La Nina is suspected to have caused recent floods in Australia. How is La Nina different from EI Nino?

1. La Nina is characterized by un­usually cold ocean temperature in equatorial Indian ocean whereas EI Nino is characterized by unusually warm ocean temperature in the equatorial Pacific Ocean.
2. EI Nino has adverse effect on south­west monsoon of India, but La Nina has no effect on monsoon climate.

Which of the statements given above is/are correct?

[UPSC Civil Services Exam – 2011 Prelims]

(a) 1 only

(b) 2 only

(c) Both 1 and 2

(d) Neither 1 nor 2

Answer: (d)

Explanation:

• La Nina:
  • Definition: Also known as a ‘cold event’ with unusually cold ocean temperatures in the Equatorial Pacific.
  • Effects: Creates strong high pressure over the eastern equatorial Pacific and low pressure in the Western Pacific and off Asia. Causes drought in Peru and Ecuador, heavy floods in Australia, high temperatures in Western Pacific, Indian Ocean, off the Somalian coast, and good monsoon rains in India.
• El Nino:
  • Definition: Refers to the warming of sea surface temperatures across the central and east-central Equatorial Pacific.
  • Effects: Associated with high pressure in the western Pacific. Opposite of La Nina. Rainfall follows the warm water eastward, with associated flooding in Peru and drought in Indonesia and Australia. Adversely impacts the Indian monsoons and hence, agriculture in India.

Therefore, option (d) is the correct answer.