El Nino and La Nina
· The two important
meteorological events as far Indian sub continent is concerned are monsoons
(southwest monsoon and northeast monsoon) and cyclones, which generally form
during the pre-monsoon (March-May) and the post-monsoon season
(October–December).
· The two important
phenomena which influence the Indian Ocean are the El Nino and Southern Oscillation (popularly known as ENSO) and the Indian Ocean Dipole that refers to the difference
in temperatures between the surface waters in the west and east of the ocean.
· El Nino can further be classified into two types— traditional El Nino which is characterized by
strong anomalous warming in the eastern equatorial Pacific and the El Nino Modoki that is associated with
strong anomalous warming in the central tropical Pacific and cooling in the
eastern and western tropical Pacific.
· Monsoon in India will be governed by where and when
this El Nino is formed and how strong or weak it would be.
Q. What is the impact?
· El Nino and La Nina
can both have global impacts on weather, wildfires, ecosystems, and economies.
· Episodes of these
climate patterns typically last nine to 12 months, but can sometimes last for
years.
· El Nino and La Nina
events occur every two to seven years, on average, but they don’t occur on a
regular schedule.
· Generally, El Nino occurs more frequently than La
Nina.
Q. What are differences between El Nino and La Nina?
|
El Nino |
La Nina |
|
· During El Niño, trade winds
weaken. Warm water is pushed back east, toward the west coast of the
Americas. · El Niño also has a strong
effect on marine life off the Pacific coast. During normal conditions,
upwelling brings water from the depths to the surface; this water is cold and
nutrient rich. During El Niño, upwelling weakens or stops altogether. · Without the nutrients from the
deep, there are fewer phytoplankton off the coast. This affects fish that eat phytoplankton and, in turn, affects
everything that eats fish. The warmer waters can also bring tropical species,
like yellowtail and albacore tuna, into areas that are normally too cold. |
· During La Niña events, trade
winds are even stronger than usual, pushing more warm water toward Asia. Off
the west coast of the Americas, upwelling increases, bringing cold,
nutrient-rich water to the surface. · These cold waters in the
Pacific push the jet stream northward. This tends to lead to drought in the
southern U.S. and heavy rains and flooding in the Pacific Northwest and
Canada. During a La Niña year, winter temperatures are warmer than normal in
the South and cooler than normal in the North. La Niña can also lead to a
more severe hurricane season. · During La Niña, waters off the
Pacific coast are colder and contain more nutrients than usual. This
environment supports more marine life and attracts more cold-water species,
like squid and salmon, to places like the California coast. |
|
Test
Yourself-II
Q.
La Nina is suspected to have caused recent floods in Australia. How is La
Nina different from El Nino? (Prelims 2011) 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
Q.With
reference to ‘Indian Ocean Dipole (IOD)’ sometimes mentioned in the news
while forecasting Indian monsoon, which of the following statements is/are
correct? (2017) 1.
IOD phenomenon is characterised by a difference in sea
surface temperature between tropical Western Indian Ocean and tropical
Eastern Pacific Ocean. 2.
An IOD phenomenon can influence an El Nino’s impact on the
monsoon. Select
the correct answer using the code given below: (a)
1 only (b)
2 only (c)
Both 1 and 2 (d)
Neither 1 nor 2
Ans: (b) UPSC Mains PYQs
Q. Most of the unusual climatic happenings are explained as
an outcome of the El-Nino effect. Do you agree? |
