The causes of El Nino phenomenon

When the southeast wind blowing near the equator in the southern hemisphere weakens, the cold water flooding in the Pacific will be reduced or stopped, which will lead to the abnormal warming of seawater temperature in a large range, and the traditional equatorial ocean current and atmospheric circulation will also be abnormal, resulting in abnormal precipitation in some areas along the Pacific coast and severe drought in some areas.

2. Earth's rotation

It is found that the occurrence of El Nino event is related to the change of the earth's rotation speed, and the short-term change of the earth's rotation speed is negatively correlated with the change of SST in the equatorial eastern Pacific, that is, when the earth's rotation speed accelerates in the short term, the SST in the equatorial eastern Pacific decreases; On the contrary, when the earth's rotation rate slows down for a short time, the SST in the equatorial eastern Pacific increases. This shows that the slow rotation of the earth may be the main reason for the formation of El Ni? o phenomenon.

When the earth's rotation slows down, the "braking effect" makes the atmosphere and seawater in the equatorial belt gain an eastward inertia, the equatorial ocean current and trade winds weaken, the warm water in the western Pacific flows eastward, and the cold water in the eastern Pacific is blocked, resulting in the El Ni? o phenomenon that the accumulation of warm water causes the seawater to warm and the sea surface to rise.

Extended data:

First, the judgment conditions

The main conditions for judging El Ni? o phenomenon are pressure change, wind direction change, sea surface temperature change, sea level height change, earthquakes and volcanic activities around the Pacific Ocean, abnormal reduction of sea ice on the Antarctic Peninsula, multiple solar eclipses at the poles and abnormal droughts and floods. It is generally believed that the El Ni? o phenomenon occurred when the sea surface temperature in the equatorial eastern Pacific Ocean was higher than the average of 0.5 degrees Celsius for six consecutive months.

Second, the impact

The most certain impact is that El Nino events lead to a significant increase in global precipitation compared with normal years. This has led to frequent floods in the central and eastern Pacific Ocean and Pacific coastal countries in South America, while severe droughts in India, Indonesia and Australia have affected many crops in the world.

1April 1982 to1July 1983, the El Ni? o phenomenon was the worst in centuries. The water surface temperature in the eastern and central Pacific Ocean is about 4-5℃ higher than normal, resulting in 1300 ~ 1500 deaths and economic losses of nearly 100 billion US dollars.

The El Nino phenomenon in 1986 ~ 1987 made the surface water temperature in the equatorial Middle East Pacific about 2℃ higher than the annual average temperature. At the same time, the atmospheric circulation in tropical areas is also abnormal, and the weather in tropical areas is also abnormal.

Heavy rains hit northern and central Peru in South America; The flood of the Amazon River in Colombia has caused the riverbank to burst many times; There is little rain and drought in the northeast of Brazil and hot in the west; Rainfall in eastern Australia and coastal areas has decreased significantly; There is little rain and drought in South China, South Asia and North Africa.

Baidu encyclopedia-El Nino phenomenon