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15th April 2022 (6 Topics)

IMD forecasts ‘normal’ monsoon, no El Nino

Context

India Meteorological Department (IMD) forecasted a ‘normal’ southwest monsoon for 2022. Meanwhile, it downgraded the definition of what is an average rainfall.

About

IMD’s Monsoon Forecast for 2022

  • IMD updated long period average rainfall to 87 cm. India would get 99% of the long period average (LPA) rainfall.
  • Last change in long period average (LPA) rainfall was in 2018 where it was changed from 89 cm to 88 cm, and now is again revised to 87 cm.
  • A monsoon is considered “normal” when rainfall falls between 96% and 104% of the LPA.
  • There will be a weak El Nino indicating a negligible adverse impact on Indian monsoon while there will be a favourable La Nina phenomenon.

India Meteorological Department

  • It is an agency established in 1875 under the Ministry of Earth Sciences.
  • It is the principal institution responsible for meteorological observations, weather forecasting and seismology.

Long Period Average                                                                      

  • LPA is the averages of rainfall received over a 50-year period between 1951 and 2001 which comes to 89 cm of rainfall.
  • It recorded during the months from June to September.
  • It is set as a benchmark while forecasting the quantitative rainfall for the monsoon season every year. 
  • Following are the five rainfall distribution categories on an all-India scale maintained by IMD:

    • Excess:When departure of actual rainfall is more than 110% of LPA.
    • Above Normal:When actual rainfall is 104-110% of LPA.
    • Normal or Near Normal:When per cent departure of actual rainfall is +/-10% of LPA, i.e., between 96-104% of LPA.
    • Below Normal:When departure of actual rainfall is less than 10% of LPA,  e., 90-96% of LPA.
    • Deficient:When departure of actual rainfall is less than 90% of LPA.

About El Nino

  • El Nino (Spanish for Christ Child) is the occasional development of warm ocean surface waters along the coast of Ecuador and Peru.
  • The El Nino normally occurs around Christmas, roughly every 2 to 7 years and lasts usually for a few weeks to a few months.
  • El Nino and the Indian Monsoon rains are inversely related. It results in hotter than usual summers and drought-like conditions.
  • About La Nina
  • La Nina is a climate pattern that describes the cooling of surface ocean water along the tropical west coast of South America.
  • It is considered as the counterpart of El Nino, and its impacts tend to be opposite those of El Niño.
  • Together, they form the "cold" (La Nina) and "warm" (El Nino) phases of the El Nino-Southern Oscillation (ENSO).

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