Frequency of Winter Atmospheric Blockings in the Northern Hemisphere in Different Phases of El Niño, Pacific Decadal, and Atlantic Multidecadal Oscillations

Estimates of regional anomalies in the frequency of winter atmospheric blockings in the Northern Hemisphere, diagnosed using reanalysis data for 1979–2018, are presented in different phases of the El Niño, Pacific Decadal Oscillation (PDO), and Atlantic Multidecadal Oscillation (AMO). In particular, quantitative estimates are obtained of the regional frequency of winter blockings during El Niño of different types, characterized, in particular, by the Niño3 and Niño4 indices. During the neutral phase of El Niño phenomena in the positive phase of the PDO, a significant excess of the average frequency values of winter atmospheric blockings for a 40-year period over the Euro-Atlantic and Pacific sectors is noted. During the El Niño phase, a significant increase in the frequency of atmospheric blockings was noted in the negative phase of the PDO, as well as in the positive phase of the AMO, in particular, over the Pacific and Atlantic oceans. In the La Niña phase, using the Niño4 index, a significant increase in the frequency of atmospheric blocking in winter in the Ural Mountains region is revealed in the positive phase of the PDO and the negative phase of the AMO.