However, Peruvian fishermen experience a recurring natural phenomenon during Christmas emphasized by paucity in fishing and high precipitation. They called this El Nino, Spanish for The Christ Child or an infant boy.
They also experience an entire reversal of events with a glut in fishing and drought inland. They termed this phenomenon La Nina, an infant girl.
Global Impact
El Nino and La Nina are phenomenon that occurs in the tropical Pacific, but with the energy content of a million atomic bombs, it has a cataclysmic effect on the global weather pattern.
Our planet does not receive a uniform solar insolation - tropics receiving the most heat and the poles receiving the least. Earth has developed an intricate mechanism to deal with this differential heating. There is a complex coordination between our oceans and the atmosphere to make our planet a sustainable place to live on.
Extreme weather events – drought in India and China, ice storm in the northern US can be linked to a strong El Nino whereas strengthening tropical storm in the Atlantic could be due to a knock-on effect of La Nina.
The impact this natural phenomenon in a remote part of the globe has on our entire planet is profound. The loss in lives and economic havoc created by El Nino has made it important for us to better understand its excruciating presage and take proactive measures to minimize its impact on our society.
ENSO
Southern Oscillation is the atmospheric phenomenon of the see-saw pattern of reversing surface air pressure, temperature and precipitation between the eastern and western tropical Pacific.
El Nino is the oceanic phenomenon of the flip-flop of location and depth of warm pools of water in the tropical Pacific.
The atmospheric and oceanic phenomenon is collectively called El Nino Southern Oscillation (ENSO).
When and How Often?
Based on a study, from the period of 1950 to 1997, El Nino conditions were present for 31%, La Nina for 23% and La Nada (Spanish: nothing) for 46% of the time. Although, there is no concrete number, El Nino is believed to occur every 2-7 years and each occurrence lasting 1-2 years.
La Nada
In normal scenario, Trade Winds blow from the east to the west in the tropics. These winds induce surface currents resulting in the sea surface to be 50cm higher in Indonesia than Ecuador. Sea temperature is usually 8°C higher in Indonesia as compared to Peru in the East Pacific. The high temperature in the waters of the West Pacific induces moisture laden wind to precipitate and result in higher rainfall. The East Pacific is relatively dry.
El Nino and La Nina
|
|
El Nino |
La Nina |
|
Cause |
Weakening of the Trade Winds. A surge of hot moisture laden wind blowing from the West Pacific to the East Pacific takes the charge. |
Strengthening of the Trade Winds. |
|
Trigger |
If the temperature of the West Tropical Pacific is 0.5°C above long term average, it is officially declared as El Nino |
If the temperature of the West Tropical Pacific is 0.5°C below the long term average, it is officially declared as La Nina |
|
Mechanism |
High Atmospheric Pressure in the West Low Atmospheric Pressure in the East
The pool of warm water from the West Pacific moves towards Peru driven by the hot moisture laden wind. This wind brings thunderstorm and
rainfall to the South American countries. Eastward moving warm pool of water stalls upwelling in Peru and leads to the decline in fisheries. |
Low Atmospheric Pressure in the West High Atmospheric Pressure in the East The pool of cold water from the East Pacific (brought to the equator by the Peruvian Current) move towards Indonesia driven by the strong Trade Winds. It gets warm and saturated during its journey and brings high precipitation to the West Tropical Pacific. When this pool gets too large, it begins to slosh back eastward. Kelvin Waves which can be as long as 1000km, travels along the equator and carries warm west tropical water to the east. When it hits the South American coast, it generates long lived Rossby Waves. |
|
Effects |
Drought in usually wet Indonesia, Philippines, Australia and India. Heavy rainfall in Peru, Ecuador, Brazil, Argentina and Southern USA. Due to decrease in the sea level in Western Pacific, many corals in Indonesia and Australia die due to Coral Bleaching Decline in fisheries in Peru |
Drought in South American countries. Heavy rainfall in Indonesia, Philippines, Australia and India. Devastating effects in the Atlantic Coast of USA bringing thunderstorms and hurricanes. Increased fisheries in Peru |
|
Occurrence |
Summer of Southern Hemisphere [Dec-Feb] May last 1-2 years |
Summer of Southern Hemisphere [Dec-Feb] May last 1-2 years |
2014: El Nino or La Nada?
2014 is predicted to be an El Nino year. The governments in several countries are taking measures to prepare themselves for its consequences. Indian government had taken proactive measures to tackle food inflation which would have resulted due to weak monsoon and failed agriculture.
The first signs of an El Nino came in January 2014, when the Trade Winds suddenly weakened, and a burst of winds from the west triggered a slow surge of warm water into the eastern equatorial Pacific. But, the atmosphere did not coordinate with the ocean to substantiate the heat content of the ocean. The El Nino eventually stalled by the end of July.
NOAA still believes that there is a 65% chance of a weak to moderate El Nino to form by the end of this year.
Notes
- A flourishing coral has a symbiotic relation with algae it lives with. Algae give oxygen and organic compounds to the coral. Coral, in turn, gives shelter to the algae. But, when the temperature of the ocean exceeds 28°C, coral expels the algae that thrive within, leading to a loss of pigmentation and its eventual death. This is called Coral Bleaching.
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