What does a positive SOI indicate?

A positive SOI indicates La Niña, while a negative SOI indicates El Niño.

What causes ENSO?

Although the exact initiating causes of an ENSO warm or cool event are not fully understood, the two components of ENSO – sea surface temperature and atmospheric pressure are strongly related. During an El Niño event, the easterly trade winds converging across the equatorial Pacific weaken.

What is SOI El Niño?

The Southern Oscillation Index, or SOI, gives an indication of the development and intensity of El Niño or La Niña events in the Pacific Ocean. The SOI is calculated using the pressure differences between Tahiti and Darwin. Sustained negative values of the SOI below −7 often indicate El Niño episodes.

What do you mean by ENSO?

El Niño-Southern Oscillation
The El Niño-Southern Oscillation (ENSO) is a recurring climate pattern involving changes in the temperature of waters in the central and eastern tropical Pacific Ocean.

Is La Niña positive or negative?

La Niña can have both positive and negative impacts on agriculture and food security. The main positive effect associated with La Niña is the increased likelihood of above-average rainfall. On the other hand, excessive rainfall induced by La Niña, can also result in flooding of farming land and pastures.

What happens during La Niña?

La Nina refers to the periodic cooling of ocean surface temperatures in the central and east-central equatorial Pacific. During a La Nina event, the changes in Pacific Ocean temperatures affect the patterns of tropical rainfall from Indonesia to the west coast of South America.

What is El Nino vs La Niña?

El Niño refers to the above-average sea-surface temperatures that periodically develop across the east-central equatorial Pacific. It represents the warm phase of the ENSO cycle. La Niña refers to the periodic cooling of sea-surface temperatures across the east-central equatorial Pacific.

Is La Niña Good or bad?

A climate pattern that occurs every few years, La Niña heralds broadly cooler and wetter conditions in the tropics. For important rainforest biomes in Southeast Asia and South America, experts generally agree that La Niña brings higher-than-average rainfall.

What does the SOI measure?

The SOI measures the difference in surface air pressure between Tahiti and Darwin. The index is best represented by monthly (or longer) averages as daily or weekly SOI values can fluctuate markedly due to short-lived, day-to-day weather patterns, particularly if a tropical cyclone is present.

What causes positive SOI levels during La Niña?

Prolonged periods of positive SOI values coincide with abnormally cold ocean waters across the eastern tropical Pacific typical of La Niña episodes.

What does a positive or negative SOI index mean?

The index is best represented by monthly (or longer) averages as daily or weekly SOI values can fluctuate markedly due to short-lived, day-to-day weather patterns, particularly if a tropical cyclone is present. Sustained positive SOI values above about +8 indicate a La Niña event while sustained negative values below about –8 indicate an El Niño.

What does the smoothed time series of SOI tell us?

In general, smoothed time series of the SOI correspond very well with changes in ocean temperatures across the eastern tropical Pacific. The negative phase of the SOI represents below-normal air pressure at Tahiti and above-normal air pressure at Darwin.