近32年泰国降水的主要变化趋势研究

Study of the Main Trend of Precipitation in Thailand over the Last 32 Years

基于泰国气象局提供的近32年(1981~2012)站点逐日降水观测资料,利用线性趋势和集合经验模态分解(Ensemble empirical mode decomposition, EEMD)等分析方法,本文重点研究了泰国及其五个地理分区内各等级降水量与降水日数出现正异常(第95百分位及以上)的站点比例变化,并深入分析了泰国逐年降水量与暴雨级别以上持续性和非持续性降水量相对贡献的变化。主要结论如下:(1)泰国东部和南部地区是其降水最强的区域,而泰国北部地区降水相对最弱,在研究的32年时段内,泰国境内有87%的站点出现了逐年降水增加的趋势(共有22个站通过了95%置信水平的显著性检验),其中泰国南部是增加最快的区域,而泰国东部地区则是出现降水增加趋势最少的地区。位于泰国湾沿岸的曼谷站和洛坤站是整个泰国境内逐年降水增加最快的站点。(2)泰国北部地区的逐年降水量、逐年降水日数与平均降水强度出现正异常的站点比例显著增加,表明极端降水的影响范围在扩大,而泰国南部地区仅大暴雨级别以上的极端降水出现了范围扩大的趋势。(3)暴雨级别以上的降水在泰国不同地区存在着显著差异,其中泰国北部、东北部和中部地区,非持续性降水占主导地位,而在泰国东部和南部地区,持续性与非持续性降水的贡献相当。暴雨级别以上持续性降水出现正异常的站点比例在泰国北部和南部地区有显著的增加趋势,表明这些地区受稳定系统影响所发生强降水的范围有着显著的扩大趋势。

On the basis of 32-year daily precipitation observation data from Thailand’s meteorological department during1981–2012, using linear trend and EEMD(ensemble empirical mode decomposition), this study focused on the changes in the proportion of stations with abnormally high(95th percentile and above) 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 the relative contribution of annual persistent and nonpersistent precipitation to annual precipitation above heavy rain level. The main conclusions are as follows:(1) Annual precipitation is the strongest in eastern and southern Thailand and the weakest in northern Thailand. Additionally, during the 32-year study period, it shows an increasing trend at 87% of the stations(with 22 stations reaching the 90% confidence level), showing the fastest increase in South Thailand and the slowest increase in eastern Thailand. In Thailand, annual precipitation at the Bangkok and Nakhon Si Thammarat stations on the coast of the Gulf of Thailand shows the most significant increasing trend.(2) The proportion of stations with abnormally high annual precipitation, annual precipitation days, and mean precipitation intensity increase significantly in North Thailand, which indicates that the range of extreme precipitation is expanding,while in southern Thailand, only the range of extreme precipitation for precipitation above storm rain level increases significantly.(3) In Thailand, precipitation above heavy rain level varies significantly in different regions. In North,Northeast, and central Thailand, precipitation-heavy is more of a nonpersistent form, while in East and South Thailand,two forms(nonpersistent and persistent) of precipitation are balanced. The proportion of stations with abnormally high persistent precipitation above heavy rain level 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.