El Niño/Southern Oscillation (ENSO)
What is El Niño?
El Niño is a large scale oceanographic/meteorological phenomenon that develops in the Pacific Ocean, and is associated with extreme climatic variability i.e., devastating rains, winds, drought, etc. It is the migration from time to time of warm surface waters from the western equatorial Pacific Basin to the eastern equatorial Pacific region, along the coasts of Peru and Ecuador. This condition can prevail for more than a year thus adversely affecting the economy in both local and global scale.
El Niño translates from Spanish as the “Boy Child” or the “Little One”. It used to be considered a local event along the coast of Peru and Ecuador. The term was traditionally used by the Peruvian anchovy fishermen to describe the appearance of warm ocean current flowing the South American coast around Christmas time.
In normal condition, the prevailing southeasterly trade winds produce a surface current flowing toward the equator along the western South American coast. The waters leaving the coast are replaced by colder waters from below (upwelling), which is rich in phytoplankton, the food source of anchovy.
The warm current (El Niño) temporarily displaces nutrient-rich upwelling cold water resulting to heavy harvest of anchovies. The abundant catch, however, lasted for only a short period of time. What followed later was a sharp decline in the fish population resulting in lesser catch. At times, warming is exceptionally strong and ruins the anchovy harvest.
Characteristics of El Niño
•It occurs in the Pacific basin every 2 to 9 years;
•It usually starts during the Northern winter (December to February);
•Once stablished, it lasts until the first half of the following year, although at time , it stays longer (ex: 1939-1941 and 1989-1992 episodes);
•It exhibits phase-locking at annual cycles (El Niño and rainfall fluctuations with it tend to recur at the same time of the year); and
•It usually has a biennial cycle (El Niño events will often be preceded and/ or followed by La Niña).
What are the climatic indicators of El Niño phenomenon in the Philippines?
•Delayed onset of the rainy season
•Early termination of the rainy season
•Weak monsoon activity isolated heavy downpour with short duration
•Far tropical cyclone track
•Less number of tropical cyclones entering the PAR
What are the effects of ENSO in the Philippines?
In the Philippines, drought/dry spell events are associated with the occurrence of El Niño.
What provinces were already affected by drought/dry spell in the Philippines during the May to August 2015 rainfall assessment?
See maps and figures below.