| Popis: |
The variations in oceanic and atmospheric modes on various timescales play important roles in generating regional and global climate variability. Many efforts have been devoted to identify the relationships between the variations in climate modes and regional climate variability, but rarely explored the interconnections among these climate modes. Here we use climate indices to represent the variations in major climate modes and we examine the harmonic relationship among the driving forces of climate modes by the combination of 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 the harmonics of four base periods: 2.32 yr, 3.90 yr, 6.55 yr and 11.02 yr. We infer that the period of 2.32 yr is associated with the signal of Quasi Biennial Oscillation (QBO). The periods of 3.90 yr and 6.55 yr are connected with the intrinsic variability of El Niño-Southern Oscillation (ENSO), and the period of 11.02 yr arises from the sunspot cycle. Results suggest that the base periods and their harmonic oscillations linked to QBO, ENSO and solar activities act as the key connections among the climatic modes with synchronous behaviors, highlighting the important roles of these three oscillations in the variability of current climate. |
