Fate of ENSO Phase on Upper Northern Thailand, a Case Study in Chiang Mai

This paper presents the impact of ENSO phase (El Niño and La Niña) on the variability of temperature and rainfall in Chiang Mai province, Upper Northern Thailand, and to identify the relation between ENSO index and temperature and rainfall. The study used data from four weather stations located at the altitude ranging from 320 to 1400 m a.s.l., covering the period of 1988 to 2011. We used two indexes, NIÑO3 (sea surface temperature based) and SOI (Southern Oscillation Index, atmospheric pressure based) to relate their impacts on temperature and rainfall several months in advance. The relationships of ENSO phases and the weather elements were higher by using SOI than NIÑO3. The corresponding results of correlation between 3-month running mean of SOI and monthly rainfall, Tmax and Tmin are found, especially during March to June in strong and medium ENSO years. The anomaly of Tmax related on SOI was shown higher than Tmin. Considering monthly rainfall, a significant decrease was found in May and June in only strong and medium ENSO events and the rainfall pattern differed significantly from the normal pattern. The variations of temperature and rainfall could be predicted by the SOI one to several months in advance and can be applied in other provinces in mountainous zone in Upper Northern Thailand.