (or weaken) around the same time, implying that the monsoon related events over geographically separated regions seem to get linked (or delinked) around the same time. Copyright (C) 2001 Royal Meteorological Society.