Positive Indian Ocean Dipole Conditions

The Indian Ocean Dipole (IOD), particularly its positive phase, describes a condition where sea surface temperatures (SST) and weather patterns across the Indian Ocean become anomalous.

Understanding Positive IOD

A positive IOD is characterized by:

• Cooler than average sea surface temperatures in the eastern Indian Ocean (off Sumatra and Java).
• Warmer than average sea surface temperatures in the western Indian Ocean (off the coast of Africa).
• Strengthened easterly wind anomalies across the equatorial Indian Ocean.

Analysis of Statements

Let's evaluate the given conditions based on the characteristics of a positive IOD:

• a) The Eastern Indian Ocean is warmer than the Western Indian Ocean: This describes the *negative* phase of the IOD, not the positive phase.
• b) The Eastern Indian Ocean is colder than the Western Indian Ocean: This aligns directly with the definition of a positive IOD, which features cooler eastern waters and warmer western waters.
• c) Excess anomalous rainfall in East Africa: The warmer waters in the western Indian Ocean during a positive IOD enhance evaporation and convection, often leading to increased rainfall in East Africa.
• d) The westerly wind anomaly is in the Eastern Indian Ocean: A positive IOD is associated with strengthened *easterly* winds, not westerly wind anomalies, across the equatorial region.

Conclusion

The conditions that co-occur with the positive Indian Ocean Dipole are:

• Statement b: The Eastern Indian Ocean is colder than the Western Indian Ocean.
• Statement c: Excess anomalous rainfall in East Africa.

Therefore, options b and c are the correct conditions.