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National Monsoon Mission GS: 3 EMPOWER IAS

 

National Monsoon Mission

In news:

  • The new monsoon model, called the Coupled Forecast Model (CFS), deployed by the IMD under the National Monsoon Mission (NMM) has failed to forecast the excess rainfall received during Aug-Sept 2019.

Important facts:

  • Uncertain prediction of monsoon was supposed to be the norm when India was technologically backward and economically a minor player.
  • With the economic boom in India, funds went into monsoon research and led to the development of a new model -- Monsoon Mission Coupled Forecast Model, abbreviated as CFS (standing for Coupled Forecast System) -- that promised to predict the season weather pattern accurately and prevent Indian farmers and people from the vagaries of the monsoonal uncertainty.
  • Failure to predict adequate monsoon show the unpreparedness of the administration, particularly in Bihar. Half of Bihar is still under floodwater and the other half is struggling to come to terms with the severe drought it has faced.

 

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Why IMD fails to predict rainfall correctly

  • Some independent weather scientists, writing analyses in various publications, expressed the reasons that IMD missed in assessing the strength of monsoon.
  1. One was the Indian Ocean Dipole, which gives an indication of the temperature condition for the sustenance of monsoon over mainland India. The readings were favourable at the end of July for a very strong monsoonal wind in August and September. But the IMD model failed to this factor in, somehow.
  2.  Weaker El Nino till almost middle of August. This meant the temperature in the Indian Ocean towards the mainland India was higher. This translates into a stronger flow of monsoon over India.

El Nino

This is a name given to the periodic development of a warm ocean current along the coast of Peru as a temporary replacement of the cold Peruvian current. ‘El Nino’ is a Spanish word meaning ‘the child’, and refers to the baby Christ, as this current starts flowing during Christmas. The presence of the El Nino leads to an increase in sea-surface temperatures and weakening of the trade winds in the region.

How did it come about?

  • El Nino was observed as far back as in the late 1800s when South American fishermen noticed the warming up of coastal waters around Christmas. They referred to it as “El Nino” (Spanish for the boy child), since it appeared around Christmas.
  • Sir Gilbert Walker, a British mathematician, discovered the Southern Oscillation (SO), or large-scale changes in sea level pressure across Indonesia and the tropical Pacific. However, he did not recognise that it was linked to changes in the Pacific Ocean or El Nino.
  •  It wasn’t until the late 1960s that Norwegian-American meteorologist Jacob Bjerknes and others realised that the changes in the ocean and the atmosphere were connected.
  • As already mentioned, El Nino has been found to impact almost half the world triggering droughts in Australia, India, southern Africa and floods in Peru, Ecuador, the United States, the Gulf of Mexico, and the Colorado River basin. If Sir Gilbert found in the 1920s that many global climate variations, including monsoon rains in India, were correlated with the SO, the credit of linking it with El Nino as part of ENSO involving both the ocean and atmosphere, goes to Bjerknes. But it took until the 1980s or later for ‘La Nina’ or even the ‘neutral phase’ (neither El Nino or La Nina) to gain currency.

Effects of El Nino

  • El Nino affects global weather. It favors eastern Pacific hurricanes and tropical storms.
  • Recorded unusual rainfall in Peru, Chile, and Ecuador are linked to the climate pattern.
  • El Nino reduces the upwelling of cold water, decreasing the uplift of nutrients from the bottom of the ocean. This affects marine life and sea birds. The fishing industry is also affected.
  • Drought caused by El Nino can be widespread, affecting southern Africa, India, Southeast Asia, Australia, and the Pacific Islands. Countries dependent on agriculture are affected.
  • WHO report on the health consequences of El Nino forecasts a rise in vector-borne diseases, including those spread by mosquitoes, in Central and South America. Cycles of malaria in India are also linked to El Nino.
  • Over India, the El Nino has usually been the harbinger of drought and the La Nina of rain.

 

 

Past estimation of IMD:

  • This year is not a singular year when the IMD has failed to predict monsoon correctly.
  • In 2017, IMD said monsoon prediction has improved in recent years and claimed accuracy of 90 per cent for 1988-2008.
  • However, its record over the last few years has been dismal.
  •  The IMD has got a correct prediction only once since 2014 (in 2015). These years have also been part of a period when the climate change debate has dominated the environmental space.
  • In 2012, the IMD predicted that the monsoon would bring 104 per cent of the long period average of rainfall. The actual was at 93 per cent.
  • The 2013 prediction was in the range of accuracy. The IMD model predicted 104 per cent of long period average. It was 106 per cent of LPA.
  • In 2014, the actual rainfall was 88 per cent against the prediction of a normal monsoon by the IMD at 96 per cent of average rainfall. Modi government was welcomed with two consecutive drought years.
  • Another stark gap was witnessed in 2016, when the IMD's dynamic CFS model predicted monsoonal rain at 112 per cent. The actual was 97 per cent. The actual rainfall that year was in the zone of normal monsoon, which came after two consecutive years of drought.
  • This year,(2019) IMD's CFS model predicted a 97 per cent of the normal, but the monsoon has already brought 110 per cent of rainfall.

What is Monsoon Mission Coupled Forecast Model (CFS)?

  • It was deployed by the IMD (India Meteorological Department) under National Monsoon Mission (NMM).
  • It has failed to forecast the excess rainfall received during August-September 2019.

About Coupled Forecast Model (CFS):

  • It is a dynamical model which is also called Climate Forecast Model (CFS).
  • It has been developed based on a climate model developed by National Center for Environmental Prediction (NCEP), U.S. and it has been implemented on Prithvi High Performance Computers (HPC) at Indian Institute of Tropical Meteorology (IITM), Pune.
  • The Dynamical models employ a different approach to forecasting monsoon i.e. they roughly relies on capturing the interactions between land, ocean and atmosphere and tracking how the changes in each affect other.
  • The land, atmosphere and ocean state at a particulate time (generally March) is mathematically simulated on supercomputers and extrapolated into monsoon month.

About National Monsoon Mission (NMM):

  • It was has launched by Union Ministry of Earth Sciences (MoES).
  • The Ministry has bestowed the responsibility of execution and coordination of this mission to Indian Institute of Tropical Meteorology (IITM), Pune.

Mission Objective:

To build an ocean atmospheric model for

  • Improved prediction of monsoon rainfall on extended range to seasonal time scale of up to 16 days to about one season
  • Improved prediction of rainfall, temperature as well as extreme weather events on short to medium range time scale up to 15 days.

 

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Indian monsoon:

  • The term monsoon has been derived from the Arabic word mausin or from the Malayan word monsin meaning ‘season’.
  • Monsoon refers to a seasonal change in the direction of the prevailing winds of a region. It arises due to a difference in temperature between the landmass and the adjacent ocean. Monsoons cause wet and dry seasons throughout much of the tropics and are most often associated with the Indian ocean.
  • Monsoons are seasonal winds (Rhythmic wind movements)(Periodic Winds) which reverse their direction with the change of season.
  • The monsoon is a double system of seasonal winds – They flow from sea to land during the summer and from land to sea during winter.
  • Some scholars tend to treat the monsoon winds as land and sea breeze on a large scale.
  • Monsoons are peculiar to Indian Subcontinent, South East Asia, parts of Central Western Africa etc..
  • They are more pronounced in the Indian Subcontinent compared to any other region.
  • Indian Monsoons are Convection cells on a very large scale.
  • They are periodic or secondary winds which seasonal reversal in wind direction.
  • India receives south-west monsoon winds in summer and north-east monsoon winds in winter.
  • South-west monsoons are formed due to intense low pressure system formed over the Tibetan plateau.
  • North-east monsoons are associated with high pressure cells over Tibetan and Siberian plateaus.
  • South-west monsoons bring intense rainfall to most of the regions in India and north-east monsoons bring rainfall to mainly south-eastern coast of India (Southern coast of Seemandhra and the coast of Tamil Nadu.).
  • Countries like India, Indonesia, Bangladesh, Myanmar etc. receive most of the annual rainfall during south-west monsoon season where as South East China, Japan etc., during north-east rainfall season

Factors that influence the onset of south-west monsoons

  • Subtropical Jet Stream (STJ).
  • Tropical Easterly Jet (African Easterly Jet).
  • Inter Tropical Convergence Zone.

Factors that influence the intensity of south-west monsoons

  • Strengths of Low pressure over Tibet and high pressure over southern Indian Ocean.
  • Somali Jet (Findlater Jet).
  • Somali Current (Findlater Current).
  • Indian Ocean branch of Walker Cell.
  • Indian Ocean Dipole.

Factors responsible for north-east monsoon formation

  • Formation and strengthening of high pressure cells over Tibetan plateau and Siberian Plateau in winter.

  • Westward migration and subsequent weakening of high pressure cell in the Southern Indian Ocean.
  • Migration of ITCZ to the south of India.

Impact of monsoon on economy:

  • Monsoon has progressed more slowly than usual after hitting Kerala nearly a week late. Monsoon rains have been 44% lower-than-average so far in June, delaying the sowing of summer-sown crops and raising concerns that parts of the country could face a worsening drought. This shortfall could have a major impact on consumer demand, the overall economy and financial markets.

On health:

  • Because regions with a monsoon climate have distinctly wet and dry seasons, they are prone to floods and droughts, both of which are hazardous to health.

On agriculture:

  • Farmers in monsoon regions rely on the wet summer months to grow crops. However the summer monsoon does not always bring the same amount of rainfall, and variations in rain have implications for agriculture and the economy.

 

Conclusion:

For a country like India, where farmers still depend on monsoon for irrigation, the general population for drinking water, correct prediction of monsoon becomes a key factor for the overall well-being of the country and its economy. A correct prediction might also awaken a usually laid-back administration for rescue efforts if and when needed. Bihar flood is a case in point.

 

 

Source)

https://www.indiatoday.in/news-analysis/story/record-monsoon-in-25-years-why-imd-fails-to-predict-rainfall-correctly-1606093-2019-10-04