Which pattern is associated with cooler eastern Pacific and drier conditions?

• A. El Niño is associated with warmer eastern Pacific and increased rainfall.
• B. La Niña is associated with cooler eastern Pacific and drier conditions.
• C. Neutral ENSO shows no temperature anomalies.
• D. El Niño and La Niña always occur together.

Answer: (B)

In ENSO patterns, La Niña brings cooler-than-average sea surface temperatures in the eastern Pacific because the trade winds strengthen and push warm water west while upwelling brings cooler water to the surface off South America. This cooling reduces convection and rainfall in the eastern Pacific, leading to drier conditions there. It’s the opposite of El Niño, which warms the eastern Pacific and usually increases rainfall in that region. Neutral means no strong temperature anomalies. The idea that El Niño and La Niña always occur together isn’t correct; they are alternating phases of the same cycle.