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Droughts in India have historically been associated with El Nino, an anomalous warming of the equatorial Pacific, but scientists from Bengaluru suggest other culprits too
The Research
- Appears in journal Science
- The study was led by researchers at the Centre for Atmospheric and Oceanic Sciences (CAOS), Indian Institute of Science (IISc), Bengaluru.
- It says that 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.
Time Frame studies
- In an El Nino year, the rainfall deficit departure from a long-term average will set in early around mid-June and progressively worsen.
- However, a non-El Nino-year drought will see rainfall and will similarly weaken in midJune.
- But from mid-July to mid-August, usually the rainiest period of the monsoon, the monsoon will appear to recover.
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.
Source: The Hindu
