华南地区春雨进程的气候特点及其气候季节内振荡

EVOLVEMENT OF CLIMATIC SPRING PRECIPITATION OVER SOUTHERN CHINA AND ITS CLIMATOLOGICAL INTRASEASONAL OSCILLATION

利用观测和再分析资料,从气候学的角度研究春雨在华南各地的开始、推进和气候季节内振荡的特点,以及相应的大气环流特征。分析表明:华南各地雨量随时间振荡增加,雨季进程较为相近,第12—24候各地先后进入雨季,但存在差异。雨季最先在雨量大值中心开始,然后向周边推进;第20候后各地逐步进入春雨的盛期。华南春雨CISO不仅在统计上是显著的,也对应着协调的大气环流配置;其振荡过程的峰(谷)值分别对应雨量的显著增加(减少),调制华南春季降水的演变,3月下半月和4月上旬后期到中旬前期的雨量增长正是CISO调节的结果。当中国东部对流层低层为气旋环流、高层为反气旋环流时,华南受低层辐合、高层辐散这种具有斜压结构的环流配置影响,上升运动发展,CISO处于湿位相。

Based on observations and reanalysis data, the characteristics of the evolvement of climatic spring precipitation over Southern China （SPSC） and the climatological lntraseasonal oscillation （CISO） as well as the corresponding atmospheric circulation features are studied. Results show that SPSC increases in an oscillatory way. Although the evolvement of SPSC is similar in different regions, there are also differences. In different regions of Southern China, the onset dates of the rainy season are from the 20th to 24th pentad and the peak dates are reached after the 20th pentad. CISO is an important component of SPSC, which is not only statistically significant, but also accompanies a dynamically coherent structure. The peak wet/dry phase of each CISO cycle corresponds to a significant rainfall increasing/decreasing period, and modulates the evolvement of SPSC. The rainfall growth in the second half of March and mid-April is the result of the modulation. The CISO wet/dry phase is accompanied by low-level convergent （upper-level divergent） cyclonic （anti-cyclonic） circulation, which favors ascending motions to develop over Southern China.