| ABSTRACT | The aim of the paper is to study the interannual-multidecadal variability of cyclonic and anticyclonic activity in the Mediterranean-Black Sea region associated with global processes in the ocean-atmosphere system: the North Atlantic Oscillation (NAO), El-Nino-Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO) and Atlantic Multidecadal Oscillation (AMO).
Global NCEP/NCAR reanalysis data sets on the 1000 hPa geopotential height in 1948 – 2013 were used to select cyclones and anticyclones and to calculate their main parameters: frequency, area, depth and intensity.
It was shown that in winter joint NAO and ENSO influence is responsible for up to 50% of the variance of the frequency of cyclones and anticyclones in the Black Sea region, while in the Mediterranean region it determines up to 25% and 30% of the depth and area variance of cyclones, accordingly. The positive NAO phase separately causes 47% of the decrease (increase) in the frequency of cyclones (anticyclones) in winter and 32% of the decrease of the frequency of anticyclones in summer in the Mediterranean-Black Sea region.
Taking into account our results of ENSO-events’ classification, in this paper it was shown that during the spring ENSO type and summer-autumn short type the frequency of anticyclones in the Mediterranean-Black Sea region increases, while the frequency of cyclones is characterized by the positive anomalies during the spring ENSO type and by the opposite sigh anomalies during the summer-autumn short type.
It was found that during the negative PDO phase winter cyclonic activity in the Black Sea region doubles in winter-spring. During the positive PDO phase frequency of the Black Sea anticyclones increases on 45% during autumn-winter, while in the Mediterranean it decreases in summer, autumn and winter.
It was confirmed that AMO strongly influences the character of cyclonic (anticyclonic) activity in the Mediterranean-Black Sea region in cold half-year. Positive AMO phase is characterized by cyclonic (anticyclonic) activity intensification (weakening), while the negative AMO phase is characterized by the opposite sign anomalies.
The schemes of the main trajectories of the Northern Hemisphere winter cyclones / anticyclones associated with AMO & PDO joint influence are presented for the two combinations: the first of them is the combination of negative AMO & PDO phases and the second one is the combination of the positive PDO & negative AMO phases. |