According to a study led by researchers at the Centre for Atmospheric and Oceanic Sciences (CAOS), Indian Institute of Science (IISc), Bengaluru, not all Indian droughts are caused by El Nino.
- Actually, droughts in India have historically been associated with El Nino, an anomalous warming of the equatorial Pacific, but scientists from Bengaluru suggest that other factor is also responsible for this.
- The study that appears in journal Science says that nearly 6 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.
- The researchers say that 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 Rossby wave?
- According to the NOAA, Oceanic and atmospheric Rossby waves — also known as planetary waves — naturally occur largely due to the Earth’s rotation.
- These waves affect the planet’s weather and climate.
- Rossby waves help transfer heat from the tropics toward the poles and cold air toward the tropics in an attempt to return atmosphere to balance.
(Source: The Hindu and NOAA)
