Indian Monsoons in 2021
- September 28, 2021
- Posted by: OptimizeIAS Team
- Category: DPN Topics
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Indian Monsoons in 2021
Subject – Geography
Context – This year, a four-point monsoon story with a storm at each end
Concept –
- As of Monday, the country had received 850.3 mm of rain, 2% short of the season’s normal.
- With rainfall in 24% deficit of the Long Period Average (LPA), this August was the sixth driest since 1901. Since 2009, only one other August has been drier.
Reasons for deficit rainfall in August –
- Fewer low-pressure systems: They are the main source of monsoon rainfall, and only two of these systems — instead of the normal four — developed over the Bay of Bengal this August. At least two of these systems normally intensify into depressions.
- Position of monsoon trough: With no low-pressure systems forming, the monsoon trough remained to the north of its normal position for most days in August. As a result, rainfall was largely restricted to parts of Uttarakhand, Himachal, UP, and Bihar.
- Western Pacific Typhoons: These usually bring good rain during August as they cross Myanmar. Their remnants then re-enter the Bay of Bengal, become fresh weather systems and approach the Indian mainland along the east coast. “This August, typhoon activity was far less, and hardly any of their remnants reached the Bay of Bengal.
- The typhoons that developed recurved north-eastward instead of advancing north-westward towards the Bay of Bengal. The absence of low-pressure systems brought less rain over Central India.
- Negative Indian Ocean Dipole: Since the start of the monsoon, the IOD has remained in its negative phase. Studies have linked the negative phase of IOD to below normal rainfall.
- Off-shore trough: An off-shore trough that generally runs between Gujarat and Kerala, attracts moist winds from the Arabian Sea towards land, causing heavy rain in Gujarat and coastal Maharashtra, Goa, Karnataka, Kerala. This off-shore trough was largely absent last month. Without the off-shore trough, south-westerly monsoon winds that bring heavy rain over the west coast, remained significantly weak.
- Madden Julian Oscillation : This eastward-moving pulse of clouds brings rainfall along the Equator during a 30-60-day cycle. In August, these waves were prevailing near Africa, thus not helping cloud formation over India.