Nino 3.4 region
Also called: Oceanic Nino Index · Topic: Atmospheric Pressure, Winds and General Circulation · NCERT: Beyond NCERT
Meaning
The Nino 3.4 region is a box in the central equatorial Pacific, from 5°N to 5°S and from 120°W to 170°W. Scientists watch how much warmer or cooler its surface water is than normal. NOAA (the US weather and ocean agency) uses this to work out its Oceanic Nino Index. It declares an El Nino when the three-month average is 0.5 °C or more above normal, and a La Nina when it is 0.5 °C or more below. This must last over several overlapping three-month seasons. Australia and IMD use their own rules.
Example
In 2023–24, sea temperatures in the Nino 3.4 box stayed well above the threshold, and a strong El Nino was declared.
Don't confuse with
- Oceanic Nino Index: this is the number calculated from the region's temperatures. The Nino 3.4 region is the area of ocean where they are measured.
- Southern Oscillation Index: it is based on air pressure (Tahiti minus Darwin), not sea temperature.