Abstract
Abstract. The variations in oceanic and atmospheric modes on various timescales play important roles in generating global and regional climate variability. Many efforts have been devoted to identifying the relationships between the variations in climate modes and regional climate variability, but these have rarely explored the interconnections among these climate modes. Here we use climate indices to represent the variations in major climate modes and examine the harmonic relationship among the driving forces of climate modes using slow feature analysis (SFA) and wavelet analysis. We find that all of the significant peak periods of driving-force signals in the climate indices can be represented as harmonics of four base periods: 2.32, 3.90, 6.55, and 11.02 years. We infer that the period of 2.32 years is associated with the signal of the quasi-biennial oscillation (QBO). The periods of 3.90 and 6.55 years are linked to the intrinsic variability of the El Niño–Southern Oscillation (ENSO), and the period of 11.02 years arises from the sunspot cycle. Results suggest that the base periods and their harmonic oscillations related to QBO, ENSO, and solar activities act as key connections among the climatic modes with synchronous behaviors, highlighting the important roles of these three oscillations in the variability of the Earth's climate. Highlights. i. The harmonic relationship among the driving forces of climate modes was investigated by using slow feature analysis and wavelet analysis.ii. All of the significant peak periods of driving-force signals in climate indices can be represented as the harmonics of four base periods.iii. The four base periods related to QBO, ENSO, and solar activities act as the key linkages among different climatic modes with synchronous behaviors.
Highlights
We set the embedding dimension m to 11 for the Slow feature analysis (SFA) and extract each driving-force signal from six climate indices, which are denoted as Snino, Ssoi, Spdo, Samo, Snao, and Snaoi
In contrast to the quickly varying and lack-of-feature native climate index time series, the slowly varying signals appear to be a mixture of driving factors
Results show that each SFA-extracted signal involves significant peak periods at interannual to multidecadal timescales
Summary
The influences of large-scale climate modes (e.g., El Niño– Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), North Atlantic Oscillation (NAO), and the Atlantic Multidecadal Oscillation – AMO) on the variations of global to regional climate (e.g., temperature, rainfall, and atmospheric circulations) have been extensively examined (Bradley et al, 1987; Wu et al, 2003; McCabe et al, 2004; Kenyon and Hegerl, 2008; Steinman et al, 2015; Wang et al, 2016, 2017; Yang et al, 2016; R. Zhang et al, 2017; Xie et al, 2019). The NAO is active in the North Atlantic region, which is characterized by a large-scale seesaw in atmospheric mass between the subtropical high and the polar low (Li and Wang, 2003) It manifests as climate fluctuations at multiple timescales ranging from interannual to multidecadal variabilities (Jones et al, 1997; Li et al, 2013), affecting the climate within and around the North Atlantic Ocean basin and even the entire Northern Hemisphere We examine another observationally based monthly NAO index for the period 1850–2015 (hereafter referred to as NAOI), which is defined by the difference in the normalized sea level pressure (SLP) that is zonally averaged over the North Atlantic sector from 80◦ W to 30◦ E between 35 and 65◦ N (Li and Wang, 2003; http://ljp.gcess.cn/dct/page/65610, last access: 1 March 2020). The NAOI is calculated based on the HadSLP dataset with the reference period of 1961–1990
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
