Institute of Atmospheric Physics， Chinese Academy of Sciences
Based on 32-yr daily precipitation observation data from Thailand"s meteorological department during 1981-2012, by using linear trend and ensemble empirical mode decomposition (EEMD), this study focused on the changes in the proportion of stations with abnormally high (95 percentiles and above) of precipitation and precipitation days in multiple grades in Thailand as a whole and its five geographical regions, and further analyzed the annual precipitation and the variation trend of relative contribution of annual persistent and non-persistent precipitation-heavy to annual precipitation-heavy. The main conclusions are as follows : 1) Annual precipitation is strongest in East and South Thailand, while weakest in North Thailand. And during the study period of 32 years, it shows an increasing trend on 87% of stations (with 22 stations reach the significance level of 90% T test), showing the fastest increase in South Thailand and the least increase in East Thailand. In Thailand, annual precipitation in Bangkok station and Nakhon Si Thammarat station on the Coast of the Gulf of Thailand shows the most significant increasing trend. 2) The proportion of stations with abnormally high of annual precipitation, annual precipitation days and mean precipitation intensity increase significantly in North Thailand, which indicates the range of extreme precipitation is expanding, while in South Thailand, only the range of extreme precipitation for precipitation-storm increases significantly. 3) In Thailand, precipitation-heavy varies significantly in different regions. In North, Northeast and Central Thailand, precipitation-heavy is more of non-persistent form, while in East and South Thailand, two forms (non-persistent and persistent) of precipitation are balanced. The proportion of stations with abnormally high of persistent precipitation-heavy has a significant expansion trend in North and South Thailand, which indicates that the range of heavy precipitation under the influence of the stable system has a significant expansion trend.