What is ENSO in simple terms?
What is ENSO in simple terms?
“ENSO” refers to the El Niño/Southern Oscillation, the interaction between the atmosphere and ocean in the tropical Pacific that results in a somewhat periodic variation between between below-normal and above-normal sea surface temperatures and dry and wet conditions over the course of a few years.
How do you read an ENSO index?
Prolonged periods of negative (positive) SOI values coincide with abnormally warm (cold) ocean waters across the eastern tropical Pacific typical of El Niño (La Niña) episodes….Southern Oscillation Index (SOI)
| Date | SOI |
|---|---|
| 195103 | -0.1 |
| 195104 | -0.3 |
| 195105 | -0.7 |
| 195106 | +0.2 |
What is the ENSO 3.4 index?
The Niño 3.4 index typically uses a 5-month running mean, and El Niño or La Niña events are defined when the Niño 3.4 SSTs exceed +/- 0.4C for a period of six months or more. The TNI is defined to be the difference in normalized SST anomalies between the Niño 1+2 and Niño 4 regions.
What does ENSO measure?
El Niño and the Southern Oscillation, also known as ENSO is a periodic fluctuation in sea surface temperature (El Niño) and the air pressure of the overlying atmosphere (Southern Oscillation) across the equatorial Pacific Ocean. variation in sea level barometric pressure. as measured by a barometer.)
Why do the trade winds weaken?
The air-sea interaction that occur during an El Niño event feed off of each other. As the pressure falls in the east and rises in the west, the surface pressure gradient is reduced and the trade winds weaken.
What is negative Southern Oscillation?
The negative phase of the Southern Oscillation occurs during El Niño episodes, and refers to the situation when abnormally high air pressure covers Indonesia and the western tropical Pacific and abnormally low air pressure covers the eastern tropical Pacific.
What is NINO 34?
Equatorial Pacific Sea Surface Temperatures (SST) This standard of measure is known as the Oceanic Niño Index (ONI). The most commonly used region is the Niño 3.4 region, and the most commonly used threshold is a positive SST departure from normal greater than or equal to +0.5°C.
What is a positive SST anomaly?
To calculate the Sea Surface Temperature (SST) Anomaly, we first needed to know the long-term mean SSTs globally. Areas in purple to blue mean a negative anomaly; that is, the water temperature is cooler than the mean. Orange to red means a positive anomaly: the temperature is warmer than the mean.
What is worse La Nina or El Niño?
La Niña is also sometimes called El Viejo, anti-El Niño, or simply “a cold event.” La Niña has the opposite effect of El Niño. During La Niña events, trade winds are even stronger than usual, pushing more warm water toward Asia. During La Niña winters, the South sees warmer and drier conditions than usual.
How long do El Ninos last?
9-12 months
El Niño and La Niña episodes typically last 9-12 months. They both tend to develop during the spring (March-June), reach peak intensity during the late autumn or winter (November-February), and then weaken during the spring or early summer (March-June).
