El Niño, La Niña, and ENSO

🌐 El Niño, La Niña & ENSO – Made Easy

---

🌊 1. Normal Conditions in Pacific Ocean:

• Trade winds blow east → west (from South America to Asia).

• These winds push warm water toward Asia/Australia.

• Near South America, cold water rises to replace it — called upwelling.

• Indonesia & Australia: Get more rain.

• South America (Peru/Ecuador): Stays dry.

---

🔁 2. What is ENSO?

• ENSO = El Niño + Southern Oscillation (a natural climate cycle).

• It has 3 phases:

  1. Normal

  2. El Niño (warm phase)

  3. La Niña (cool phase)

• It affects global weather, agriculture, monsoons, and economies.

---

🔥 3. El Niño (Warm Phase of ENSO)

✅ Key Points:

• Sea temperature rises in the central and eastern Pacific.

• Trade winds weaken or reverse.

• Warm water moves back to South America.

• Indonesia, India: Less rain → droughts

• South America: More rain → floods

📌 Effects:

• ☁️ Weak monsoon in India

• 🌾 Crop failure, forest fires in Australia

• 🌊 Poor fishing in Peru (no upwelling)

• 🌀 Global weather changes (hurricanes, heatwaves)

---

❄️ 4. La Niña (Cool Phase of ENSO)

✅ Key Points:

• Sea temperature drops in the central and eastern Pacific.

• Trade winds become stronger.

• Warm water is pushed further west toward Asia.

• Indonesia, India: More rain → floods

• South America: Drier than usual

📌 Effects:

• 🌧️ Strong monsoon in India

• 🌾 Good crops in India, but floods possible

• 🔥 Wildfires in South America (dry conditions)

• ❄️ Colder winters in some regions

---

📝 Quick Revision Table:

Feature	Normal Year	El Niño (Warm)	La Niña (Cool)
Pacific SST (East)	Normal	Warmer than usual 🔥	Colder than usual ❄️
Trade Winds	Normal (East → West)	Weaken or reverse	Stronger than normal
Rain in India	Normal	Decrease (droughts)	Increase (good monsoon)
Rain in Peru/Ecuador	Dry	More rain (floods)	Drier than normal
Rain in Indonesia	Heavy	Less rain	More rain

---

📚 UPSC Tips:

• El Niño = Bad for Indian Monsoon 🌦️

• La Niña = Good for Indian Monsoon 🌧️

• ENSO monitored by NOAA and IMD.

• Important for agriculture, planning, disaster management.

---

UPSC MCQ's

Consider the following statements with reference to the El Niño-Southern Oscillation (ENSO) cycle: 

1.  1. During El Nino, trade winds are weakened and warm water is pushed back to the west coast of the Americas. 
2.  2. El Nino causes an increase in rainfall over the eastern tropical Pacific Ocean. 

 Which of the statements given above is/are correct?

 (a) 1 only 

 (b) 2 only

 (c) Both 1 and 2

 (d) Neither 1 nor 2

Comment the correct answer...