Effects of El Nino on Southwest Monsoon across India

Chennaiyil Oru Mazhaikkaalam
Reading Time: 2 minutes
The study on effects of El Nino across individual Met divisions of the country.  Business Line is carrying an article on 15th April based on this study done exclusively by COMK. We take this opportunity to thank Mr. Vinson Kurian for providing us a platform to show this study to the world.

A summary of the study done over 13 Met divisions individually.  These are the divisions with highest precipitation during SWM and cover major part of the country.
The period of study is from 1982 to 2012.  The range 90% to 110% has been considered as normal, anything above is excess and anything below is deficit.
The years where the Nino 3.4 region SST has crossed threshold limits have been considered as El Nino impacted years.
Some interesting points that come out of this exercise is
  1. The entire Gangetic Plain from Bihar to Western UP is seriously impacted during El Nino years with more than 7 out of 10 El Nino years resulting in deficit years.
  2. In the same context Odisha as a region is pretty much immune to the El Nino factor with only 2 years resulting in deficit
  3. Kerala Jharkhand & Chhattisgarh are regions which are impacted heavily by El Nino with 5 out of 10 years resulting in deficit
  4. West UP has had lesser than average rains in 9 out of 10 El Nino years.
  5. While Assam & Meghalaya is impacted 50% of the years when El Nino conditions existed neighboring Nagaland, Manipur Mizoram & Tripura Met Division sees a positive relationship with El Nino with 3 out of 10 El Nino years seeing excess rainfall 9 out of 10 El Nino years have seen lesser than average rains for Assam & Meghalaya.
  6. Evolving El Nino pretty much is a disaster for the Gangetic Plains.

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Overall if one analyses the precipitation by above average and below average ranking 7 out of 10 El Nino years have resulted in lesser than average precipitation. The exception to this is Odisha where 8 out of 10 El Nino years have resulted in above average precipitation.

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In 8 out of the 13 Met Divisions El Nino years have contributed to more than 50% of the deficit years with Western UP being the worst affected 8 out of 9 deficit years are a result of El Nino.