Which atmospheric effect weakens during an El Niño event, leading to altered rainfall patterns?

💡 Explanation

During an El Niño event, Pacific trade winds weaken because the sea surface temperature gradient decreases, which diminishes the Walker circulation, upsetting normal tropical rainfall. Therefore, weakened Walker circulation results, creating drought and flooding, rather than orographic lifting, Rossby waves, or subsidence which occur due to local terrain.

• Which landform feature is most likely to occur when a river's sinuosity is significantly increased?
• Which ventifact characteristic diminishes when persistent lee-side deposition occurs?
• Which risk increases when artificial levees constrict a river's floodplain during an extreme rainfall event?
• Which risk markedly increases within deep karst caves upon prolonged, widespread surface pavement?
• Which mechanism causes increased cirque erosion following deglaciation?
• Which outcome occurs when strike-slip faults experience sustained tectonic stress accumulation?