Wednesday, 7 March 2007

La Nina - El Nino

New data on sea-level heights from February 2007 show that the tropical Pacific Ocean has transitioned from a warm (El Nino) to a cool (La Nina) condition during the prior two months. The beginnings of a possible La Nina are indicated by blue area. It is not certain yet if this current cooling trend will eventually evolve into a long-lasting, well-developed La Nina.

La Nina often follows an El Nino episode and the two are essentially opposites. During a La Nina, trade winds are stronger than normal, and the cold water that normally exists along the coast of South America extends to the central equatorial Pacific. La Nina changes global weather patterns and is associated with less moisture in the air, resulting in less rain along the coasts of North and South America. Jason will continue to track this developing switch in the climate.

This image of the Pacific Ocean was produced using sea-surface height measurements taken by the U.S.-French Jason satellite. The image is based on the average of 10 days of data centered on Feb. 12, 2007, compared to the long-term average of observations from 1993 through 2005. In this image, places where the Pacific sea surface height is higher (warmer) than normal are yellow and red, and places where the sea surface is lower (cooler) than normal are blue and purple. Green shows where conditions are near normal. Sea-surface height is an indicator of the heat content of the upper ocean.

Image credit: NASA/JPL Ocean Surface Topography Team



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