Fires and floods, droughts and hurricanes - all together fell on our Earth in 1997. Fires turned the forests of Indonesia to ashes, then raged in the vastness of Australia. Showers are frequent over the Chilean Atacama Desert, which is particularly dry. Heavy rains and floods did not spare South America either. The total damage from the willfulness of the elements amounted to about $ 50 billion.
Meteorologists believe that the cause of all these disasters is the El Niño phenomenon.
The term "El Niño" was first used in 1892 at the congress of the Geographical Society in Lima. Captain Camilo Carrilo said the name "El Niño" was given to the warm north current by Peruvian sailors, as it is best seen on Catholic Christmas. In 1923, Gilbert Thomas Walker began to study the zonal convective circulation of the atmosphere in the equatorial zone of the Pacific Ocean and introduced the terms "Southern Oscillation", "El Niño" and "La Niña". Until the end of the twentieth century, his work remained known only in narrow circles, until the connection between El Niño and the planet's climate change was established.
El Niño means "baby" in Spanish. This affectionate name reflects only the fact that El Niño most often begins during the Christmas holidays, and fishermen on the west coast of South America associated it with the name of Jesus in infancy.
In normal years, along the entire Pacific coast of South America, due to the coastal rise of cold deep waters caused by the surface cold Peruvian Current, the ocean surface temperature fluctuates within narrow seasonal limits - from 15 ° C to 19 ° C. During the El Niño period, the ocean surface temperature in the coastal zone rises by 6-10 ° C. As evidenced by geological and paleoclimatic studies, this phenomenon has existed for at least 100 thousand years. Fluctuations in ocean surface temperature from extremely warm to neutral or cold occur with periods ranging from 2 to 10 years. Currently, the term "El Niño" is used in relation to situations when abnormally warm surface waters occupy not only the coastal region near South America,but also most of the tropical Pacific Ocean up to the 180th meridian.
There is a constant warm current originating from the coast of Peru and extending to the archipelago lying southeast of the Asian continent. It is an elongated tongue of heated water, equal in area to the United States. The heated water intensively evaporates and "pumps" the atmosphere with energy. Clouds form over the heated ocean. Usually trade winds (constantly blowing easterly winds in the tropical zone) drive a layer of this warm water from the American coast towards Asia. Around Indonesia, the current stops, and monsoon rains fall over the south of Asia.
At El Niño in the equatorial region, this current warms up more than usual, so the trade winds weaken or do not blow at all. The heated water spreads to the sides, goes back to the American coast. An abnormal convection zone appears. Rains and hurricanes hit Central and South America. Over the past 20 years, there have been five active El Niño cycles: 1982-83, 1986-87, 1991-1993, 1994-95 and 1997-98.
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The La Niño phenomenon, the opposite of El Niño, manifests itself as a decrease in surface water temperature below the climatic norm in the east of the tropical Pacific Ocean. Such cycles were noted in 1984-85, 1988-89 and 1995-96. Unusually cold weather sets in the East Pacific during this period. During the formation of La Niño, the trade winds (easterly) winds from the west coast of the Americas are significantly stronger. The winds shift the zone of warm water and the "tongue" of cold waters stretches for 5000 km, exactly in that place (Ecuador - Samoa), where during El Niño there should be a belt of warm waters. During this period, powerful monsoon rains are observed in Indochina, India and Australia. The countries of the Caribbean and the United States are suffering from droughts and tornadoes. La Niño, like El Niño, occurs most often from December to March. The difference isthat El Niño occurs on average once every three to four years, and La Niño - once every six to seven years. Both events bring with them an increased number of hurricanes, but during La Niño there are three to four times more of them than during El Niño.
According to recent observations, the credibility of an El Niño or La Niño offensive can be determined if:
1. Near the equator, in the eastern part of the Pacific Ocean, a patch of water warmer than usual (El Niño), colder (La Niño) is formed.
2. Compares the trend in atmospheric pressure between the port of Darwin (Australia) and the island of Tahiti. Under El Niño, the pressure in Tahiti will be high, but in Darwin it will be low. With La Niño, the opposite is true.
Research over the past 50 years has shown that El Niño means more than just coordinated fluctuations in surface pressure and ocean temperature. El Niño and La Niño are the most pronounced manifestations of interannual climate variability on a global scale. These phenomena represent large-scale changes in ocean temperatures, precipitation, atmospheric circulation, vertical air movements over the tropical Pacific Ocean.
Abnormal weather conditions on the globe during the El Niño years
In the tropics, precipitation increases over areas east of the central Pacific Ocean and decreases from normal in northern Australia, Indonesia and the Philippines. In December-February, more than normal precipitation is observed along the coast of Ecuador, in northwestern Peru, over southern Brazil, central Argentina and over equatorial, eastern Africa, during June-August in the western United States and over central Chile. El Niño events are also responsible for large-scale air temperature anomalies around the world. These years have seen outstanding temperature rises. Warmer than normal conditions in December and February were over southeast Asia, over Primorye, Japan, the Sea of Japan, over southeast Africa and Brazil, southeastern Australia. Warmer than normaltemperatures are observed in June-August along the west coast of South America and over southeastern Brazil. Colder winters (December-February) occur along the southwest coast of the United States.
Abnormal weather conditions on the globe during the La Niño years
During the La Niño periods, precipitation increases over the western equatorial Pacific Ocean, Indonesia and the Philippines, and is almost completely absent in the eastern part. Most precipitation falls in December-February over northern South America and over South Africa, and in June-August over southeastern Australia. Drier than normal conditions are observed over the coast of Ecuador, over northwestern Peru and equatorial eastern Africa during December-February, and over southern Brazil and central Argentina in June-August. Worldwide, there are large-scale abnormalities with the highest number of areas experiencing abnormally cool conditions. Cold winters in Japan and Primorye, over southern Alaska and western, central Canada. Cool summers over Southeast Africa, India and Southeast Asia. Warmer winters over the Southwest United States.