Quasi-biennial oscillations extracted from the monthly NAO index and temperature records are phase-synchronized

Abstract. Using the extension of Monte Carlo Singular System Analysis (MC SSA), based on evaluating and testing the regularity of the dynamics of the SSA modes against the colored noise null hypothesis, we demonstrate detection of oscillatory modes with period of about 27 months in records of monthly average near-surface air temperature from several European locations, as well as in the monthly North Atlantic Oscillation index. According to their period, the detected modes can be attributed to the quasi-biennial oscillations (QBO). The QBO modes extracted from the temperature and from the NAO index underwent synchronization analysis and their phase synchronization has been confirmed with high statistical significance.