Southern Oscillation
— Southern oscillation is the meteorological fluctuation between the Pacific Ocean and the Indian Ocean (Southern oscillation is the name ascribed to a see-saw pattern of meteorological changes that are often observed between the Pacific and the Indian Ocean.)' . According to this, whenever the air pressure in the Pacific Ocean is high, then the air pressure in the Indian Ocean is low. Conversely, when the air pressure is high in the Pacific Ocean, the air pressure in the Indian Ocean is high. The combined effect of El-Nino (EN) and Southern Oscillation is called Enso (ENSO).
The Southern Oscillation was invented by Sir Gilbert Walker in 1920. According to him, due to high and low air pressure in the Pacific and Indian Ocean, there is a vertical movement of air at the equator, in which the air in the area of low air pressure rises and in the area of high air pressure air descends. This is called the Walker Circulation. When there is low pressure in the Indian Ocean, the winds rise up and India receives good monsoon rains. When it is displaced towards the east (as happens during the time of El Nio) then there is less rainfall in India.
The Southern Oscillation Index (SOI) is used to measure the intensity of the Southern Oscillation. It indicates the difference in air pressure in the Pacific Ocean between Tahiti (17°45°N, 149°30°E) in French Polynesia and Australia's Port Darwin (12°30°N, 130°E) in the Indian Ocean. Is. The positive or negative values of the southern oscillations are determined by subtracting the air pressure at Port Darwin from the air pressure in Tahiti. positive Prices indicate good monsoon in India and negative prices indicate bad monsoon in India. In these events, there is a change in temperature by 0.4 in the East Pacific Ocean.
Effects of El-Nino
1. Indian Monsoon – A relationship has been established between El Nio and the Indian monsoon winds. Whenever there is an increase in temperature over the South Pacific Ocean and the effect of El-Nino increases, the monsoon weakens in India and the rainfall is less. But it has also been seen that even when there is no effect of El Nino, India receives less rainfall. In contrast, many El Nio years have also received substantial rainfall. Studies of the last one hundred years show that rainfall decreased in 43 years and 19 of them were El Nio years. In contrast, 6 El Nio years received substantial rainfall. So it is possible to say that while there is less rainfall in El-Nino years, not every El-Nino year is a time of less rainfall. 1877, 1899, 1918, 1972 and 1987 were El-Nino years and in these years the monsoon was very weak and the drought conditions were created due to less rainfall. 1987 was the worst drought of the twentieth century and was also a year of strong El Nio. Figure 23.18(A) shows that 1982, 1983 and 1987 were El-Nino years and the monsoon was very weak in these years. Figure 23.18 (B) shows the regions receiving less rainfall in the El-Nino years than the average rainfall for the years between 1901 and 1970. This shows that Gujarat, Maharashtra and the Western Coastal Plain receive 25% less rainfall in El Nio years. Apart from this, some parts of Maharashtra and Madhya Pradesh and western Karnataka receive less rainfall by 10-25 percent.
2. Effect of El-Nino on Peru- The biggest impact of El-Nino is on Peru as it originates near the Peruvian coast. Where El-Nino provides life to vegetation in the Atacama desert of this country, it causes immense damage in other parts of this country. Its disadvantages are many times more than its benefits. Due to this, the socio-economic and environmental system becomes unstable. The El Nino of 1982-83 killed 2000 people and caused a loss of wealth equivalent to US$ 13 billion. The heavy rain that gave life to the vegetation in the Atacama desert caused a large amount of landslides and terrible fences in the Andes mountainous region.
1. Indian Monsoon – A relationship has been established between El Nio and the Indian monsoon winds. Whenever there is an increase in temperature over the South Pacific Ocean and the effect of El-Nino increases, the monsoon weakens in India and the rainfall is less. But it has also been seen that even when there is no effect of El Nino, India receives less rainfall. In contrast, many El Nio years have also received substantial rainfall. Studies of the last one hundred years show that rainfall decreased in 43 years and 19 of them were El Nio years. In contrast, 6 El Nio years received substantial rainfall. So it is possible to say that while there is less rainfall in El-Nino years, not every El-Nino year is a time of less rainfall. 1877, 1899, 1918, 1972 and 1987 were El-Nino years and in these years the monsoon was very weak and the drought conditions were created due to less rainfall. 1987 was the worst drought of the twentieth century and was also a year of strong El Nio. Figure 23.18(A) shows that 1982, 1983 and 1987 were El-Nino years and the monsoon was very weak in these years. Figure 23.18 (B) shows the regions receiving less rainfall in the El-Nino years than the average rainfall for the years between 1901 and 1970. This shows that Gujarat, Maharashtra and the Western Coastal Plain receive 25% less rainfall in El Nio years. Apart from this, some parts of Maharashtra and Madhya Pradesh and western Karnataka receive less rainfall by 10-25 percent.
2. Effect of El-Nino on Peru- The biggest impact of El-Nino is on Peru as it originates near the Peruvian coast. Where El-Nino provides life to vegetation in the Atacama desert of this country, it causes immense damage in other parts of this country. Its disadvantages are many times more than its benefits. Due to this, the socio-economic and environmental system becomes unstable. The El Nino of 1982-83 killed 2000 people and caused a loss of wealth equivalent to US$ 13 billion. The heavy rain that gave life to the vegetation in the Atacama desert caused a large amount of landslides and terrible fences in the Andes mountainous region.
In 1983, a place called Guayaquil in Peru received 20 times more rainfall than normal. Some rivers started flowing 1000 times more water than normal. Strong winds in Ecuador caused property damage worth US$400 million.
3. Weather of North America and El-Nino- El-Nino also has an effect on the weather of North America. For example, in the United States, the warmer-than-normal weather in 1983-84 is believed to be El-Nino. At that time, due to El Nio in Alaska and Northwest Canada, the temperature remained very high.
4. Impact on Agriculture- El Nino in India causes less rainfall and adversely affects agricultural production. In other parts of the world also there are examples of drought due to El Nino. In 1982–1983 and 1997–98, Australia, Indonesia, Mexico, the Philippines and South Africa experienced severe droughts, largely attributed to El Nio. This caused a loss of $ 100 million in South Africa, $ 600 million in Mexico, $ 500 million in Indonesia and $ 450 million in the Philippines.
5. Epidemics- El-Nino causes less than normal rainfall at some places and above normal at some places. In both these situations, drought and flood situation arise respectively. In the event of drought, there is a famine and there is a shortage of food. A large number of people suffer from malnutrition. In the event of a flood, the water gets filled on which mosquitoes breed. These mosquitoes spread dreadful diseases like malaria, dengue, jaundice, encephalitis, dysentery, cholera etc. 1982 The 1983 El Nio event caused widespread malaria in Colombia, Peru, India and Sri Lanka. Due to the high rainfall in the desert part of Peru, deer mice spread rapidly, which infects the disease in humans.
6. Loss of fauna- El Nino provides life to the vegetation here by raining in the desert, while it damages the marine life on a large scale. Near the coast of Peru and Ecuador, there is a small salt fish called anchovy. This fish thrives in cold and upwelling water rising up because of the abundance of nutritious elements in this water. These nutrients are fed by plankton which provide food for the fish. Cold water rises during an El-Nino event, but it is confined to the upper level at a depth of 125-150 meters. Due to this the plankton do not get proper nutrition and their quantity is reduced. As a result, even the buffalo do not get proper diet. In such a situation, the fish either migrate to other areas, or die there. Birds who use fish as food also suffer and do not get enough guana from them. This feces is the basic foundation for the fertilizer industry. Therefore, during the El-Nino event, the supply of manure gets reduced and agriculture suffers huge losses. As a result, fisheries and agriculture businesses have to face great difficulties.
During the El-Nino event, the coral reefs are also heavily damaged by the excess of warm water in the upper layer of the ocean. During the El Nio event of 1982–83, there was widespread destruction of coral reefs in Colombia, Costa Rica, Panama, and the Galapagos Islands, 50 to 97 percent of coral reefs in the Galapagos Islands were destroyed. During the El Nio event of 1997-98 .
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