El Niño and La Niña are opposite phases of what is known as the El Niño-Southern Oscillation (ENSO) cycle.
The ENSO cycle is a scientific term that describes the fluctuations in temperature between the ocean and atmosphere in the east-central Equatorial Pacific (approximately between the International Date Line and 120 degrees West).
La Niña is sometimes referred to as the cold phase of ENSO and El Niño as the warm phase of ENSO. These deviations from normal surface temperatures can have large-scale impacts not only on ocean processes, but also on global weather and climate.
El Niño and La Niña episodes typically last nine to 12 months, but some prolonged events may last for years. While their frequency can be quite irregular, El Niño and La Niña events occur on average every two to seven years. Typically, El Niño occurs more frequently than La Niña.
El Niño means The Little Boy, or Christ Child in Spanish. El Niño was originally recognised by fishermen off the coast of South America in the 1600s, with the appearance of unusually warm water in the Pacific Ocean.
The name was chosen based on the time of year (around December) during which these warm waters events tended to occur.
The term El Niño refers to the large-scale ocean-atmosphere climate interaction linked to a periodic warming in sea surface temperatures across the central and east-central Equatorial Pacific. La Niña means The Little Girl in Spanish. La Niña is also sometimes called El Viejo, anti-El Niño, or simply “a cold event.”
La Niña episodes represent periods of below-average sea surface temperatures across the east-central Equatorial Pacific. Global climate La Niña impacts tend to be opposite those of El Niño impacts.
In the tropics, ocean temperature variations in La Niña also tend to be opposite those of El Niño.
El Nino in Tanzania
At the start of the year, the Tanzania Meteorological Agency (TMA) warned that what could be the biggest El Nino on record since the1997 one will this year hit East Africa.
The agency said this year’s El Nino will be one of the strongest and wettest El Ninos bringing heavy rains, floods and waterborne diseases.
The agency also predicted that there is a greater than 90 per cent chance of the weather phenomenon wreaking havoc until the short rains, with 80 per cent likelihood of lasting until April, this year.
With that warning, TMA underlined the need for the country to prepare for massive devastation “as record El Nino rains will start falling any time from now January to April”.
As predicted, unprecedented heavy rains have hit the country killing hundreds, displacing thousands and destroying millions worth of property and infrastructures.
El Niño and shift in rain patterns
El Niño is bringing an unprecedented shift in rain patterns. Now, NASA researchers are creating a visualization of these patterns to show exactly what they look like across the United States.
“During an El Niño, the precipitation averaged out over the entire globe doesn’t change that much, but there can be big changes to where it happens,” said George Huffman, one of the researchers, in a news release. “You end up with this interesting observation where you get both floods and droughts just by taking the usual precipitation pattern and doing a shift.”
El Niño is a natural weather phenomenon that occurs every two to seven years. It’s created through a shift in wind and ocean circulation; in normal, non-El Niño years, Pacific trade winds near the equator blow from east to west, moving warm surface water with them.
But during an El Niño, trade winds move from west to east from Southeast Asia to South America.
This moves warm water to the eastern tropical Pacific Ocean; the warm ocean water evaporates and falls as precipitation over nearby regions.
“Observing rainfall in an El Niño year is especially interesting because the prevailing precipitation patterns change, often in extreme ways,” said Dalia Krschbaum, one of the researchers, in a news release.
“Some areas become wetter. Some areas become drier. By seeing the whole globe, we are able to better understand how the precipitation is impacting different areas.”
The southern area of the United States, including central California, across Texas and to Florida is experiencing wetter-than-average conditions.
These conditions are expected to continue through June.
The findings reveal a bit more about this weather pattern, and show what kind of weather conditions we may face in the future.
El Nino destroying coral reefs
Corals are extremely ancient animals that evolved into modern reef-building forms over the last 25 million years. Coral reefs are unique (e.g. the largest structures on earth of biological origin) and complex systems.
Rivaling old growth forests in longevity of their ecological communities, well-developed reefs reflect thousands of years of history.
Global warming and the intense El Niño currently taking place could be prolonging the longest global coral die-off on record. The loss of corals from disease and heat stress due to record ocean temperatures could stretch well into 2017.
Coral bleaching occurs when corals are stressed by conditions such as high temperatures. The bleaching itself happens when corals expel their zooxanthellae, the symbiotic algae that live within their tissues.
Without this algae, the corals lose the ability to properly photosynthesize, which is a significant food source. This causes corals to become more vulnerable to disease and during a severe bleaching event, large swaths of reef-building corals die.
The first mass bleaching event occurred during the 1982-1983 El Niño. A global bleaching event then occurred in 1998 during another strong El Niño that was followed by a very strong La Niña, which brings warmer waters to places like Palau and Micronesia. Then, a second global bleaching event occurred in 2010 during a less powerful El Niño.
Now, it seems as if another bleaching event is underway. Scientists first observed the current global coral bleaching event beginning in mid-2014 when bleaching began in the western Pacific Ocean. In October 2015, as the current El Niño was still strengthening, researchers declared the third global bleaching event on record was underway.
Now, scientists have found that the bleaching event has persisted for 20 months, and could reach into 2017.
We’re seeing global bleaching again now,” said Mark Eakin, one of the researchers, in a news release. “The frequency of mass bleaching events are going up because of global warming.
We are hitting the corals, then we are hitting them again, and then again.”The findings show the importance of taking strides to help reefs. More specifically, conservation efforts are needed as warm temperatures persist and as corals die off.
El Niño and spread of dengue virus
El Niño may be causing the spread of the dengue virus. Scientists have found that this climate phenomenon has a significant role when it comes to the outbreak of haemorrhagic fevers.
The number of cases of dengue fever throughout the world is rising rapidly, propelling it to the status of a “re-emerging disease.”
Many countries in the intertropical zone see the number of cases of fever peak during the rainy season each year. But researchers wanted to see when and why these annual peaks turned into real outbreaks in 2010 and 2013 in Latin America and the Caribbean.
In this latest study, the researchers reviewed health reports from eight South-East Asian countries, spanning a period of 18 years.
The scientists developed models for dengue fever transmission across the entire region, and highlighted the correlation between the most serious epidemic waves and the abnormally high atmospheric temperatures associated with intense El Niño events.
Of particular note was a period of high incidence throughout South-East Asia from 1997 to 1998. This coincided with the most intense El Niño event of the 20th century.
The findings suggest that El Niño events may help increase the spread of haemorrhagic fevers. More specifically, the current El Niño event that’s taking place could mean an uptick in the number of cases of dengue fever.
This is particularly important to note when it comes to preventing the fever’s spread across country borders and throughout large populations.
Source: science world report
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