Thursday, May 29, 2014

EQUINOO Effect May Reduce El Nino Impact

Read our forecast: Monsoon 2014:  ‘Super’ El Niño is unlikely but rainfall deficiency can cross 16%!
Note EQUINOO is another terminology for Indian Ocean Oscillation (IOD). Wonder why they need to coin another terminology for the same phenomenon. Nonetheless the substance of the article remains interesting...

(Papiya Bhattacharya in IndianExpress) The warm phase of El Nino Southern Oscillation (ENSO) has already begun in April with increased rainfall over the Central Pacific. All weather models predict that it will amplify and persist until the end of the summer monsoon, according to Sulochana Gadgil, a meteorologist at the Centre for Atmospheric and Oceanic Sciences (CAOS) in Bangalore.

In an editorial in the latest issue of Current Science, she describes in detail the effects of a probable El Nino on rains in India.

The editorial talks about how the Indian monsoons depend on another phenomenon called the Equatorial Indian Ocean Oscillation (EQUINOO) and, if the dreaded El Nino shows effect this year, its bad effects may be neutralised by a favourable phase of EQUINOO.

Gadgil says there are uncertainties about an El Nino and, by mid-June, it will be known if the phenomenon will occur.
“In 2014, an unfavourable ENSO phase is expected, implying the probability of a drought of over 30 per cent. If an El Nino does develop, the chance of a drought increases to 70 per cent,” she says in the editorial.
In 2003, it was discovered that in addition to ENSO, EQUINOO plays an important role in the yearly changes in rains in India. According to Gadgil, EQUINOO involves a see-saw between a state with enhanced rainfall over western equatorial Indian Ocean and suppressed rainfall over eastern equatorial Indian Ocean (favourable phase) and a state with opposite signs of East-West rainfall anomalies.

El Nino refers to the process of warming of the sea surface around the coast of Peru due to warm sea currents with far-reaching consequences. The warm waters cause fish and birds to die.

A drought in India could only lead to a fall in GDP, says Gadgil. Studies of the impact of Indian Summer Monsoon Rainfall (ISMR) on the GDP and food grain production in India during 1954-2004 have shown that bad effects of droughts are worse than the good effects of rain. Nine such El Nino events have occurred since 1958. Of these, seven led to less rains, six of them being droughts.

However, the monsoon rainfall was above average in 1963 as well as during the strongest El Nino phenomenon of 1997. The editorial says,
“During the El Nino of 1972-73, severe droughts occurred in Australia, India, Brazil, etc., and heavy flooding occurred in Kenya and parts of Ecuador and Peru.”
Some of these climatic extremes may have a common reason — changes in sea surface temperatures in the Pacific Ocean (El Nino) and changes in the atmospheric sea-level pressure across the Pacific basin (the Southern Oscillation). These combined changes have come to be popularly referred to as El Nino, and in scientific literature as El Nino Southern Oscillation events. Most Indian science models predict and simulate ENSO and the ENSO-Indian monsoon link, but they do not simulate or predict the EQUINOO and the EQUINOO-Indian monsoon link correctly. Since the latter has a larger effect on the monsoons, it may mitigate the effects of El Nino this year, if it were to occur, the editorial concludes.

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