瞬变波动力强迫对初夏至盛夏东亚高空西风急流变化的影晌

利用NCEP／NCAR逐El再分析资料，探讨了瞬变波动力强迫作用对初夏至盛夏急流北跳和急流中心西移的影响。结果表明，瞬变波的动力强迫作用有利于急流北跳的发生，但不利于急流中心西移的发生。通过分析年际尺度上初夏至盛夏急流变化的早晚与瞬变波异常的关系发现，对于急流北跳发生的早晚，瞬变波异常的动力强迫作用为正反馈作用；对于中心西移发生的早晚，瞬变波异常的动力强迫作用则为负反馈作用。可见，瞬变波的动力强迫作用对初夏至盛夏急流变化及其发生早晚具有重要影响，但对急流北跳和急流中心西移的作用显著不同。

Effects of transient waves＇ dynamic forcing on variations of East Asian Subtropical Westerly Jet from early summer to midsummer

Effects of transient waves＇ dynamic forcing on the northward jump of jet and the westward movement of jet center from early summer to midsummer are studied by using NCEP/NCAR daily re- analysis data. The result shows that the transient waves＇ dynamic forcing is favorable to the northward jump of the jet, but not favorable to the westward movement of the jet center. Then the relationship be- tween the occurrence time of East Asian Subtropical Westerly Jet variations from early summer to mid- summer and anomalies of transient waves is further studied. The analysis revealed that the dynamic forc- ing of the transient anomalies has a positive feedback effect on the occurrence time of the jet＇s north- ward jump and a negative feedback effect on the occurrence time of the jet center＇s westward move- ment. So the transient waves＇ dynamic forcing has important influence on the variations and occurrence time of the East Asian Subtropical Westerly Jet from early summer to midsummer but exerts significant- ly different effects on the Jet＇s northward lump and its center＇s westward movement.