The presented chapter attempts to explain some specific atmospheric phenomena such as Walker transmission, El Niño, La Niña, El Niño Modocci, La Niña Modocci, ENSO etc. Simultaneously micro-climates, applied climatology and their effects on human life have been described.
El Nino
El Nino is a Spanish word that literally means "The Little Boy" or "Christ Child", as this stream originates around Christmas. El Niño is a complex weather system occurring every 5 to 10 years. This system consists of oceanic and atmospheric phenomena. This causes climatic anomalies to be reversed by global seasonal conditions. Due to this, droughts, floods and extreme seasonal conditions arise in different parts of the world.
Under normal conditions, the waters of the East Pacific Ocean (near Peru and Ikkador) are cold and shallow and the waters of the Western Pacific Ocean (Indonesia and Western Australia) are warm and deep. In this case, the cold waters of Peru flow along the Peruvian coast towards the equator, known as the Humboldt Stream. Also prevalent, sea water is carried far away from the coast by the winds. With the removal of this surface water, the cold water comes up from the surface as a result of the discharge of the cold water.
Cold Water Upwelling
The surface water is pushed away from the coast by the winds flowing parallel to the shoreline and the water coming down takes the place of this water. The arrival of this cold water from the sea to the surface is called levitation.
At the time of solubilization, there is abundant nutrient in the water coming from the depths of the sea to the surface, which helps in the growth of seaweeds and phytoplankton. These phytoplankton serve as a basic source of energy for animals at high levels in the food chain, such as fish, marine mammals, sea birds, etc. For this reason, many coastal elevation systems, such as the West Coast of the United States, are one of the world's most productive coastal ecosystems and are also important in fisheries terms.
Apart from the above process of cold water stirring, there are other types of stirrings
It is known that the year in which the El Niño is occurring, the rainfall in the eastern tropical part of the eastern Pacific Ocean increases by 4 to 6 times on average, while in the western Pacific Ocean, there is a drought situation that causes Indonesia, India, Bangladesh etc. are hit by drought. Due to El Nino, the southwest monsoon weakens and the lack of rainfall in India increases the chances of drought. The 1997–98 horrific fire in Indonesia's forests has been described as a byproduct of the drought caused by El Niño.
During El Niño, trading winds weaken from their actual position. This weak surface helps to strengthen the warm equatorial current and helps to replace the cold Peruvian current that flows along the coast of South America. This stream flows the warm waters of the West Pacific Ocean towards the Central and East Pacific Ocean. Thus it also increases the sea surface temperature of the Pacific Ocean.
- Offshore winds
- Oceanic ventilation
- Changes in oceanic coastal geometry
In El Niño year:
In certain years the Peru or Humboldt water stream is replaced by El Niño and the eastern Pacific Ocean is warmer and the Western Pacific Ocean becomes relatively colder. This cold water rises 3 to 4 degrees Celsius above normal near El Parino, the predominant El Niño, causing excessive rainfall through convection in these areas. |
| General Conditions in the Tropical Pacific & El Nino Conditions in the Tropical Pacific |
Effect of El Nino
Biological destruction
Due to El Nino, due to excessive rainfall, the coastal desert sites become green, but the marine part: biological destruction. It is known that the coastal oceanic island of Peru is the most productive in the world for ocean organisms, because in normal conditions, there is an upward flow of cold water containing nutrients from the ocean at the bottom. ) Is helpful in growth. When El Nino is activated, this process stops, due to which there is lack of nutrients. This leads to a major reduction in primary productivity and disrupts the seafood chain. As a result, ocean biodiversity is affected.Excess of rain and effect on Indian monsoon
Due to the El Niño effect, some inland areas of South America, generally considered dry, receive heavy rainfall. In general, this desert region becomes green in nature and relatively increase in agricultural productivity is observed.It is known that the year in which the El Niño is occurring, the rainfall in the eastern tropical part of the eastern Pacific Ocean increases by 4 to 6 times on average, while in the western Pacific Ocean, there is a drought situation that causes Indonesia, India, Bangladesh etc. are hit by drought. Due to El Nino, the southwest monsoon weakens and the lack of rainfall in India increases the chances of drought. The 1997–98 horrific fire in Indonesia's forests has been described as a byproduct of the drought caused by El Niño.
Walker transmission or Circulation
Walker transmission is the east – west circulation occurring in the upper atmosphere of the tropical Pacific. A vascular cell is formed as a result of high pressure gradient. This pressure gradient arises from high pressure over the eastern Pacific and low pressure near Indonesia.
Eastern trading winds are part of the low-level transmission of the walker cell. Commercial winds are generally humid and humid in the Indonesian region. Here these humid winds normally flow from very hot sea area and reach the Hoker high atmospheric level. Due to these ascending winds, low pressure area, constant rain cloud and rain area are formed here. On the other hand, the winds propagating towards the east descend into the eastern Pacific Ocean. Due to these descending winds, high pressure and dry conditions are created here. Thus the walker cell is completed.
The walker transmission weakens or even reverses during El Niño. The surrounding ocean area of Australia gets colder, causing high air pressure and, therefore, less rainfall in the region. Conversely, due to El Niño in the eastern Pacific, warming sea water creates an area of low air pressure. At this stage, westerly winds begin to move over the western equatorial and parts of the Central Pacific, which is usually the eastern trading windmill.
The characteristics of walker transmission are largely determined by the combination between the tropical atmosphere and the oceans. Its intensity fluctuates along with the southern oscillation.
The characteristics of walker transmission are largely determined by the combination between the tropical atmosphere and the oceans. Its intensity fluctuates along with the southern oscillation.
Impact of Walker Transmission on Global Climate:
Atmospheric effects related to Walker transmission fluctuations are found around tropical and subtropical regions of the Pacific Rim. Walker transmission largely controls the exchange of motion, heat and water vapor occurring in tropical regions. Thus it plays an important role in the balance of atmospheric energy in equatorial regions as well as determining the characteristics of weather and climate in tropical regions.
Equatorial Countercurrent
It is a surface stream flowing between the northern and southern equatorial currents which flows from west to east slope. The accumulation of water in the western part of the ocean due to commercial winds creates a general gradient gradient (in water) from west to east direction, due to which a stream of water starts to flow eastward with the help of gradient. is. It is a reflection of the Pacific Ocean that increases its effectiveness by increasing El Nino's effectiveness.During El Niño, trading winds weaken from their actual position. This weak surface helps to strengthen the warm equatorial current and helps to replace the cold Peruvian current that flows along the coast of South America. This stream flows the warm waters of the West Pacific Ocean towards the Central and East Pacific Ocean. Thus it also increases the sea surface temperature of the Pacific Ocean.
El Niño Southern Oscillation (ENSO)
- Two phenomena are included under ENSO: The first is mainly oceanography known as El Niño. The second phenomenon is atmospheric called Southern oscillation.
- During El Niño, low dow is formed over a large part of the southeastern Pacific, while high pressure occurs near Indonesia and northern Australia, located in the Western Pacific. At the end of the El Niño event, the atmospheric pressure difference between these two regions changes again to its opposite position. This C-S pattern of atmospheric pressure between the eastern and western Pacific is known as the "southern oscillation".
- The intensity of the southern oscillation is represented by the Southern Oscillation Index (SOI). The intensity of SOI is measured by the difference in pressure fluctuations between Tahiti, French Polynesia, Darwin and Australia. Under the positive value of SOI, the pressure in the Indian Ocean region is lower in the winter season and higher in the Pacific Ocean region. This makes the southwest monsoon common. In contrast, the pressure in the region is found to be higher in the Indian Ocean region during negative values. This makes the monsoon weak. The negative value is directly related to the development of El Niño, its combined effect is known as ENSO phenomenon.
- ENSO helps in the transfer of heat from low latitudes to high latitudes. It is considered as an essential mechanism to sustain long-term global climatic stability.
- Oxygen dissolved in seawater begins to decrease due to the long-lasting ENSO phenomenon. As a result, hydrogen-sulfide and other gases are produced. These gases are responsible for coral wall bleaching and also damage the lead paint of ships.
- The most important aspect of the ENSO phenomenon is that it causes changes in the form of rainfall all over the world.
