Topics Covered: Important Geophysical phenomena such as earthquakes, Tsunami, Volcanic activity, cyclone etc.
Not all Indian droughts are caused by El Nino:
As per latest findings, nearly six out of 10 droughts, in non-El Nino years, that occurred during the Indian summer-monsoon season in the past century may have been driven by atmospheric disturbances from the North Atlantic region.
- In 2014, India saw a 14% rainfall deficit — or a drought — that wasn’t linked to El Nino and before that in 1986 and 1985.
Factors that influence these droughts:
- These droughts are a consequence of a sudden and steep drop in rainfall in late August.
- Winds in the upper atmosphere are interacting with a deep cyclonic circulation above the abnormally cold North Atlantic waters. The resulting wave of air currents, called a Rossby wave, curved down from the North Atlantic squeezed in by the Tibetan plateau and hit the subcontinent around mid-August, suppressing rainfall and throwing off the monsoon that was trying to recover from the June slump.
What is El Nino?
- El Nino is a climatic cycle characterised by high air pressure in the Western Pacific and low air pressure in the eastern.
- During this event, there is a warming of the sea surface temperature in the eastern and central equatorial Pacific Ocean.
- It is one phase of an alternating cycle known as El Niño Southern Oscillation (ENSO).
What causes El Nino?
- El Nino sets in when there is anomaly in the pattern.
- The westward-blowing trade winds weaken along the Equator and due to changes in air pressure, the surface water moves eastwards to the coast of northern South America.
- The central and eastern Pacific regions warm up for over six months and result in an El Nino condition.
- What is El Nino?
- What is La Nina?
- What is ENSO?
- When do these events occur?
- Impact of ENSO on Asia, Africa and Australia.
Discuss the impact of La Nina weather phenomenon on India.
Sources: the Hindu.