Cause and influence of El Nino and La Nina phenomena

The cause and influence of El Nino and La Nina;

I. Causes and effects of El Ni? o phenomenon

1, reason

El Nino phenomenon, also known as El Nino current, is a climatic phenomenon caused by the imbalance between the ocean and the atmosphere in the equatorial Pacific. Under normal circumstances, the monsoon air flow in the tropical Pacific moves from America to Asia, keeping the surface of the Pacific Ocean warm and bringing tropical rainfall around Indonesia.

However, this pattern is disturbed every 2-7 years, and the wind direction and ocean current are reversed. The heat flow in the surface of the Pacific Ocean turns eastward to America, and then takes away tropical rainfall, resulting in the so-called "El Ni? o phenomenon".

2. Influence

The impact of El Nino phenomenon is global. According to historical data, the global weather anomaly of 1972 was related to the particularly strong El Ni? o warm current that year. This year, the worst national drought occurred in China since the founding of the People's Republic of China. At the same time, serious floods have occurred in some countries and regions, and Africa has suffered a once-in-200-year catastrophic flood.

At the end of 1982, the El Ni? o warm current reappeared, and the sea water in the eastern Pacific near the equator increased abnormally, and the scope became larger and larger. Around Christmas, more than 1700 seabirds perched on Christmas Island disappeared. Then it rained cats and dogs and flooded. By 1983, El Nino had spread all over the world, and abnormal weather appeared continuously in America, Asia, Africa and Europe.

Second, the cause and influence of La Nina

1, reason

La Nina is the product of the interaction between tropical ocean and atmosphere. The motion of the ocean surface is mainly constrained by the sea surface wind. The existence of trade winds makes a lot of warm water blown to the equatorial western Pacific Ocean and blown away, mainly supplemented by cold water below the sea surface. The SST in the equatorial eastern Pacific is obviously lower than that in the western Pacific.

When the atmospheric circulation is abnormal and the trade winds are strengthened, the upwelling phenomenon of deep seawater in the equatorial eastern Pacific becomes more intense, which leads to the abnormally low sea surface temperature and the sinking of the equatorial eastern Pacific airflow.

In the western Pacific, the upward movement of airflow is more intensified, which is more conducive to the strengthening of trade winds, thus further aggravating the upwelling of cold water in the equatorial eastern Pacific, the sinking and rising of airflow in the western Pacific, and triggering the so-called La Nina phenomenon.

2. Influence

From the historical data, the frequency and intensity of this phenomenon are less than that of El Ni? o, and the duration is mostly longer. When La Nina appeared, there was more precipitation near the equator. On the contrary, the eastern and central parts of the equatorial Pacific are prone to drought. The impact of global climate events cannot be ignored.

The difference between El Nino and La Nina

1, expression form

El Nino phenomenon: The abnormal and continuous warming of seawater temperature in tropical seas in the eastern and central Pacific Ocean has changed the climate pattern of the whole world, resulting in drought in some areas and excessive rainfall in others.

La Nina phenomenon: It is a phenomenon that the sea surface temperature in the eastern and central equatorial Pacific Ocean is unusually cold in a large range (below 0.5℃ for six consecutive months), usually accompanied by El Ni? o, also known as "anti-El Ni? o".

2. Origin

El Nino phenomenon: It is found that the occurrence of El Nino event is related to the change of the earth's rotation speed. Since 1950s, the average acceleration distribution in the past 10 years has been destroyed by the earth's rotation speed, which fluctuated for 4-5 years. Some strong El Nino events occurred in the year when the earth's rotation speed changed greatly, especially in the year when the rotation slowed down.

La Nina phenomenon: It also has an impact on the climate. La Nina is the opposite of El Ni? o. With the disappearance of El Ni? o and the arrival of La Ni? a, the weather and climate disasters in many parts of the world will also change. Generally speaking, La Nina is not very gentle, and it is likely to bring disaster to many parts of the world.

3. Different impacts on climate.

La Nina's impact on the climate, strong cold waves and strong winds frequently appear in the north, but the rainfall continues to be less and the temperature remains high. El Nino's impact on climate is most significant in the equatorial Pacific. In the El Nino year, Indonesia, Australia, the South Asian subcontinent and northeastern Brazil all experienced drought, while it was rainy from the equatorial central Pacific to the west coast of South America.

El Nino will bring devastating effects, which may lead to floods in Latin America, droughts in Australia and crop failures in India.

4. The playing time is different

El Nino cycle: El Nino is a periodic natural phenomenon, which occurs about once every seven years. Through the study of global climate, scientists believe that El Nino is not an isolated natural phenomenon, but an aspect of global climate anomaly.

In normal years, the Pacific coast on the west coast of Peru is controlled by a cold ocean current, and there is a large natural fishing ground. Once there is a climate anomaly, the cold ocean current in the eastern Pacific will be replaced by the warm ocean current.