During El Niño, what leads to increased rainfall over the Pacific?

• A. Cooling of surface waters causing high-pressure suppression of rainfall.
• B. Stable atmospheric conditions preventing cloud formation.
• C. Increased salinity causing heavier rainfall.
• D. During El Niño, warm water along the equator in the eastern Pacific warms the atmosphere, making air rise and rain.

Answer: (D)

When sea surface temperatures rise above average in the eastern Pacific, the overlying air becomes warmer and lighter. This warm air rises, cools as it ascends, and moisture condenses to form clouds and heavy rainfall. During El Niño, the eastern Pacific gets unusually warm and the trade winds weaken, allowing more warm water and moisture to spread eastward, which fuels stronger convection and rainfall across the central and eastern Pacific.

That description matches the mechanism driving the observed rainfall increase. The other options describe cooling, stable conditions, or salinity effects, none of which explain the enhanced convection and rainfall associated with El Niño.