Effect Of El Niño-Southern Oscillation On Hurricanes


What is Niño-Southern Oscillation, or ENSO? Let us try to find the answer and the El Niño-Southern Oscillation effect on hurricanes in this article. Read on.


Niño-Southern Oscillation a climate pattern that takes place across the tropical Pacific Ocean every five years on average. The period for this event can however vary from three to seven years. Therefore it is also referred to as “quasi-periodic." ENSO is well-known for its relationship with floods, droughts and other weather disturbances in many regions of the world. The developing countries, which are particularly dependent upon agriculture and fishing, especially those bordering the Pacific Ocean, get the most affected.


Niño-Southern Oscillation is made up of an oceanic component, called El Niño. It is distinguished by warming or cooling of surface waters in the tropical eastern Pacific Ocean. The changes in surface pressure in the tropical western Pacific lead to another atmospheric component, known as the Southern Oscillation. The coupling of these two components gives rise to the El Niño-Southern Oscillation. When the warm oceanic phase is in process, surface pressures in the western Pacific are high, and when the cold phase is in effect, surface pressures in the western Pacific are low. Scientists are still studying the mechanisms causing these oscillations.


Commonly, El Niño-Southern Oscillation is called just "El Niño". El Niño is Spanish for "the boy" and "La Niña" is Spanish for "the girl." Let us look at the El Niño-Southern Oscillation effect on hurricanes.  Most of the hurricanes and cyclones develop on the side of the subtropical ridge closer to the equator. They then move poleward passing the ridge axis before re-curving into the main belt of the Westerlies.


When the subtropical ridge position moves due to El Nino, the preferred tropical cyclone tracks will also shift accordingly. West Japan and Korea witness much lesser September-November tropical cyclones during El Niño and neutral years. The break in the subtropical ridge during El Niño years lies near 130°E which favors the Japanese archipelago.


During El Niño years, the effect of El Niño-Southern Oscillation on hurricanes, in Guam is one-third of the long term average. Due to rise in vertical wind shear across the region during El Niño years, the tropical Atlantic ocean observes depressed activity. It is sent that during La Niña years, the formation of hurricanes along with the subtropical ridge position, moves westward across the western Pacific ocean, thus increasing the landfall danger to China.