The rainfall variation in central Vietnam

• Main Authors: Dinh Duc, 丁德朵
• Other Authors: Ming-Cheng Yen
• Format: Others
• Language: en_US
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/67055460662228534183

碩士 === 國立中央大學 === 大氣物理研究所 === 98 === The weather of Vietnam, a subtropical country located along the east coast of the Indochina Peninsula on the north-western Pacific Ocean, is greatly affected by both East Asian winter and summer monsoon systems beside the tropical activities occurred during the seasonal transition period. However, the most severe flooding events frequently appear in the central Vietnam (120N-190N) during fall rainy season. The 2007 disastrous damages in this region caused by sequential heavy rainfall had been attracted much attention. Thus, the major purpose of this study is to investigate the possible causes of heavy rainfall events in central Vietnam during Oct–Nov 2007 from climate perspective, especially the interannual variation effect of ENSO. By using EOF analysis of 163 daily rainfall station data in Vietnam, two significant rainfall regimes were identified: the fall rainfall regime (Oct - Nov) in central Vietnam and summer rainfall regime (May - Oct) in the northern and southern regions of this country. The fall rainfall regime, the most important component in 2007, explained 48.31% of the total variation. It is interesting that a close relationship between the Oct-Nov precipitation in central Vietnam and ENSO was distinctly exhibited. In general, heavy rainfall would occur in this region during cold phase (La Nina), while the appearance of dry conditions is corresponded to warm phase (El Nino). Over the positive (negative) SST anomaly at northwestern Pacific Ocean, an anomalous cyclonic circulation adjoined to the coast of central Vietnam together with a positive convergent anomaly and strong water vapor transport from the warm sea surface during La Nina events played an important role for inducing heavy rainfall in central Vietnam during Oct-Nov, while the opposite situation in El Nino years were responsible for the dry conditions in central Vietnam.