Os

0.1 0.2 0.3 0.4 Frequency (cycles/year)

Figure 5.32. Singular Spectrum Analysis (SSA) results - periodograms of the reconstructed courses of: a, b, and c - occurrence frequency of atmospheric circulation macrotypes W, C, and E according to the Vangengeim-Girs typology; d - zonal index; e - Wolfs sunspot numbers; f - mean water temperature in a 0-200 m-deep layer along a profile of the Barents Sea.

Shorter oscillation periods (2-3 years) observed in T. series from particular stations may be connected with quasi-biennial change in the circulation of stratospheric winds. Somewhat longer periods (4-5 years), observed exclusively in the north-western part of the Canadian Arctic, may be a result of the El Nino-Southern Oscillation (ENSO). A periodicity similar to the basic cycle of solar activity (ca. 11-years) occurs exclusively in Alaska and surrounding seas.

However, it is worth observing that the periodicities observed in the characterisations of circulation analysed (64.1, 31.9, 25.6, 16.0, 12.8, and 9.1 years) are the higher harmonics of the long-term oscillations (256.4 years) detected in the series of the number of sunspots from 1749-1990 (Figure

5.32). It is not impossible that changes in atmospheric circulation may be caused by solar activity. According to Charvátová and Strestik (1991, 1992, 1995), variability in solar activity, in turn, depends on solar inertial motion, which is characterised by oscillations whose dominant period is 178.4 years. Many higher harmonics of this cycle (ca. 80-90; 60; 45; 35; ...; 12.8;...; 11.1;...; 10.0; ...; 7.8 years;...), which correspond to the synodic and sidereal periods of planets are also significant (Charvátová & StreStík 1993). As can be seen, some of these cycles approximate the oscillation periods in the series of sunspots detected, in the circulation characterisations analysed, and in the series of T.

Research conducted during the 1980s demonstrated that it is not impossible that all the fluctuations observed in weather and climate are merely the product of the non-linear behaviour of the atmosphere (Burroughs 1992).

There undoubtedly exists in the Arctic a significant similarity between the cyclicities of atmospheric circulation and T. It is difficult to determine whether the periodicity detected in the atmosphere is caused by extra-terrestrial factors or whether it results from the non-linear behaviour of the atmosphere.

Was this article helpful?

0 0

Post a comment