THE CHARACTERISTICS OF ATMOSPHERICAL CIRCULATION AND STATUS OF RAINFALL DEFICIT IN VIET NAM DURING 2014-2016 EL NINO EVENT

Abstract

Analysis of the relationship between atmospheric circulation characteristics and rainfall deficit in Viet Nam during the 2014-2016 El Nino was based on the NCEP/NCAR re-analysis dataset and 54 observed rainfall stations in Viet Nam. The results show that during the event, the main characteristics of atmospheric circulation over East Asia-West Pacific were found: Weakening of the Western Pacific subtropical high; southward and eastward shift of the Equatorial Low-pressure trough; Decreasing of pressure over the North East Pacific and eastern wind, Eastward moisture transformation, outgoing longwave radiation over the eastern part of the tropical equatorial Pacific; Increasing of pressure over the West Pacific and outgoing longwave radiation over Viet Nam and adjacent regions. The frequency of monthly rainfall deficit was around 50% in North West, North East, North Delta, 60% in North Central, South Central and 75.9% in Central Highlands, 73.0% on South Delta. The ratio of meteorological stations with rainfall deficit in the event was 25% in North West, 28.6 on North East, 37.5 in North Delta, 88.9% in South Central and 100% in North Central, Central Highlands, South Delta. In general, rainfall deficit gradually decreased from South to North climate zones. In particular, the most deficient rainfall in this event reached 1887.6 mm at Phu Quoc meteorological station.