El Niño – and why we should be braced for an unusually dry summer

These observations on El Niño come from Brent Clothier, at Plant and Food Research…

All around the world, people are talking about El Niño. What is El Niño?

At the simplest level, El Niño is when a big puddle of warm water forms in the middle of the Pacific.  And the current puddle is big & warm.  The last comparable El Niño was in 1997/98. And there’s a great video of the inter-comparison at http://earthsky.org/earth/video-this-years-el-nino-compared-to-1997-98 . Here’s a screen grab of the comparison as at 3rd August …

el nino


According to the latest Update from the World Meteorological Organization there is

“… a mature and strong El Niño is now present in the tropical Pacific Ocean and is likely to strengthen further. This year’s El Niño event is the strongest since 1997-1998 and is potentially among the four strongest events since 1950. The peak strength of this El Niño, expected sometime during October 2015 to January 2016.”

What does this oceanic heating that is associated with El Niño do to atmospheric and oceanic flows?

El Nino 3

NIWA says

“…during El Niño, the trade winds weaken, leading to a rise in sea surface temperature in the eastern equatorial Pacific and a reduction of ocean upwelling off South America. Heavy rainfall and flooding occur over Peru, and drought over Indonesia and Australia. The supplies of nutrient rich water off the South American coast are cut off due to the reduced upwelling, adversely affecting fisheries in that region. In the tropical South Pacific the pattern of occurrence of tropical cyclones shifts eastward, so there are more cyclones than normal.”

So what’ll happen next now we’ve a strong El Niño?

We’ll get more westerly winds and NIWA has shown (below)

“…the average rainfall amounts, in percentage of the 1981-2010 normal, that were recorded for the summer season (December – February) during the three strongest El Niño events since 1950 (1972/73, 1982/83, 1997/98). Based on this record, an elevated risk for drought for parts of New Zealand is anticipated later during summer, in particular for eastern parts of both islands as well as northern areas of the North Island.”

El Nino 2

So in prospect we’re in for an unusually dry summer, especially in the north and east of both islands.

This has prompted the Ministry of Primary Industries to issue advice to farmers on how to prepare for this summer’s El Niño. It’s at https://www.mpi.govt.nz/protection-and-response/responding-to-threats/adverse-events/classifying-adverse-events-/preparing-for-el-nino/

This advice includes:

  • Have a plan in place with set dates for decisions depending on climate conditions. Discuss your plan with trusted advisers and update it over time.
  • Make decisions early and take action.
  • Use irrigation water efficiently and plan for water restrictions.

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