Understanding ENSO and the NINO3 Index

The question asks to identify which factor has a positive correlation with the NINO3 Index. The NINO3 Index measures sea surface temperature anomalies in the equatorial Pacific region (5°N-5°S, 150°W-90°W) and is a key indicator of the El Niño-Southern Oscillation (ENSO) phenomenon. ENSO significantly impacts global weather patterns, including rainfall and temperature.

A positive correlation means that as the NINO3 Index increases (indicating warmer Pacific temperatures, typical of El Niño), the related phenomenon also tends to increase. Conversely, a decrease in the NINO3 Index (indicating cooler Pacific temperatures, typical of La Niña) would correlate with a decrease in the phenomenon.

Correlation Analysis with NINO3 Index

• Indian Summer Monsoon Rainfall: El Niño events (high NINO3 index) are generally associated with weaker Indian summer monsoons and below-average rainfall. This suggests a negative correlation.
• Rainfall over Tamil Nadu during Northeast Monsoon: Studies indicate that El Niño conditions often lead to increased rainfall over Tamil Nadu during the northeast monsoon season (October-December). Conversely, La Niña conditions may bring less rainfall. This points towards a positive correlation.
• Temperature in Tamil Nadu during Northeast Monsoon: Temperature patterns are complex, but often rainfall and temperature show inverse relationships. A positive correlation with NINO3 for rainfall doesn't necessarily translate to temperature.
• Rainfall in Australia during Summer Monsoon: El Niño events typically bring drought conditions (reduced rainfall) to eastern and northern Australia. This indicates a negative correlation.

Conclusion on Correlation

Based on the typical impacts of ENSO, the rainfall over Tamil Nadu during the northeast monsoon shows a tendency towards a positive correlation with the NINO3 Index. Increased NINO3 Index values (El Niño) are often linked to enhanced rainfall in this region during this specific monsoon season.