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 outcome occurs when seasonal subtropical high-pressure systems weaken?
• Which outcome arises when tectonic uplift decreases a lake's catchment area and inflow?
• Which outcome accelerates coastal erosion when streams carrying sediment are dammed?
• Which mechanism increases subsurface water content when permafrost thaws during warmer summers?
• Which outcome occurs when lahars block valley passages?
• Which outcome results from unchecked agricultural soil deflation?