Autumn rainfall increasing trend in south central Vietnam and its association with changes in Vietnam’s East Sea surface temperature

Certain parts of Southeast Asia, such as central Vietnam, experience heavy rainfall in the boreal autumn from September to December (SOND). The 52-year SOND rainfall over Vietnam from 1961 to 2012 shows increasing trends over the south central region (SR). Along the central coastal regions and SR, SOND rainfall as well as heavy rainfall indices, such as the number of heavy rainfall days, have increased significantly since the late 1980s and early 1990s. In contrast, a decreasing trend is observed in stations located north of 17°N. Tropical cyclone-induced rainfall exhibits an increasing trend over the SR. The increasing trend of SOND rainfall is associated with the recent sea surface temperature (SST) warming after the late 1980s over the South Vietnam East Sea (SVES). Owing to the recent SST warming and grand La Niña-like pattern after the 1990s, the SVES surface temperature has increased by 0.8–1.2 °C over the period 1961–2012, leading to enhanced moisture flux convergence over the SR. Moreover, the SVES warming strengthens the anomalous northeasterly winds that affect the SR. Consequently, SR has become more prone to deep convection and heavy rainfall events