副热带季风边缘区降水变化及其影响因素

Precipitation variation characteristics and influencing factors in the subtropical monsoon marginal zone

选取英国东英吉利大学气候研究中心降水月值数据计算出季风区,得出季风边界的年际变化,探究季风边缘区降水强度与季风强度和季风区面积的关系.计算了太平洋年代际振荡(PDO)指数、厄尔尼诺-南方涛动指数及大气环流场,探讨了副热带季风边缘区降水变化的影响因素.结果表明,季风边界线摆动幅度较小的区域降水有明显的增加趋势,而边界线摆动幅度较大的区域降水均呈减少的趋势.近50 a来PDO主要处于暖位相阶段,北美西岸海表面温度异常暖,北太平洋海平面气压异常低,使得季风环流减弱,环北太平洋的副热带季风边缘区降水减少.东亚夏季风边缘区有较明显的变干趋势,其中以内蒙古高原东部和黄土高原的变干趋势最明显,分布于青藏高原的夏季风边缘区有明显的变湿趋势;北美夏季风边缘区纬向的降水差异较为明显,东南部和西北部降水减少,中部呈现降水增多的趋势.

We selected the monthly global gridded precipitation data from the climatic research unit of University of East Anglia to depict the subtropical monsoon domains for an investigation of the relationship between the monsoon marginal zone rainfall,monsoon intensity and monsoon area.We also analyzed the combined effect of Pacific decadal oscillation(PDO),El Ni?o-Southern Oscillation and atmospheric circulation on the subtropical monsoon marginal zone precipitation variation.The results showed that the precipitation in the area where the monsoon boundary line with small amplitude of oscillation had a significant an increasing trend,while the precipitation in the area where the boundary line swung to a large extent had a decreasing trend.Since the PDO was mainly in the warm phase in the past 50 years,the sea surface temperature in the western coast of North America was unusually warm,and the sea level pressure in the North Pacific was abnormally low,which weakened the monsoon circulation and suppressed the precipitation in the subtropical monsoon marginal region of the North Pacific Ocean.The East Asian summer monsoon marginal zone had an obvious drying tendency,of which the dryness trend was most obvious in the eastern Inner Mongolia Plateau and the Loess Plateau,while the wet conditions were obvious in the Qinghai-Tibet Plateau.The difference of boundary zone precipitation was significant,with precipitation decreasing in the southeast and northwest,while increasing in the central part.This study could help us understand the variability and regional differences of subtropical monsoon marginal zone precipitation,and to assess the sensitive response of monsoon marginal regions to global monsoon changes.