【中文介绍】

  青藏高原作为世界“第三极”，也被称为“亚洲水塔”，是亚洲主要大江大河的发源地。夏季降水作为高原陆地水储量的重要补充水源，其空间格局的变化对区域气候和生态系统的平衡有重要影响。已往研究指出青藏高原夏季降水偶极子模态与北大西洋涛动（NAO）紧密相关，夏季NAO可以通过激发沿欧亚大陆的波列传播，影响青藏高原南北地区的水汽输送，进而影响高原夏季降水的空间格局。然而，青藏高原夏季降水偶极子模态与NAO的关系是否稳定，这仍然值得关注。

  基于实测数据、多源再分析资料以及数值模式，重点分析了夏季NAO与青藏高原降水偶极子模态的不稳定关系及其可能机制。结果指出，自20世纪90年代末以来，夏季NAO与青藏高原降水偶极子模态的联系在减弱。沿欧亚大陆不对称波传播结构引起的区域大气环流的变化是造成这种联系减弱的主要原因。进一步分析表明，大西洋多年代际振荡（AMO）可以调制夏季NAO和青藏高原降水偶极子模态的联系。在AMO的暖位相，青藏高原东部净水汽输入加强，导致东部地区整体降水偏多，不利于降水偶极子模态的形成。此外，基于GFDL AM2.1模式的海温敏感性试验结果进一步证明，AMO位相转变对夏季NAO与青藏高原东部降水偶极子模态之间的不稳定关系有重要贡献。该研究揭示的青藏高原夏季降水偶极子模态与NAO关系的不稳定性及物理机制有助于深入理解青藏高原夏季降水变化的成因。

  【英文介绍】

   Substantial progress has been made in understanding the relationship between summer precipitation in the Tibetan Plateau (TP) and North Atlantic Oscillation (NAO), but impacts of the summer NAO on precipitation spatial pattern remain controversial. Using the long-term observational and reanalysis datasets, we have identified the intimate relationship between summer NAO and TP precipitation dipole pattern has been weakened since the late 1990s. Changes in regional atmospheric circulation induced by the asymmetrical wave propagation structure along the Eurasian continent are responsible for this weakened linkage. Further analyses revealed that the wave propagation anomalies are mainly induced by interdecadal change of summer NAO, which is attributed to the Atlantic multidecadal oscillation (AMO) variations. Moreover, the model simulations derived from the Geophysical Fluid Dynamics Laboratory (GFDL AM2.1) provide direct evidence to demonstrate that the AMO phase transition contributes to the unstable relationship between the summer NAO and precipitation dipole pattern in the eastern TP.

  【关键图表】

  【引用格式】       

  Liu Y., Chen H. P., Hu X. Y. (2021). The unstable relationship between the precipitation dipole pattern on the Tibetan Plateau and summer NAO. Geophysical Research Letters, 48, e2020GL091941.