What Is El Nino: How Does It Affect Weather?

El Nino and La Nina are climactic events that affect weather on a global scale, forming off the coast of Peru every 2-7 years.

For hundreds of years fisherman living in coastal villages in Peru and Equador have known about El Niño. Once or twice every decade the normally cooler waters along South America's shores would warm. Fish would begin to die and then the seabirds that fed on the fish would starve by the thousands. The villagers lives and livelihoods

would suffer once the fish were gone. Fishermen named this event El Niño, which translated means, "The Little Boy" or "The Christ Child", because the phenomenon usually happened around Christmastime and might stretch far into the new year. But in time El Niño would fade, the ocean temperatures would return to normal, the great schools of fish would return and the simple life in the fishing villages went on.

In the days before radio, television and satellite communications, South American fishermen probably had no idea what other far-reaching climactic changes an El Niño produced beyond their shores. They couldn't know that whole continents suffered strange or reversed weather patterns. Or that normally arid regions were hit with torrential rains while more tropical lands suffered severe droughts. Sometimes snow fell where none had been seen in decades or even a century.

While South American scientists have been aware of El Niño's for a long time, their North American counterparts hadn't collected much data about this weather event, how it's formed and its potentially disastrous world-wide consequences. After the devastating El Niño of 1983, however, the scientific communities stood up and took more serious notice and began to gather the critical research they needed to learn more about El Niño.

Under normal climactic conditions a huge area of warm water is situated along the equatorial Pacific. Heating and evaporation builds storm clouds which are then carried west by the trade winds in a continuous cycle. Sea water lost to evaporation is replenished when cold water from the deep ocean rises, keeping temperatures closer to the surface at 60-70 degrees Fahrenheit. These conditions are ideal for fish and the many organisms they feed on to thrive.

During an El Niño the trade winds subside. Consequently the large area of warm water is not diminished by the continuous evaporation cycle, so instead widens, moving closer to the eastern tropics. No cold water rises from the depths so the waters continue to warm. This warming trend now begins to kill the important nutrients fish and other sea life need to survive. Once the fish disappear other animals who rely on them for food suffer mass starvation. As the warming continues, the trade winds die down even more, causing the regular weather patterns to signifi-

cantly alter, or in some cases, reverse. This climactic shift may cause torrential rains in deserts and droughts in temperate regions like Asia and Australia. Nor does North America go unscathed. During the last El Niño event in 1997 (the strongest ever recorded) California was drenched in heavy rains for weeks. The mid-west experienced a mild winter, followed by drought the following summer. Many other unusual weather conditions were felt well into 1998 and all around the globe.

El Niños seem to occur every 2-7 years. Once a cycle has run its course, atmospheric and oceanic conditions usually return to their normal patterns. In other less frequent cases another event called a "La Niña" follows close on the heels of her big brother. This is exactly what happened after 1997's very newsworthy El Niño was done wreaking his climactic havoc.

Translated, La Niña means, "The Little Girl" , but sometimes she is called "El Viejo", "anti-El Niño", or even just "a cold event". La Niña's occur when an excess of colder water rises in the tropical Pacific. This sudden surge causes the eastern trade winds to strengthen. Now too much cold water floods the upper ocean, causing temperatures to drop significantly, sometimes as much as 7 degrees below normal.

While an El Niño causes colder than normal winters in North America, a La Niña causes the opposite. For example, in the central plains of the US, drier than normal conditions would be the norm for fall and winter while regions in the Pacific Northwest received excessive rainfall. In 1997 El Niño's climactic interference created a relatively benign hurricane season. Not so La Niña. Once she was in full control a series of very damaging storms hit the United States, one right after the other.

Scientists have worked to create more sophisticated ways to track and predict when an El Niño and a La Niña will form, how strong they will become and even how each might impact global weather by using satellite observations, ocean buoys to record water temperatures, and sea level analysis. Interactive computer models of the Pacific Ocean and of atmospheric conditions are also being used to predict when and how strong the next El Niño and La Niña will be.

Climactic data points to another alarming fact - El Niño's have been occurring more frequently during the last 15-20 years. Some scientists believe this might be due to global warming. Others disagree. Still other researchers believe that there are only two climactic states - that of an El Niño year and that of a non-El Niño year. Whatever the case, scientists are keeping close tabs on global weather data as they wait for the next El Niño to be born off the coast of Peru. Will this one be stronger than the last and create even more climactic chaos? At this point in time it's too early to say.

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