Portraits of Earth: El Niño and La Niña

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 The Earth. Text, this is the world we study most from space. A fleet of orbiting observations helps us understand forces and phenomena that shape the Blue Planet. 

Viewspace Special Feature, Portraits of Earth. El Niño, La Niña. The Winds of Change. Title, Driven by the Oceans. 

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The oceans drive Earth's weather. A thermal map of the globe with land masses dark and the ocean pulsing with bright colors. Text, Pacific Ocean temperatures in 2007, red is warm blue is cold. El Niño and La Niña are changes in ocean temperatures, coupled with changes in ocean winds, that can wreak havoc around the globe. Large blue section moves across ocean. 

El Niño and La Niña begin in tropical waters of the Pacific Ocean. Normal Trade Wind Pattern. In the Pacific, the trade winds blow from South America toward Australia and Indonesia. Illustration of arrow labeled trade winds pointing from Peru to Australia. Text, These trade winds push warm surface water away from Peru and Ecuador, causing cooler water to rise to the surface. Warm water pushed on top with wind, cold water rises. Text, The cooler water is rich in nutrients and so it attracts school of hungry fish and fishing boats. A fish and dollar sign appear next to Peru. 

Title, El Niño, Weak Trade Winds. Every few years though the pattern changes and the trade winds weaken. El Niño Wind Pattern. The weaker trade winds push less warm water toward Asia so less cold water rises. Surface waters near South America stay warm. Illustration showing weak trade winds arrow pushing from Peru to Australia. Warm water doesn't move away from Peru, cold water doesn't rise. This is an El Niño. 

Thermal map of globe with red area near South America. Text, Warmer than normal temperatures (shown in red) existed off the coast of South America during the 1997-98 El Niño. The effects are evident in South America around Christmas and assumed the name "El Niño," Spanish for "the little boy." Photo of empty fishing boats lining a beach in Chile. The effects of El Niño can be devastating to local economies. With no upwelling of cool water and nutrients, fish migrate away and the South American fisheries suffer. 

Thermal maps. May 10, 1998, Warm El Niño Waters. Decreased Plankton Levels. May 25, 1998, Cooler Waters. Healthy Plankton Levels. On the left, warm and nutrient-poor El Niño waters have wiped out plankton, a key food source for fish, around the Galapagos Islands. On the right, as cooler water returns, so does the plankton, high levels appear red. 

Colored rainfall map of South America. Text, The warm water also feeds heavy rains, bringing floods to South America. This map shows just how much more rain than usual fell in parts of South America during an El Niño season in December 2006 and January 2007. Blue and green show places with higher-than-normal rainfall and cover areas of Brazil, Paraguay, Argentina, Uruguay. 

Overhead map of coast. Text, El Niño brings heavy rain to the west coast of North America as well. Normal coast vs. waterlogged El Niño coast. In 2002, huge El Niño-related storms dumped rain on northern California, causing flooding of rivers and lakes. Large blue areas. Photo of cliff next to coastal homes. Text, During the El Niño season from 1997 to 1998, high waters along the California coast caused massive beach erosion. 1998 El Niño-related erosion near Esplanade Drive in Pacifica, California. Photo of flooded homes. Heavy rains also caused floods. Parts of Lakeport, California flooded during the 1998 El Niño. 

Aerial view of mountains, lake. A great brown landslide covers the landscape. Text, The most expensive single landslide in U.S. history was caused by El Niño storms. Heavy rain in central Utah during 1982 and 1983 triggered a huge landslide, which in turn created a lake. The lake flooded a town, three major highways, and an important railway line. 

Fishing boats sitting on a tiny lake surrounded by dried, cracked earth, Text, Meanwhile, with no strong trade winds to push warm ocean water to Asia, the normal Asian monsoons which are fed by warm water come late or not at all. This causes severe drought in places like Indonesia and the Philippines. Thailand's Lam Takhong Dam, where waters have dried up due to prolonged drought. 

Title, La Niña, Strong Trade Winds. Often, El Niño is followed by La Niña. La Niña wind pattern. During La Niña, which means "the little girl," the trade winds strengthen on their way from the Americas to Asia. Illustration of arrow labeled strong trade winds moving from Peru to Australia. Text, Just the opposite of El Niño, La Niña intensifies the cold upwelling of sea water off Peru and Ecuador. Illustration of warm water moving with wind and cold water rising by Peru. Text, Abundant cold nutrient-rich water near the South American coast results in a fishing bonanza. Dollar signs and fish appear next to Peru. 

Thermal map of the globe. Text, Red shows warmer than average ocean temperatures in November 2007. While La Niña brings cool water to the eastern Pacific, it leads to warmer water near Asia and Australia. Warm, moist air is forced upward by the strong trade winds and fuels storms in the western Pacific. Instead of the drought brought on by an El Niño, La Niña overwhelms southeast Asia and Australia with rain. 

Aerial view of flooding in Australia during La Niña in January 2008, large areas of blue on the green land. 

Satellite view of Hurricane Lili pushing into the Gulf of Mexico on October 2, 2002 during La Niña. El Niño suppresses hurricanes, but during La Niña cooler water pushes the jet stream to the north. The globe encircled with pulsing colored bands near the equator. Hurricane Generation Zone. El Niño water highlighted red. La Niña, the water becomes blue and the bands push north. Text, With the jet stream out of the way, hurricanes tend to form more easily. 

Photo of a cone-shaped tornado extending from cloud to Earth. Text, Tornadoes in the southern part of the U.S. also appear to be more common during La Niña season. This could be in part because La Niña seasons are normally associated with warmer-than-average air temperatures in the American south. Map of the U.S. with colored zones labeled, "Tornado Alley" in the center, Cold Dry Air moving down from northwest, Warm Dry Air moving up from Mexico, Warm Moist Air moving up from Gulf of Mexico. Text, The collision between extra-warm air in the south with cold air to the north sets the stage for a tornado outbreak. Photo of a large dark tornado. Text, The 1999 (La Niña) severe weather season started early with a record-setting number of tornadoes, mostly in the southeastern United States. In January, 169 twisters occurred in 6 southern states. Video loop of clouds moving across Oklahoma. Text, On May 3, 1999 tornadoes in Oklahoma killed at least 40 people and caused over 500 million dollars in damage. 

Title, Satellites Help Us Predict. Text, In the past it was impossible to know when El Niño or La Niña might strike. Today, thanks to Earth-observing satellites that monitor ocean temperatures and global wind patterns, scientists are better able to predict the consequences of El Niño and La Niña and provide timely warnings. Illustration of satellites circling globe on yellow paths.