Select the incorrect statement from the following :

Correct — option (1), El Nino and La Nina are a kind of storm.

The stem asks for the incorrect statement. El Niño and La Niña are not storms. NOAA describes them as climate patterns in the Pacific Ocean that can affect weather worldwide, the opposite phases of the El Niño-Southern Oscillation (ENSO) cycle.

A storm is a short-lived weather disturbance. El Niño and La Niña episodes typically last nine to 12 months and can sometimes last for years.

They can shift rainfall and storm activity in distant regions, but that makes them drivers of weather, not storms themselves. The other three statements match NOAA's description.

The idea to remember: El Niño and La Niña are phases of an ocean–atmosphere climate pattern; El Niño brings weaker trade winds, La Niña stronger ones.

Why the others are wrong

• (2)
  During El Nino, there are fewer phytoplanktons off the coast. — This statement is correct, so it is not the answer. During El Niño, trade winds weaken and upwelling off the Pacific coast of the Americas weakens or stops.

  Upwelling normally brings nutrients up from the deep. Without them, NOAA notes, there are fewer phytoplankton off the coast.

• (3)
  During La Nina trade winds are stronger than usual. — This statement is correct, so it is not the answer. NOAA states that during La Niña events trade winds are even stronger than usual, pushing more warm water toward Asia.

  At the same time, upwelling increases off the west coast of the Americas, bringing cold, nutrient-rich water to the surface, the reverse of El Niño.

• (4)
  El Nino & La Nina are the climate patterns. — This statement is correct, so it is not the answer. NOAA calls El Niño and La Niña climate patterns in the Pacific Ocean that can affect weather worldwide.

  They are the opposite phases of the El Niño-Southern Oscillation (ENSO) cycle, which couples changes in Pacific sea-surface temperature with changes in the atmosphere.

  The booklet's Hindi column prints "मौसम के प्रतिरूप" (weather patterns) in this option. Booklet instruction 12 covers such differences: "If there is any sort of ambiguity/mistake either of printing or factual nature then out of Hindi and English Versions of the question, the English Version will be treated as standard." So the option is read as printed in English.

ENSO, the El Niño-Southern Oscillation, is a recurring shift in the tropical Pacific. "El Niño" refers to changes in ocean temperature; the "Southern Oscillation" refers to the matching swing in air pressure across the Pacific.

Normally, trade winds blow from east to west along the equator, piling warm surface water towards Asia, while cold, nutrient-rich water upwells off South America.

During El Niño the trade winds weaken and warm water spreads back east. During La Niña they strengthen and push more warm water west. Events occur every two to seven years on average, not on a regular schedule.

Key facts

• NOAA describes El Niño and La Niña as climate patterns in the Pacific Ocean that can affect weather worldwide.
• El Niño and La Niña are opposite phases of the El Niño-Southern Oscillation (ENSO) cycle.
• During El Niño, trade winds weaken; during La Niña, trade winds are even stronger than usual.
• Episodes typically last nine to 12 months; events occur every two to seven years on average, not on a regular schedule.
• During El Niño, upwelling off the Americas weakens or stops, leaving fewer phytoplankton off the coast.

Common traps

• El Niño and La Niña influence storms and rainfall, but they are climate patterns lasting months, not storms. Calling them storms confuses a cause with its effects.
• Weaker trade winds belong to El Niño; stronger-than-usual trade winds belong to La Niña. A statement that swaps the two phases looks plausible but is false.
• Fewer phytoplankton during El Niño follows from weaker upwelling: less cold, nutrient-rich water rises off the Americas, so phytoplankton decline rather than increase.

UnlockIAS compared this question with questions from other RAS Prelims papers and found none similar enough to link.

• practice — not a real PYQ

  During a La Niña event, which of the following happens in the equatorial Pacific?

  • (a)Trade winds weaken and warm water moves east
  • (b)Trade winds become stronger than usual and push more warm water toward Asia
  • (c)Upwelling off South America weakens or stops
  • (d)Coastal waters off South America become warmer than usual
  Answer(2) — In La Niña, trade winds are stronger than usual and push more warm water toward Asia. Options (1), (3) and (4) describe El Niño: weaker trade winds, weakened upwelling and warmer water off South America.
• practice — not a real PYQ

  El Niño and La Niña are opposite phases of which of the following?

  • (a)Indian Ocean Dipole
  • (b)Madden-Julian Oscillation
  • (c)El Niño-Southern Oscillation
  • (d)North Atlantic Oscillation
  Answer(3) — El Niño and La Niña are the warm and cool phases of ENSO. Option (1) is a sea-surface temperature contrast across the Indian Ocean; option (2) is an eastward-moving band of tropical cloud and rainfall; option (4) is a pressure pattern over the North Atlantic.