Abstract
Rainy season of central Vietnam is boreal autumn. In climatology, total rainfall during October-November accounts for about or more than 50% of annual rainfall. Heavy rainfall, which defined as daily rainfall exceeding or equal to 50 mm per day, also tends to occur during the rainy season.
The frequency of heavy rainfall during October-November is larger in La Niña year than that in El Niño year. The October-November total rainfall in central Vietnam and simultaneous Nino3.4 index shows negative correlation with statistical significance during the latter half of the 20-th century. However, statistical relationship between total rainfall and El Niño/La Niña events seems to be changed around the late 1970’s. Before 1976, total rainfall and heavy rainfall frequency have weak negative relationship to Nino 3.4 index. In addition, relationship between total rainfall and Nino 3.4 index is reversed in the period of 1928 through 1944.
