A new image, based on the average of 10 days of data centered on Jan. 26, 2013, shows near-normal conditions (depicted in green) across the equatorial Pacific. The image is available at: http://sealevel.jpl.nasa.gov/images/latestdata/jason/2013/20130126P.jpg.
This latest image highlights the processes that occur on time scales of more than a year, but usually less than 10 years, such as El Niño and La Niña. These processes are known as the interannual ocean signal. To show that signal, scientists refined data for this image by removing trends over the past 20 years, seasonal variations and time-averaged signals of large-scale ocean circulation.
The height of the water relates, in part, to its temperature, and thus is an indicator of the amount of heat stored in the ocean below. As the ocean warms, its level rises; as it cools, its level falls. Yellow and red areas indicate where the waters are relatively warmer and have expanded above normal sea level, while green (which dominates in this image) indicates near-normal sea level, and blue and purple areas show where the waters are relatively colder and sea level is lower than normal. Above-normal height variations along the equatorial Pacific indicate El Niño conditions, while below-normal height variations indicate La Niña conditions. The temperature of the upper ocean can have a significant influence on weather patterns and climate. For a more detailed explanation of what this type of image means, visit: http://sealevel.jpl.nasa.gov/science/elninopdo/latestdata/.
"This past spring, after two years of La Niña, the expected El Niño was a no-show," says Bill Patzert, climatologist at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "La Niña faded and 'La Nada' conditions locked in. This absence of El Niño and La Niña, termed 'neutral' by some, has left long-range climate forecasters adrift," Patzert added. "Seasonal, long-range forecasting works best when signals like El Niño and La Niña are strong."
Patzert calls the present condition 'La Nada,' because the word 'neutral' misleadingly implies to some that weather will be 'normal.'....
The latest image of sea surface heights in the Pacific Ocean from NASA's Jason-1 satellite shows that the equatorial Pacific Ocean is now in its 10th month of being locked in what some call a neutral, or "La Nada" state. "La Nadas" make long-range climate forecasting more difficult due to their greater unpredictability. Yellows and reds indicate areas where waters are relatively warmer and have expanded above normal sea level, while blues and purple areas show where waters are relatively colder and sea level is lower than normal. Green indicates near-normal sea level conditions. Image credit: NASA-JPL/Caltech/Ocean Surface Topography Team