Atlantic Oscillation indices in meridional distribution

The goal of this study was to define new oscillation indices of the Atlantic Ocean covering latitudes of both hemispheres, for the period from 1900 until 2014. Indices described sea level atmospheric pressure (SLP) oscillations between neighbouring cells of global atmospheric circulation (northern and southern Hadley, Ferrel and polar cells) and were calculated using two methods: conventional (based on SLP values in selected stations) and extreme values method (counted using maximum or minimum SLP from adequate areas). Twelve time series of new Atlantic Oscillation indices have been obtained—six conventional and six extreme, which have been presented in continuous form and through selection data by seasons: December–February (DJF), and June–August (JJA). The indices’ time series showed similarities in shared maxima and minima moments and long-lasting increasing tendency of five extreme and three conventional indices. There were strong correlations between oscillation indices describing variability in Hadley cells on both hemispheres (conventional 0.593–0.907, extreme 0.088–0.908). A strong correlation occurred between Southern Atlantic and Antarctic South Atlantic Extreme indices (0.668 to 0.979). Overall, stronger connections were found between extreme indices than the conventional ones, and most regularities were found in the Southern Hemisphere oscillations and wintertime indices (DJF for Northern and JJA for Southern Hemisphere). Power spectrum analysis showed major impact of 6- and 12-month periods, as well as less distinct significance of approximately 5.5-year-long interval and its multiples.