Changes in the Frequency of Phase Transitions of Different Types of El NIño Phenomena in Recent Decades

Estimates of changes in the frequency of transitions between different phases of El Niño processes over the past seven decades (1950–2019) have been obtained. Positive (El Niño phase) and negative (La Niña phase) surface temperature anomalies in the equatorial latitudes of the Pacific Ocean are associated with the strongest interannual variations in global surface air temperature. Significant differences in trends have been revealed for different types of El Niño and La Niña phenomena, characterized by surface temperature anomalies in the equatorial latitudes of the eastern (Niño3) and central (Niño4) regions of the Pacific Ocean. The tendencies of an increase in the frequency of occurrence of El Niño phases using the Niño4 index and neutral phases using the Niño3 index are noted. At the same time, for both types of El Niño, there is a tendency towards a decrease in the frequency of occurrence of La Niña phases. A significant contribution to the noted trends is associated with the regimes of a long (at least one year) manifestation of the corresponding phases.