An analysis of El Niño, requires consideration of the variables that are affected by the event;

One of the variables that best evidence the changes caused by El Niño is the Southern Oscillation Index (Southern Oscillation Index – SOI) expressing the standardized pressure difference between Darwin and Tahiti in the Pacific Ocean, expressing changes in the atmospheric system are reflected in the dynamics of the anticyclone of the South (AS), with its increase, the trade winds are strengthened (VA
Another variable to consider and express the frequency, is the Pacific Decadal Oscillation (PDO), which is a persistent pattern of spatial climate variability of about 50, which covers the entire tropical Pacific Ocean, defined as a harmonic oscillation

As seen, South Eastern Pacific is the setting for patterns of variability such as seasonality (summer and winter), the inter annuity (El Niño - La Niña), periodicity (PDO) and secularity (PSV).
Seasonality is a pattern of short-term variability that takes place annually associated with the motion of the earth around the sun.

The ENSO (El Niño Southern Oscillation), affect the seasonality doing the warmer and longer summers and less cold and less severe winters when trying to El Niño, meanwhile, in the case of La Niña, the effect
The PDO (Pacific Decadal Oscillation), periodicity of about 50 years with a positive phase and a negative phase of approximately 20 and 30 years, respectively.

The Secular Variability of the Pacific (Pacific Secular Variability – PSV), is based on long-term oscillations of greater than about 100, with high and low phase variation.

Then, El Niño is affected by two processes larger scale corresponding to the PDO and PSV so that in its manifestation can have impacts on the environment and ecosystem totally different in each case, as will be subjected to thermal regimes and intensity

For example, if an El Niño event occurs at a time when PSV match high (high variability) with a positive PDO (warm moment), the manifestation of the event is high with extreme effects on the ecosystem.

Against this background, one can conclude that the years between 1975 and 2000 coincided with periods of high variability (PSV) and a positive phase of the PDO.
Currently (2014) we are in a negative phase of the PDO and the second half of the PSV;

Extreme El Niño events could occur at the end of this cold phase and begin the warm phase of the PDO;

Finally, with respect to El Niño current development, is responding to seasonal variability fading with it. His expression does not exceed the moderate category and is expected to maintain this rating, as reported very aptly ENFEN Scientific Committee. To date, missing six months for 2015, it is not possible to venture forecasts in relation to the continuity of this event and even less in their intensity and duration. Follow ENFEN results would be more advisable.

By: * Marco Espino
Instituto del Mar del Peru, IMARPE
Photo: Pacific Decadal Oscillation (OPD) and Variability Secular Pacific (PSV) and trends