3-fold rise in extreme rainfall events in Central India:

3-fold rise in extreme rainfall events in Central India:

Context:

According to a study published in the journal ‘Nature Communications’, there has been an increase in the frequency and intensity of extreme rainfall events across the Central Indian belt which extends from Gujarat in the west to Odisha and Assam in the east.

What does the report say?

• There has been an average 10% decline in summer monsoon (June to September) rainfall over central India between 1950 and 2015.
• This decline is due to the weakening of the summer monsoon winds.
• However, the frequency and intensity of extreme rain events (more than 150 mm per day for two-three days covering an area of 250 by 250 km) during the same period, has shown an increase.
• Climate projection models have also predicted an increase in extreme events over most parts of the Indian subcontinent by the end of this century.

Why is there a decline in monsoon rainfall?

• The temperature of the central Indian Ocean has increased.
• However, the Indian peninsular region has not warmed up compared to other regions in the tropics- This has led to a reduction in land-sea temperature difference.
• As a result of reduced land-sea temperature difference and cooling caused by aerosols, the monsoon winds have weakened and consequently, there is a decline in monsoon rainfall.

Why are extreme rainfall events rising across the Central Indian belt?

• As a result of the weakening of monsoon winds, there is less supply of moisture to the Indian subcontinent.
• The temperature in the northern Arabian Sea is rising, leading to more moist air over the Arabian Sea. The Arabian Sea contributes 36% of the total moisture to central India.
• As a result, there is large fluctuations in the monsoon winds
• This leads to occasional surges of increased moisture transport.
• These sudden surges of the monsoon winds bring in plenty of moisture and result in extreme rainfall events.