The question asks to identify the anomalous feature that is NOT associated with El Nino events.

El Nino Characteristics Explained

El Nino is a complex climate pattern involving the unusual warming of surface waters in the eastern tropical Pacific Ocean. Key associated features include:

• Sea Surface Temperature: Anomalous warming in the eastern equatorial Pacific.
• Thermocline Depth: The thermocline, separating warm surface water from cold deep water, deepens significantly in the eastern Pacific and becomes shallower (shoals) in the western Pacific. This is due to weakened trade winds and altered ocean currents.
• Rainfall Patterns: The area of intense rainfall typically shifts eastward from the western Pacific towards the central and eastern Pacific.

Analysis of Options

Let's evaluate each option based on typical El Nino conditions:

• Option 1: Deepening of thermocline in the western equatorial Pacific - This is contrary to El Nino conditions, where the thermocline typically shoals (becomes shallower) in the west. Therefore, this is the anomalous feature NOT associated with El Nino.
• Option 2: Shoaling of thermocline in the western equatorial Pacific - This is a characteristic feature of El Nino as the warm water suppresses upwelling in the west.
• Option 3: Surplus rainfall in central and/or eastern tropical Pacific - El Nino causes a shift in weather patterns, leading to increased rainfall in these regions.
• Option 4: Warming of eastern equatorial Pacific - This is the defining characteristic of an El Nino event.

Conclusion

The feature that is NOT associated with El Nino is the deepening of the thermocline in the western equatorial Pacific.