Case Study: Can you see the El Niñ

El Niño graphic courtesy of Visit to an Ocean Planet CD ROM produced by TOPEX/Posiden Project NASA

Drought and flood, fire and famine; the symptoms are apparent and yet the causes of El Niño remain mysterious. The suffering produced by the cycle is familiar to those that have endured its wrath. Although the causes of the dramatic changes in ocean circulation remain a mystery, the installation of earth observing satellites in recent decades has allowed scientists to more closely track the emergences of the oceanic conditions that signal the start of the El Niño and La Niña cycle. This early detection gives hope that someday soon we will be able to warn nations that an El Niño is coming.

The objective of this exercise is to illustrate the methods used to detect and track El Niño and its sister pattern, La Niña. This early pattern detection has allowed for the mitigation of some of the devastating environmental and human consequences attributable to the El Niño induced changes in normal weather patterns.

El Niño conditions in the Pacific Ocean.
NOAA/PMEL/TAO.

El Niño, or "the Child", is the name given to an unusually warm and persistent countercurrent that appears off the coast of Peru at irregular, 3-7 year, intervals by Peruvian farmers. This name was given to the current because it usually appeared around the time of the Christmas holidays. Unlike the Peruvian fishermen who named the current 100 years ago, we now know that the triggers of this unusual countercurrent are changes in the patterns of normal oceanic and atmospheric temperatures and pressures.

Once considered merely a local phenomenon, the El Niño pattern is now recognized as a sign of a larger shift in oceanic circulation which alters currents globally. The impacts of this reversal are significant and can include drought in Australia and Indonesia and floods on the coasts of North and Central America.

La Niña conditions in the Pacific Ocean.
NOAA/PMEL/TAO.

Often occurring in sequence with El Niño is La Niña. The La Niña pattern, bringing cooler than normal sea surface temperatures to the Pacific Ocean, is important in its own right. La Niña follows a similar cyclical pattern as its counterpart, El Niño. La Niña is also associated with unusual global weather events. Due to the disruption of the jet streams, these events can be as disparate as heavy rains in the Northwest United States and a decrease of hurricanes in the Atlantic basin. Once developed, these events can last a year or more.