Context: Amid the revival of monsoon since the second week of July, there has been a significant variation in rainfall across the country.

More in the news:

  • Several parts of the western Konkan coast and the southern peninsula were witnessing instances of extreme rainfall.
  • According to the India Meteorological Department data on the regional distribution, the ‘South Peninsula’ received 29% more rain than normal during the period June1-July 23 of the year 2021.
    • In the same period, northwest and central India witnessed a 10% and 2% deficit respectively and northeast India a 14% deficit, though this region has a higher base rainfall than other regions.
  • July and August are the most important monsoon months, contributing over two-thirds of the seasonal rainfall. 
    • Central India and the southern peninsula are expected to see most of the rainfall. 
    • However, climate scientists have warned that monsoon patterns overall have been changing.

Probable cause:

  • The frequency and strength of cyclones over the Arabian Sea have increased in the past two decades. 
    • There is a 52% increase in the frequency of cyclones over the Arabian Sea from 2001 to 2019 and an 8% decrease over the Bay of Bengal compared with the period 1982-2002. 
    • Even the duration of cyclones has increased by 80%. 
    • More cyclones were bringing in more moisture from the Arabian Sea and contributing to extreme rainfall events.

Related Facts

Impact of Climate Change on rainfall pattern on western coast:

  • The frequency of low-pressure systems in the Bay of Bengal has declined, this extra moisture is transported in from the Arabian Sea. 
  • Monsoon winds (westerlies) over the northern Arabian Sea are exhibiting increased variability (large fluctuations), driving surges of moisture supply, leading to extreme rain episodes across the entire central Indian belt.
    • This is due to the increased warming north of the Arabian Sea, as a result of increased anthropogenic (human-led) activities resulting in carbon emissions. 
  • The warm ocean temperatures in the northern Arabian Sea results in increased moisture and large fluctuations of the monsoon winds.

Map of Indian Coastal Plain: