冬季西太平洋暖池与华南降水关系的年代际变化

Interdecadal variation of relationship between the western Pacific warm pool and precipitation over South China in winter

利用1951—2010年全国台站冬季降水观测资料、Hadley环流中心逐月海表温度资料以及NCEP/NCAR再分析月平均资料,探讨了西太平洋暖池与我国华南地区冬季降水的关系。结果表明,西太平洋暖池与我国华南冬季降水的年际关系在1972年发生了明显的年代际转折,20世纪70年代前两者弱的负相关未通过信度检验,而70年代后两者相关系数达到-0.5^-0.6。回归分析显示,70年代前,暖池对产生华南冬季降水的水汽条件以及动力条件等的影响不显著,因此其与华南冬季降水的关系不明显。70年代后,暖池偏暖时,在菲律宾海区域激发出一个显著的气旋性环流,该环流西北侧的偏北风不利于南海地区水汽向我国华南地区输送,华南地区水汽辐散增强,而且南支槽地区对流减弱,南支扰动不活跃且扰动不能向下游地区传播,华南地区扰动活动减弱,此外暖池偏暖使北半球经向环流显著增强,且下沉支位于我国华南地区,加强了华南地区的下沉运动,因而华南地区冬季降水显著偏少;暖池偏冷时,情况相反。

Based on the observed station precipitation data over China in winter,the monthly Hadley Center Global Sea Ice and Sea Surface Temperature（ Had ISST） and the monthly reanalysis data provided by National Centers for Environmental Prediction-National Center for Atmospheric Research（ NCEP / NCAR）from 1951 to 2010,the relationship between the western Pacific warm pool（ WPWP） and winter precipitation over South China（ SC） has been studied. The results show that the correlation between WPWP and winter precipitation over SC has obvious interdecadal transition in 1972. Before the 1970 s,the negative correlation between them is weak and has not passed significance test. But the correlation between them has reached- 0. 5—- 0. 6 after the 1970 s. By the regression analysis,it is found that,before the 1970 s,the effect of WPWP on water vapor and dynamic conditions that affect winter rainfall over SC is not significant,so its relation with winter rainfall over SC is not obvious. After the 1970 s,when WPWP SST is warmer,an obvious cyclonic circulation has been aroused in the Philippine Sea area. The northerly wind over the northwest side of the cyclonic circulation is not favor of water vapor from South China Sea trans-ported to SC,so the water vapor divergence over SC increases. The convection and perturbation over the southern branch trough region weaken significantly and the perturbation can not spread to the downstream region,which causes the weakened perturbation over SC. In addition,the warming of WPWP leads to remarkable increase of meridional circulation in the Northern Hemisphere,and the sinking branch is located in SC region,which strengthens the sinking movement over SC,so it results in the decreased rainfall over SC in winter,and vice versa.