DownToEarth-Southwest Monsoon 2020: Good rains now bring bad news

DownToEarth-Southwest Monsoon 2020: Good rains now bring bad news


After its onset over Kerala, the southwest monsoon season appears to be progressing according to schedule. However, there have been considerable variations in rainfall over what regions normally receive.

Recent Trends:

  • Tamil Nadu received 46 per cent less rainfall than what it receives during the period.
  • Puducherry and Kerala have recorded 23 per cent and 10 per cent less rainfall.
  • Central Indian states have received excess or large excess rainfall.
  • Madhya Pradesh has received the maximum 114 percent, excess rainfall, Chattisgarh a close second at 104 per cent.
  • Gujarat, Goa and Maharashtra too have received 67 per cent, 51 per cent and 49 percent more rainfall than what they receive during the period.
  • One of the reason for the difference could be Cyclone Nisarga, which formed in the Arabian Sea right around the time of the monsoon onset and pulled the monsoon moisture further inland into central India.

Highlight of ‘Assessment of Climate Change over the Indian Region’ Report

  • As per the first climate change assessment report for India published by the Union Ministry of Earth Sciences, this is a sign of a warming world.
  • The country’s average temperature has risen by 0.7 degrees Celsius (°C) since 1901 and it will increase to 4.4°C by end of the 21st century, relative to the recent past (1976-2005 average).
  • The summer monsoon rainfall has decreased over the country since 1950, particularly over the Indo-Gangetic plains and the Western Ghats.
  • The frequency of localised heavy rainfall has significantly increased over central India adding that extreme rains are concentrated around urban India.
  • Climate models suggest that the monsoon circulation will weaken in future, which will be compensated by increased moisture content in the atmosphere.
  • This will lead to an increase in the frequency of extreme precipitation events all over India, particularly over the central and southern parts.
  • While monsoon onset dates are likely to be early or not to change much, the monsoon retreat dates are likely to be delayed, resulting in longer monsoon seasons.

Problem of Locust

  • While such a monsoon pattern can throw agricultural activities into a disarray, it can also make locust attacks a perennial problem for the country.
  • Locusts usually arrive at the scheduled desert area of the country for breeding during the summer monsoon season and leave around October-November.
    • But this year, they arrived way ahead of the season and have since spread north and westwards in areas that had received ample unseasonal rainfall between March and May, due to western disturbances.
  • With monsoon rains already sweeping across the newly invaded states, entomologists fear that some swarms might not go to Rajasthan for breeding and instead rapidly mature and lay eggs at places wherever they find sandy or loam soil, resulting in localised outbreaks.
  • As per FAO, around 22 more swarms from Iran and southwest Pakistan will start moving towards the summer breeding areas along the Indo-Pakistan border and by early July, huge swarms developing in the Horn of Africa are likely to migrate across the Arabian Sea and arrive at Gujarat and Rajasthan.
  • If the monsoon’s retreat gets delayed, they will extend their stay — like last year — resulting in a prolonged and most severe locust invasion in decades. By the end of the year it might result in a locust plague.

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