El Nio hindered

Another pacific phenomenon holds up the wild child

Last Updated: Saturday 04 July 2015

-- the latest sea surface temperature ( sst) data from the us and French topex / Poseidon satellite shows that, while La Nia has subsided, there are no signs of a resurgent El Nio ( www.science. nasa.gov , June 28).

Instead, "the west may be looking at more of the same hot, dry weather," says, Bill Patzert, oceanographer at the us National Aeronautical and Space Administration's Jet Propulsion Laboratory. For countries, such as India, the findings could have implications for the monsoon patterns.

El Nio occurs when the trade winds subside and a great mass of warm water -- bigger than Canada -- moves towards South America. Rains that would normally soak the western Pacific shift toward the Americas, while places like Australia, Indonesia and India experience drought. El Nio normally lasts for one year. Then, resurgent trade winds move the warm surface waters back across the Pacific giving rise to La Nia.The back and forth rhythm of La Nia and El Nio is a normal part the Pacific Ocean's 'lifecycle'. There are similar oscillations in other oceans.

But this year the Pacific Decadal Oscillation ( pdo) could be holding the El Nio at bay. Patzert predicts a record-breaking fire season in the us this year. Already in Florida unusual wildfires have scorched the Everglades. pdo is a widespread pattern of sea-surface temperatures in the Pacific Ocean that cycles back and forth between two opposite phases every 10 to 20 years, as compared to El Nio-La Nia cycles which occur every 2 to 7 years. In the 'negative' phase of the pdo cycle, warmer waters in the north surround cooler surface waters in the eastern part of the Pacific, west and south. Negative pdo s appear in sea surface temperature maps as a 'horseshoe' of warm water surrounding a cooler 'wedge'.

Such a pattern is now visible in the Pacific using satellite imagery. That's why dry conditions are likely to persist in many parts of North America even though La Nia has faded. The negative pdo is picking up where La Nia left off. In the 1950s, 60s, and 70s, when the negative pdo was prevalent, El Nios were less frequent and weaker. The ongoing negative pdo could increase our wait for a new El Nio and weaken it when it does arrive.

Subscribe to Weekly Newsletter :

Comments are moderated and will be published only after the site moderator’s approval. Please use a genuine email ID and provide your name. Selected comments may also be used in the ‘Letters’ section of the Down To Earth print edition.