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| | | El Niño-Southern Oscillation (ENSO) |
Maintained by IOC
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| | History | | | | In 1891, Peruvian geographers suggested a link between an anomalously long rainy season and the presence of a north/south flowing warm water current off the Peurvian coast to the Lima Geographical Society. This coastal current, which brought with it unusually bountiful amounts of dolphinfish, yellowfin tuna, and bonito, was called 'el corriente del Niño' (the little boy's current) by local fishermen because of its occurrence near Christmas time. In 1895, Alfonso Pezet gathered his colleague's information and data and produced a paper titled, 'The Countercurrent El Niño off the coast of Northern Peru.' In 1924, Gilbert Walker, searching for a method to predict the Indian monsoons, recognized that changes in pressure zones and precipitation patterns in the Pacific seems to be linked in a see-saw oscillation with those in the Indian ocean, which he called the Southern Oscillation. Some forty years later, Jacob Bjerknes of the University of California at Los Angeles proposed a hypothesis based on the interaction of the ocean and the atmosphere to explain these two related phenomena of El Nino and the Southern Oscillation (ENSO). | | | | ENSO Defined | | | .2002-5-30.gif) An ENSO event is a natural, coupled atmospheric-ocean cycle that occurs in the tropical Pacific ocean on an approximate time scale of 2-7 years with varying intensity. Its intensity is often classified using indices (One commonly used index is the Southern Oscillation Index (SOI) that is based on sea level pressure differences between Darwin and Tahiti. Another is based on a measure of upper ocean temperatures that indicate the anomalous warmth or coolness of the equatorial Pacific temperatures). The warm (El Niño) phase of an ENSO event has been associated with regional extremes in precipitation. Severe droughts occur in some places (e.g., Indonesia) while torrential rains with flooding occur in others (e.g., Peru). The cold (La Niña) phase tends to produce the opposite effects in these regions. | | | | The neutral phase is indicative of normal conditions, i.e., with the normal trade winds blowing westward across the Pacific Ocean pushed by the atmospheric pressure difference, which is high in the east (Tahiti) and low in the west (Darwin). The warm (El Nino) phase occurs with a reversal of the wind direction and an eastward movement of the warmer waters. The cold (La Nina) phase is the result of anomalously high westward-blowing winds, which produce strong upwelling and a westward movement of the warmest waters along the equator. The area of strongest convective activity in the atmosphere follows the movement of the warmest waters along the equator and the impact on the weather of these coupled changes is felt globally, most severely in the tropics, but also, depending on intensity, to a lesser degree at somewhat higher latitudes. | | | | |
 | | | | | NASA TIES EL NIÑO INDUCED DROUGHT TO FIRES
by NASA's Goddard Space Flight Center, Press Release 02 April 2003 | |
| | Scientists using NASA satellite data have found the most intense global pollution from fires occurred during droughts caused by El Niño. The most intense fires took place in 1997- 1998 in association with the strongest El Niño event of the 20th century. | |
Read more at http://www.gsfc.nasa.gov ... ught.html.
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