This study objectively defined an extreme precipitation event(EPE)over southern China and investigated the associated typical circulation pattern on the intraseasonal time scale.The occurrence of the EPE resulted from...This study objectively defined an extreme precipitation event(EPE)over southern China and investigated the associated typical circulation pattern on the intraseasonal time scale.The occurrence of the EPE resulted from the joint operations of anomalous circulations over the subtropics and mid-high latitudes.During the EPE,simultaneous enhancements of the trough over the Bay of Bengal(BBT)and the Western Pacific subtropical high(WPSH)facilitated the abundant water vapor conditions over southern China,whereas the weakened East Asian major trough(EAT)led to a moderate cold air invasion to that region,producing a persistent convergence zone over southern China.Wave train pattern in North Atlantic and Europe may be viewed as precursory signals for the EPE over southern China,and it contributed to the Rossby wave propagation in association with the EPE.These wave packets propagated toward East Asia mainly along the North African-Asian subtropical westerly jet waveguide.Low-frequency disturbances along this waveguide contributed to the enhancement of the BBT and WPSH and the weakening of the EAT,constituting favorable circulation conditions for the EPE.展开更多
利用1979-2015年的NCEP/NCAR逐日再分析资料,分析了2009年冬季北半球平流层强爆发性增温事件(Stratospheric Sudden Worming,SSW)爆发期间的环流演变、动力特征以及增温事件爆发前对流层的前期信号。结果表明,平流层极夜急流于1月中旬...利用1979-2015年的NCEP/NCAR逐日再分析资料,分析了2009年冬季北半球平流层强爆发性增温事件(Stratospheric Sudden Worming,SSW)爆发期间的环流演变、动力特征以及增温事件爆发前对流层的前期信号。结果表明,平流层极夜急流于1月中旬开始快速减弱,同时,平流层极区温度快速上升,10 h Pa极夜急流核心纬度带(60°N-70°N)纬向平均纬向风于1月24日转变为东风,标志着此次强SSW的爆发。对行星波活动异常的诊断表明,从增温事件爆发前10天开始,中高纬度10 h Pa平流层2波分量快速增强,同时1波分量出现减少;Eliassen-Palm(EP)通量2波分量在SSW爆发前5天达到最强,表明此次SSW是典型的2波主导的极涡分裂型增温事件。此次强事件引起2009年冬季平均2波EP通量异常,此异常几乎是37年来最强的。对对流层500 h Pa环流的分析表明,增温事件爆发前,位于东北太平洋-北美大陆西部的正位势高度异常与气候态定常波的阿拉斯加高压脊呈同位相叠加,从而有效加强了对流层行星波2波向平流层中高纬地区的传播,成为指示此次增温事件爆发的最强的对流层前期信号。展开更多
基金supported by the National Basic Research Program of China(2012CB4172012009CB421401)+2 种基金the National Key Technologies R&D Program of China(2009BAC51B02)the National Natural Science Foundation of China(41375055)the China Meteorological Administration Special Public Welfare Research Fund(GYHY201106015)
文摘This study objectively defined an extreme precipitation event(EPE)over southern China and investigated the associated typical circulation pattern on the intraseasonal time scale.The occurrence of the EPE resulted from the joint operations of anomalous circulations over the subtropics and mid-high latitudes.During the EPE,simultaneous enhancements of the trough over the Bay of Bengal(BBT)and the Western Pacific subtropical high(WPSH)facilitated the abundant water vapor conditions over southern China,whereas the weakened East Asian major trough(EAT)led to a moderate cold air invasion to that region,producing a persistent convergence zone over southern China.Wave train pattern in North Atlantic and Europe may be viewed as precursory signals for the EPE over southern China,and it contributed to the Rossby wave propagation in association with the EPE.These wave packets propagated toward East Asia mainly along the North African-Asian subtropical westerly jet waveguide.Low-frequency disturbances along this waveguide contributed to the enhancement of the BBT and WPSH and the weakening of the EAT,constituting favorable circulation conditions for the EPE.
文摘利用1979-2015年的NCEP/NCAR逐日再分析资料,分析了2009年冬季北半球平流层强爆发性增温事件(Stratospheric Sudden Worming,SSW)爆发期间的环流演变、动力特征以及增温事件爆发前对流层的前期信号。结果表明,平流层极夜急流于1月中旬开始快速减弱,同时,平流层极区温度快速上升,10 h Pa极夜急流核心纬度带(60°N-70°N)纬向平均纬向风于1月24日转变为东风,标志着此次强SSW的爆发。对行星波活动异常的诊断表明,从增温事件爆发前10天开始,中高纬度10 h Pa平流层2波分量快速增强,同时1波分量出现减少;Eliassen-Palm(EP)通量2波分量在SSW爆发前5天达到最强,表明此次SSW是典型的2波主导的极涡分裂型增温事件。此次强事件引起2009年冬季平均2波EP通量异常,此异常几乎是37年来最强的。对对流层500 h Pa环流的分析表明,增温事件爆发前,位于东北太平洋-北美大陆西部的正位势高度异常与气候态定常波的阿拉斯加高压脊呈同位相叠加,从而有效加强了对流层行星波2波向平流层中高纬地区的传播,成为指示此次增温事件爆发的最强的对流层前期信号。
