Western Disturbance

In recent years it is observed that the arrival of frequency of the western disturbances has increased over the Indian subcontinent. What do you understand by western disturbances? Explain their origins, causes of increased frequencies and their effect on India. (200 Words)

Western Disturbances are low-pressure areas embedded in the Westerlies, the planetary winds that blow from west to east between 30 and 60° latitude. They originate in the Mediterranean region, travel westward and enter India loaded with moisture, where the Himalayas obstruct them, causing rain and snow over northern India. The moisture in these storms usually originates over the Mediterranean sea and Atlantic Ocean. WDs are important to the development of the Rabi crop in the northern subcontinent.
The frequency of western disturbance amplified because of presence of easterlies from Bay of Bengal. Also due to pronounced warming over the Tibetan plateau in recent decades which can be attributed to climatic warming, favours enhancement of meridional temperature gradients. The warming in recent decades over west central Asia led to an increase in instability of the western winds thereby increasing WDs leading to a higher intensity for heavy precipitation.
Such disturbances can damage crops resulting into economic as well as agricultural loss for the people and farmers. Farm output is affected when crops that are ready to be harvested or about to ripen, get soaked in excessive rainfall. This is a concern in states like Madhya Pradesh, Gujarat, Maharashtra and Rajasthan, Punjab and Haryana.
Little-understood western disturbances have been blamed for most of the freak weather events in India in the past decade. What do you understand by these ‘Western Disturbances’? How do they originate and what effect they have on India’s economy? Discuss. (200 Words)
Western Disturbance is the term used to describe an extra-tropical storm that brings sudden winter rain and snow to the north-western parts of the Indian subcontinent. This is a non-monsoonal precipitation pattern driven by the Westerlies.
Origination:
  1. The moisture in these storms usually originates over the Mediterranean Sea and the Atlantic Ocean.
  2. They carry moisture usually in the upper atmosphere (unlike tropical storms where it is carried in the lower atmosphere).
  3. In India, moisture is sometimes shed as rain when the storm system encounters with the Himalayas.
  4. In the Himalayan region of India, monsoon current progresses from east to west. But the WDs move across north India from west to east, with consequent rise in pressure and cold pool of air in the rear.
Effects on Economy:
  1. Western Disturbances are important to the development of the Rabi crop in the northern subcontinent, which includes the locally important staple wheat.
  2. Their effect sometime extends up to Gangetic plains and Northeast India, also.
But in the past few years western disturbances have been linked to disasters.
In this year hailstorm and rains in Gujarat, MP, UP and Rajasthan has caused severe damage to Cotton, Mango, Wheat and gram crops. It has weakened economic conditions of farmers in these states.
So, though beneficial, western disturbances are causing problems in agriculture output of India, due to climate change all over world.