Q. Consider the following statements regarding the Southern Oscillation Index (SOI):

1. Southern Oscillation Index (SOI) is an index for gauging the strength of El Nino and La Nina.
2. The index is best represented by monthly (or longer) averages.
3. Sustained positive SOI values above about +8 indicate a La Nina event while sustained negative values below about -8 indicate an El Nino.

Which of the above statements is / are correct?
Answer: 1, 2 and 3
Notes: The Southern Oscillation Index (SOI) is a primary atmospheric index used to monitor the strength of El Niño and La Niña phenomena. The index is ideally represented by monthly or longer averages for accuracy. Typically, sustained SOI values above +8 correlate with La Niña events, while sustained values below -8 indicate El Niño conditions.