Monsoon Management

Context- India needs better science to prepare more effective disaster management plans and improve resilience in a warming world.

What is Long Period Average?

Long Period Average (LPA) – It is the average rainfall recorded during the months from June to September, calculated during the 50 year period, and is kept as a benchmark while forecasting the quantitative rainfall for the monsoon season every year.

  • First time since 2010 that India has got more than 100% of its long period average of 88cm in consecutive years.
  • Last year the country saw record rainfall of 110% of the LPA, the highest in a quarter century.
  1. IMD maintains five rainfall distribution categories on an all-India scale. These are-
  • Normal or Near Normal: When per cent departure of actual rainfall is +/-10% of LPA, that is, between 96-104% of LPA.
  • Below Normal: When departure of actual rainfall is less than 10% of LPA that is 90-96% of LPA.
  • Above Normal: When actual rainfall is 104-110% of LPA.
  • Deficient: When departure of actual rainfall is less than 90% of LPA.
  • Excess: When departure of actual rainfall is more than 110% of LPA.

What are the challenges of surplus rainfall?

  • Excess rainfall leads to floods, overflowing dams and loss of lives.
  • In hilly areas sudden rainfall brings landslide which damages natural and physical infrastructure subsequently disrupting human life economically as well as socially.
  • Surplus rains are not evenly distributed in time and space.

Therefore, much like there are attempts to improve flood forecast warnings, especially the short-term ones.

What are the reasons of excess rainfall this year in India?

  1. The heavy rains this year have been due to several long-lasting low-pressure systems in the Bay of Bengal that fuelled heavy rains over large swathes of India in August.
  2. A developing La Nina, the converse of an El Nino, which is a heating of the central equatorial Pacific and responsible for diminished monsoon rain over India, too contributed to munificent rains this year.

What are the technological measures taken to improve Disaster Management?

  1. 1. National Super-computing Mission– Supercomputers have also helped weather forecasters to accurately predict severe storms, enable better mitigation planning and warning systems.
  2. Monsoon Mission of India– This initiative of Ministry of Earth Sciences, launched in 2012, has utilized new approaches (high resolution, super parameterizations, data assimilation etc.) so that forecast skill gets quantitatively improved further for forecasting services of India Meteorological Department (IMD).
  • For the first time, IMD used the Monsoon Mission dynamical model to prepare operational seasonal forecast of 2017 monsoon rainfall over India.

Way forward

Scientists need to put in more effort and design research programmes that better analyses the vagaries of the northeast monsoon.


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