El Niño
Background - 2
El Niño
El Niño is a sea warming phenomenon
in the Pacific Ocean near the equator.
Trade wind is blowing in a certain direction at the equator. Due to the influence of trade wind, the ocean current flows the northwest in the Northern Hemisphere and southwest in the Southern Hemisphere, resulting in a warm current in the Western Pacific and a cold current in the Eastern Pacific.
In other words, the temperature of the sea in the western Pacific Ocean will be higher than that in the eastern Pacific Ocean.
As trade wind is weakening, warm seawater in the Western Pacific gradually moves east, and sea temperatures in the central and eastern Pacific oceans rise above sea temperatures in the average year.
Image from NOAA
Image from Climate.go.kr
When the sea surface temperature anomaly of the El Niño/La Niña monitoring area (equatorial Pacific Nino 3.4 area; 5°S~5°N, 170°W~120°W) is larger than 0.5 for more than
5 months, we consider the first month as El Niño/La Niña's start.
This Method is applied since 2016 Dec 23.
El Niño intensity is based on sea surface temperature (SST) anomalies
in a certain region of the equatorial Pacific.
When the SST departure is positively high, we say that El Niño is strong.