Question

<!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> "La Nina conditions result in increased rainfall and harsher winter in India". Explain.

Answer 1

Answer:

Introduction:

La Nina means ‘little girl’ in Spanish and is also known as El Viejo or ‘cold event. La Nina is an ocean-atmospheric coupled weather phenomenon. It occurs in the pacific ocean. It is a colder counterpart of El-Nino. Both are antagonistic to each other. El-Nino warms the eastern pacific than normal and thus weakens the trade winds coming to India. They occur once in three to four years.

Body:

Process of La Nina:
During the La Nina event, water temperature in the eastern pacific gets colder than normal.
This strengthens the high pressure in the eastern equatorial pacific ocean.
Thus, the trade winds start blowing towards the western pacific with higher intensity. I.e. strong winds blow warm water at the ocean’s surface from South America across the Pacific Ocean towards Indonesia
Thus upwelling increased in the south American coast and the warm air coming to India furthers lowers the pressure over the Indian ocean.
This in turn attracts the winds from the south-west monsoon.
La Nina events are said to occur if sea-surface temperature decreases of more than .5 degrees Celsius for at least five successive three-month seasons.

Impacts of La Nina:

Global impacts:
It causes drought in Peru and Ecuador i.e. countries bordering the western pacific. It is due to the colder climate which in turn increases the intensity of the dry winds, thus causing drought-like conditions.
It causes heavy floods in Australia. Warmer conditions around Australia bring in stronger trade winds that carry moisture along with itself. Thus it causes excessive rains sometimes leading to floods.
High temperatures in Western Pacific, Indian Ocean, off the Somalian coast.
Impacts on India:
On Monsoon: La Nina strengthens monsoon winds and thus the intensity of rains in India increases. Thus it strengthens the monsoon in India, sometimes even leading to floods.
On winters: La Nina strengthens the North-south Low-pressure system which in turn brings Siberian air and extends cold waves to the far South. Thus it may cause excessive cold during winters.

Other Impacts:
On Agriculture: It can contribute to better productivity especially in rain-fed areas, due to increased rainfall
On water crisis: It can help in combating water crises, if excessive rainwater is used to recharge natural and manmade aquifers, etc.
Disaster planning: In a la-Nina year, it forces the state agencies to be ready for mitigating unfortunate events such as floods, if they occur. This requires better forecasting.
On Economy: A good monsoon provides ample economic opportunities, with better crops. However, it sometimes hampers transportation thus impacting economic activity.

Conclusion:
Thus La Nina has several positive impacts on Indian agriculture which is of huge importance to the Indian economy and society both. However, this boon can be converted into a disaster, which can be easily mitigated by better planning and forecasting techniques.