Interdecadal Fluctuation of Tripole Rainfall Pattern and Its Effect on Interannual and Subseasonal Variability

• Main Authors: Ying-Ting Chen, 陳英婷
• Other Authors: 許晃雄
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/28230827645218317372

碩士 === 國立臺灣大學 === 大氣科學研究所 === 97 === The tripole pattern is an important structure in East Asia during the northern summer. It is characterized by a zonally elongated and meridionally banded structure with signs changing alternatively from 0°N to 60°N along the East Asian coast. This study investigates the inter-decadal fluctuation of tripole rainfall pattern and its effect on inter-annual and sub-seasonal variability in 1958 to 2002. In 1980, the inter-decadal and inter-annual variations of tripole rainfall pattern changed from negative to positive phase. After 1980, there was more rainfall in northern and southern China, while there was less rainfall in central eastern China, Japan, and South Korea. The period and amplitude of inter-annual variation also increased after this year, so did the subseasonal variability. The spatial pattern of the change in interannual and subseasonal variance is similar to the tripole pattern. Both the positive SST and heat content increased in the northern Philippine Sea after 1980. It is suggested that the direct SST effect enhanced the cyclonic circulation and convergence in the lower troposphere in the tropical Western North Pacific, and in turn enhanced the tripole pattern through northward Rossby wave dispersion. It is hypothesized that the warmer Philippine Sea is able to provide an environment more favorable for the occurrence of convection activity in shorter time scale and therefore led to larger interannual and subseasonal variability.