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Reasons for India’s bouts of extreme weather

Context:

Kerala and Uttarakhand have received incessant rainfall in October 2021 leading to doubts over the potential role of climate change behind these extreme weather events. In both these States and other states as well, over the last few years, there have been variations in the pattern and intensity of rainfall.

Relevance:

GS-III: Environment and Ecology (Climate Change and its Impact, Conservation of Environment, Effects of Environmental Pollution), GS-III: Disaster and Management (Natural and Anthropogenic Disasters, Disaster Management in India)

Dimensions of the Article:

  1. Recent extreme rainfall events
  2. Cause of Extreme Rainfall Events
  3. Factors contributing to torrential rains
  4. Connection with global warming

Recent extreme rainfall events

  • Several parts of the western Konkan coast and the southern peninsula were seeing instances of extreme rainfall with the ‘Southern Peninsula’ region seeing almost 30% more rain than normal during the June-July period.
  • Recently, Mahabaleshwar in western Maharashtra reported over 60cm of rainfall in just one day which “exceeded its all-time record” according to the IMD.
  • Rainfall, the IMD said the torrential rains over the Konkan coast was likely to continue for the rest of the week due to the position of the monsoon trough.
  • July and August are the most important monsoon months contributing over two-third of the seasonal rainfall and central India as well as the south Peninsula are expected to see most of the rainfall during this interim.
  • However, climate scientists have warned that monsoon patterns, overall have been changing.

Cause of Extreme Rainfall Events

  • The frequency and strength of cyclones over the Arabian Sea has increased in the last two decades.
  • There is a 52% increase in the frequency of cyclones over Arabian Sea from 2001-2019 and 8% decrease over Bay of Bengal compared to 1982-2002, when historically most cyclones have been in Bay of Bengal, according to a study
  • Even the duration of these cyclones has increased by 80%. More cyclones were bringing in more moisture from the Arabian Sea and contributing to extreme rainfall events.

Factors contributing to torrential rains

  • There have been two rain-bearing ‘low pressure systems’ that are active in the Arabian Sea as well as the Bay of Bengal. The low pressure system in the Arabian Sea has contributed significantly to the heavy rain in Kerala. Winds from the Bay of Bengal low pressure system have been reaching as far as Uttarakhand and contributing to rainfall in northern parts of India.
  • Western disturbances are periodic influxes of moisture-laden clouds from the Mediterranean which are common during winter. String western disturbances are contributing to heavy rain in northern India.
  • This year, the monsoon began its retreat on early October and though it was expected to fully retreat by mid-October, it is yet to completely withdraw, with the associated clouds still lingering on and thus contributing to continued rainfall activity. October is the month when the southwest monsoon entirely retreats from India.

Connection with global warming

  • The generation of low pressure systems and the western disturbances are connected to the larger pattern of global warming.
  • Global warming is leading to increased sea temperatures in general giving rise to enhanced cyclonic activities. The heating effect has been more intense in the Arabian Sea, thus leading to significant cyclonic activity in the Arabian Sea region.
  • Overall elevated temperatures are contributing to warmer waters in the Arctic Ocean and is subsequently drawing colder air from the poles with greater intensity. This added to the increased moisture in the atmosphere is leading to more intense western disturbance activity over north India. As air temperature increases, air can hold more water molecules.
  • Warming oceans are contributing to intense spells of rainfall in pockets followed by long rainless spells. This is being considered as one of the most visible manifestations of climate change.

-Source: The Hindu

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