Individual and Combined Impacts of Tropical Indo-Pacific SST Anomalies on Interannual Variation of the Indochina Peninsular Precipitation

Abstract

AbstractThis study documents interannual rainfall variations over the Indochina Peninsula (ICP) during the rainy season and individual and combined influences of tropical Indo-Pacific sea surface temperature (SST) anomalies. The rainfall variability is large along the west coast in May–June, along the west coast and over the eastern mountains in July–August, and along the central Vietnam coast in September–November. More rainfall in May–June, July–August, and October–November occurs in the La Niña decaying years, La Niña decaying years and/or El Niño developing years, and La Niña developing years, respectively. The May–June rainfall variation along the west coast is associated with equatorial central-eastern Pacific (EP), south Indian Ocean, and western North Pacific SST anomalies. The July–August rainfall variation along the west coast and over the eastern mountains is related to equatorial central Pacific and tropical southeastern Indian Ocean SST anomalies. The October–November rainfall variation along the central Vietnam coast is affected by EP and tropical western Indian Ocean SST anomalies. The EP and tropical western Indian Ocean SST influence is through anomalous Walker circulation. The south Indian Ocean SST influence is via cross-equatorial flows. The tropical southeastern Indian Ocean SST influence is via an anomalous cross-equatorial overturning circulation. The equatorial central Pacific and western North Pacific SST influence is via a Rossby wave–type response. The analysis illustrates the importance of combined effects of regional SST anomalies on the ICP precipitation variation in different stages of the rainy season. Numerical experiments with SST anomalies imposed in different regions confirm the combined effects of the Indo-Pacific SST anomalies on the ICP rainfall variation.