LA NINA

IN NEWS:

• The World Meteorological Organization (WMO) has declared that the La Niña weather phenomenon is back in the central and eastern equatorial Pacific Ocean after nearly a decade’s absence. It is expected to have profound impact on Indian weather in the coming months.

WHAT IS LA NINA:

• La Niña (Spanish for little girl) is one part of the El Niño-Southern Oscillation (ENSO) cycle, a complex phenomenon that takes place over the Pacific Ocean.
• The ENSO is an irregular periodic variation in the surface temperature of the water and winds over the Pacific Ocean. The other part of this cycle is El Niño.

• Both La Niña and El Niño are deviations from the normal surface temperatures of the Pacific Ocean. While La Niña is referred to as the cold phase of ENSO, El Niño is the warm phase of ENSO.
• El Nino-La Nina events have been found to impact almost half the world triggering floods in Australia, India, southern Africa and droughts in Peru, Ecuador, the United States, the Gulf of Mexico, and the Colorado River basin.
• La Niña and El Niño usually last between 9 and 12 months. While their frequency is fairly irregular, they take place every two to seven years. Typically, El Niño occurs more frequently than La Niña.
• La Nina this year is expected to be a moderate one, which means the impact on crops would be modest.

ORIGIN:

• In a normal year:
  • Winds along the equator push warm water westward. Warm water at the surface of the ocean blows from South America to Indonesia.
  • As the warm water moves west, cold water from the deep rises up to the surface. This cold water ends up on the coast of South America.
  • Rain clouds normally form over the warm ocean water and results in wet climates along the western margins of Pacific. However, the eastern margins witness relatively drier weather.

• In a La Niña year:
  • The equatorial winds are much stronger than usual. This bring more warmer waters to the western margins and makes the water near the western equatorial region a few degrees colder than it usually is.
  • This means that places like Indonesia and Australia can get much more rain than usual. However, the cold water in the eastern Pacific causes less rain clouds to form there. So, places like the southwestern United States can be much drier than usual.

LA NINA’S IMPACT ON INDIA:

• Increase in precipitation: Due to La Nina, the South-West monsoon has extended its tenure by three weeks this year, bringing more precipitation in October. This trend is expected to continue in the coming months.
• Harsh winters: In a La Niña year, equatorial winds blow much stronger during the winter, which makes the water near the equator a few degrees colder than normal. t would translate into intermittent waves of extremely cold weather, instead of a dip in temperatures throughout the season. This is already evident in Delhi. On October 29, Delhi recorded a minimum temperature of 12.5 degrees Celsius — the lowest in the month of October in 26 years.
• Other weather anomalies: Rare episodes like the “frost in Mahabaleshwar” and “cold waves in hilly parts of Tamil Nadu” can be associated with La Niña episodes. 
• Favorable for agriculture: Weak La Nina conditions have generally been favorable for Kharif crops. Longer precipitations result in increase in agricultural production from the rainfed areas and thus strengthen food security. However, sensitivity of different crops to La Nina episodes is not uniform for all the regions.
• Impact on global agricultural trade: The weather phenomenon is already creating an impact on the global production and price of crops such as wheat, coffee, sugarcane, palm oil. Global agricultural prices have shot up between 8 and 15 per cent in the last two months including wheat (up 14 per cent), maize (up 14.7 per cent) and sugar (up 9.3 per cent). This can affect India’s Agri export-imports sector.
• Potential hazards: While the cooling can reduce incidents of cyclones along Indian coasts, the erratic rainfall has the potential to create floods. Also, the added agricultural produce can generate deflationary trends in the country if not properly regulated.

DIFFICULTY IN PREDICTION:

• No direct correlation between the ENSO events and the monsoon has been established yet. Hence, with the present level of understanding, predicting the impact of La Nina accurately is a near-impossible task.
• Theoretically, El Nina events results in heavy or better monsoon rains in India, droughts in Peru and Ecuador, heavy floods in Australia, and high temperatures in the Indian Ocean and Western Pacific.
• However, this has not always been the case.
  • From 1950 to 2012, there were 16 La Nina years, with the monsoon rains ending up above or around average nearly every time.
  • El Nino brought in five droughts during this period but on 14 other occasions, monsoon performance ranged from being well below-average, average, or even above-average. In fact, the 1997-98 El Nino, among the century’s strongest, went on to generate above-average rain.

WAY FORWARD:

As climate change is expected to increase its foothold over global climate, El Nino-La Nina events are poised to become more frequent in the coming years. Hence, measures are essential to mitigate them.

• Short term: Since predictions are not fully reliable, the ideal strategy in the short run would be to improve upon the pillars of preparedness, response and mitigation. This can be achieved through:
  • Regular weather forecasting and periodic warnings.
  • Expanding farm insurance cover as a safety net for farmers.
  • Liquidating the extra stock of crops so as to absorb the surge in production.
  • Preparing a tight monetary policy to accommodate for the potential deflation.
  • Strengthen Public distribution systems
  • Taking measures to tackle deteriorating air quality that usually accompany harsh winters.
• Long term:
  • Encourage research and infrastructural investments in the field of meteorology so as to develop more reliable forecasting systems.
  • Encourage efficient agricultural practices like micro irrigation, use of water-stress resilient crops, development of storage facilities etc.
  • Improve upon India’s drought and flood mitigation measures.
  • Strengthening community watershed management and development.

PRACTICE QUESTION:

Q. Discuss the mechanism of La Nina. How can watershed management mitigate the impact of La-Nina over India?