Which of the following statements is/are correct? 1. The jet streams are high altitude easterly winds. 2. El Niño is a warm ocean current. 3. El Niño appears along the Peru coast. Select the correct answer using the code given below.
- (a)1 only
- (b)2 and 3 only
- (c)1 and 3 only
- (d)1, 2 and 3
Correct — B, 2 and 3 only. Statement 1 reverses the direction of the jet streams. The polar-front jet and the subtropical jet both blow from west to east, driven by the sharp temperature contrast across a front and bent eastward by the earth's rotation; they were noticed during the Second World War precisely because pilots kept meeting strong westerly winds at high altitude. Easterly jets do exist — the tropical easterly jet forms over peninsular India in summer — but they are separate named features, and 'the jet streams' as a class are westerly. Statements 2 and 3 are the pair Indian geography textbooks state together: El Niño is the periodic appearance of a band of warm water off the coast of Peru and Ecuador, replacing the cold Peruvian current, and it takes its name from the Peruvian fishermen who noticed it arriving around Christmas.
- (a)1 only — It keeps the one statement that is wrong and drops the two that are right. Jet streams flow west to east, not east to west.
- (c)1 and 3 only — Statement 3 is indeed correct, but pairing it with statement 1 keeps the easterly error and leaves out statement 2.
- (d)1, 2 and 3 — This accepts all three, which would require jet streams to be easterly winds. The direction is the single falsifier in the set.
Jet streams are narrow ribbons of very fast wind in the upper troposphere, at roughly nine to twelve kilometres, flowing west to east at speeds that commonly reach 300 kilometres an hour and have been measured near 400. El Niño is a different animal altogether: a warming of surface water in the central and eastern equatorial Pacific that shows up along the South American coast, weakens the trade winds and, in India, is associated with a poorer south-west monsoon.
The question mixes one upper-air fact with two ocean facts, and only the upper-air one is wrong, so the answer hinges on remembering a direction. A useful anchor is that the westerly jet stream is why a flight from Delhi to Tokyo is quicker than the return leg. On statement 2, note the level at which it is being asked. Indian school geography defines El Niño as a warm ocean current replacing the cold Peruvian current, and the key follows that definition. Modern oceanography describes El Niño more fully as one phase of a coupled ocean-atmosphere oscillation across the whole Pacific rather than as a current in the narrow sense, but the textbook formulation is what the paper is testing and it is not wrong about the warmth or the location.
- The polar-front and subtropical jet streams flow from west to east; measured speeds reach about 400 kilometres an hour.
- The tropical easterly jet, which forms over peninsular India in summer, is a separate feature and does not make jet streams as a class easterly.
- El Niño is a warming of the eastern and central equatorial Pacific that appears off Peru and Ecuador, displacing the cold Peruvian current.
- The name comes from Peruvian fishermen, who saw the warm water arrive around Christmas.
- La Niña is the opposite phase, with unusually cold water in the same part of the Pacific, and it generally strengthens the Indian monsoon.
One false statement out of three, and it is the one about direction.
- Calling jet streams easterly because the trade winds are. The trades are surface winds of the tropics; the jets are upper-air westerlies.
- Assuming El Niño only affects South America. Its clearest Indian consequence is a weakened south-west monsoon.
- Treating El Niño and La Niña as unrelated events rather than the warm and cold phases of one oscillation.
As a statement set on winds and currents, as a comparison of El Niño with La Niña, or as a question on what El Niño does to the Indian monsoon.
La Nina is suspected to have caused recent floods in Australia. How is La Nina different from El Nino ? 1. La Nina is characterised by unusually cold ocean temperature in equatorial Indian Ocean whereas El Nino is characterised by unusually warm ocean temperature in the equatorial Pacific Ocean. 2. El Nino has adverse effect on south-west monsoon of India, but La Nina has no effect on monsoon climate. 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
Answer(d) Neither 1 nor 2
The same phenomenon tested on its geography rather than its warmth. Both statements there fail on the ocean involved and on the monsoon, and both errors are cousins of the direction error in statement 1 here.
Which one of the following is not a resultant of the El Nino effect?
- (a) Distortion of equatorial atmospheric circulation
- (b) Flow of the South-East Trade Winds towards the Indian Ocean
- (c) Irregularities in the evaporation of sea water
- (d) Reduction in the amount of planktons which reduces the number of fish in the sea
Answer(b) Flow of the South-East Trade Winds towards the Indian Ocean
El Niño again, from the consequences rather than the definition. The collapse of the Peruvian fishery listed there is the same warm-water intrusion off Peru that statement 3 describes.
- practice — not a real PYQ
The cold ocean current that El Niño temporarily displaces off the western coast of South America is the
- (a)Benguela current
- (b)Peruvian current
- (c)Canary current
- (d)Labrador current
Answer(b) Peruvian current — also called the Humboldt current; El Niño replaces its cold upwelled water with warm water.
- practice — not a real PYQ
In which layer of the atmosphere are the jet streams found?
- (a)Lower troposphere
- (b)Upper troposphere
- (c)Mesosphere
- (d)Thermosphere
Answer(b) Upper troposphere — roughly nine to twelve kilometres up, near the tropopause.