La Nada Event In Pacific
September 10, 2013

La Nada Happening In The Pacific

Brett Smith for - Your Universe Online

Based on data from one of NASA’s orbiting satellites, experts at the National Weather Service’s Climate Prediction Center have found near-normal sea-surface height conditions across the equatorial Pacific Ocean, indicative of a so called “La Nada” event. The weather experts added that the condition has persisted for 16 months, since spring 2012 and will continue through the spring of 2014.

“Without an El Niño or La Niña signal present, other, less predictable, climatic factors will govern fall, winter and spring weather conditions,” said climatologist Bill Patzert of NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California.

"Long-range forecasts are most successful during El Niño and La Niña episodes. The 'in between' ocean state, La Nada, is the dominant condition, and is frustrating for long-range forecasters. It’s like driving without a decent road map - it makes forecasting difficult.”

About 50 percent of the past few decades have been under La Nada conditions, compared to about 20 percent for El Niño and 30 percent for La Niña. According to Patzert, some of the wettest and driest winters have taken placed during La Nada periods.

“Neutral infers something benign, but in fact if you look at these La Nada years when neither El Niño nor La Niña are present, they can be the most volatile and punishing,” he said. “As an example, the continuing, deepening drought in the American West is far from ‘neutral.’”

The surface height of ocean water can partially be correlated to its temperature, making it an indicator of heat that is stored in the ocean below. As ocean water warms,  its level rises; as it cools, it falls. An image released by NASA showed relatively flat, or temperate, water.

The image generated by NASA data is an indicator of processes that occur over the course of a more than a year, but typically less than a decade. These processes are referred to as the interannual ocean signal.

NASA scientists say they will continue to monitor this La Nada event to determine how the Pacific Ocean will impact future world climate.

El Niño, La Niña and La Nada are all part of the evolving state of global climate, which can be measured via sea surface height. The satellite used to create the latest image, Jason-2, is operated under joint effort between NASA, the National Oceanic and Atmospheric Administration (NOAA), the French Space Agency Centre National d'Etudes Spatiales (CNES) and the European Organization for the Exploitation of Meteorological Satellites (EUMETSAT).

Starting in 2015, NASA, NOAA, CNES and EUMETSAT are expected to launch Jason-3, which will extend the data of ocean surface topography measurements started by the Topex/Poseidon satellite in 1992. Jason-3 will also record detailed measurements of sea level topography to better understand ocean circulation and climate change.

A January 2012 report was the last time NASA scientists found evidence of something other than La Nada based on their topography data. The lower-than-normal sea surface heights in the equatorial Pacific seen by the Jason satellites pointed to La Niña conditions.

"Conditions are ripe for a stormy, wet winter in the Pacific Northwest and a dry, relatively rainless winter in Southern California, the Southwest and the southern tier of the United States," Patzert said at the time.