NAO对青藏高原中东部夏季降水双极振荡模态影响的时间尺度厘定

Statistical Diagnosis of the Relationship between NAO and Dipole Oscillation of Summer Precipitation over Qinghai-Xizang Plateau in Multi-time Scales

通过对1961 2010年青藏高原中东部66个台站夏季降水的EOF分析,进一步证实在现代气候背景下南北双极振荡模态是夏季青藏高原最主要的降水空间结构,并表现出较强的稳定性,相关分析表明该模态与夏季北大西洋涛动(NAO)存在稳定密切的联系。集合经验模态分解(EEMD)能够根据NAO和青藏高原降水双极振荡模态时间系数序列自身的特点而把原序列中不同时间尺度的信息分离出来,夏季NAO与青藏高原降水双极振荡模态之间最显著的联系主要发生在以准3~4年为周期的年际信号里,因此,以NAO为主的北大西洋大气活动(而非该地区的海温变化)可能是驱动青藏高原夏季降水南北双极振荡模态形成的最主要原因之一。

The spatiotemporal characteristics of summer precipitation over the Qinghai-Xizang Plateau( QXP)during 1961 2010 are investigated based on a developed daily precipitation dataset at 66 meteorological stations. According to the empirical orthogonal functions( EOF) analyses,it is confirmed that the reverse relationship between the northeastern and southeastern QXP is the main and stable spatial pattern of summer precipitation over the QXP in modern times which is defined as the Dipole Oscillation. And such Dipole Oscillation is mainly impacted by the summer North Atlantic Oscillation( NAO). The results showthat ensemble empirical mode decomposition( EEM D) can extract the potential signals of multi-time scales effectively from the NAO index and time series of the Dipole Oscillation according to their own typical features. The correlation analysis reveals the most important correlation between NAO and Dipole Oscillation occurs at the interannual time scale with a spectral peak in 3 ~ 4 years. Further analysis implies the atmosphere activity represented by NAO rather than sea surface temperature over Atlantic should be considered as the main possible driver of the Dipole Oscillation.