The oceanic-atmospheric phenomenon wherein waters in the equatorial Pacific warm up abnormally due to the weakening of trade winds is termed as El Nino.
El Nino re-emerges after a gap of about two to five years in the Pacific Ocean and its effects last for about 12 months on an average.
El Nino is known to cause warming of the sea surface temperatures (SST), which in turn affects wind patterns. Such an event is usually characterized by extreme weather events including floods and droughts in different parts of the world. However, few places across the globe also benefit by El Nino.
Worldwide, people are already feeling, or will soon feel, the effects of the strongest El Nino event since the year 1997-98. The latest satellite observations by NASA are showing its impact on the distribution of rain, wildfires and tropospheric ozone.
This El Nino is leading to a decrease of tropospheric ozone, pollutant and greenhouse gas, over mid-latitude locations including the United States. Also, the risk of fires is increasing across the tropical areas.
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An El-Nino year is often seen as a year of deficit Monsoon rain in India but it also has some other worldwide impacts. These have been listed below.
1. El Nino is known to intensify atmospheric rivers, which are significant sources of rainfall. Accordingly, this year's strong El Nino is likely to bring more precipitation to the drought-stricken California.
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2. El Nino increases the sea surface temperatures, which in turn shifts rain patterns and affects the temperature of the air above the ocean. This alters the way air masses circulate air around the planet, affecting the distribution of tropospheric ozone around the planet.
3. Previously we believed that El Nino events lead to strong changes in ozone layer in the tropics. But recent observations, using satellite data combined with a computer model, suggest that a smaller but still significant effect occurs in the mid-latitudes as well. This research has been conducted by Mark Olsen, an atmospheric research scientist at Morgan State University in Baltimore and NASA's Goddard Space Flight Center in Greenbelt, Maryland.
4. Jim Randerson, Earth system scientist at the University of California, Irvine, analyzed wildfire burned area maps from satellite data along with his team to study how El Nino leads to change in the distribution and severity of wildfires worldwide.
It is to be noted that the number and size of wildfires increases in tropical forests across Asia and South America during the El Nino years. This is because El Nino brings less rainfall over many areas situated in the tropics, making forests more vulnerable to human-ignited fires.
5. Bushfires in tropical forests accelerate carbon dioxide buildup in the atmosphere, significantly reducing air quality. For instance, Indonesia has carbon-rich peat lands that tend to ignite as soon as the rain stops. This was one of the reasons for the extensive peat fires in Indonesia this fall.
6. Southeast Asia, Central America and the southern Amazon generally bear high fire risk for 2016. This is because El Nino had reduced rainfall in their wet seasons.
7. El Nino events are generally associated with physical and biological changes in our oceans.
8. In the Northern Hemisphere, tropical and warm water species move northwards, thereby extending their range. Cold water species move north or into deeper waters, thereby restricting their range. Similarly, surface-oriented, schooling fish often disperse and move into deeper waters. Fishes that remain in an affected region experience reduced growth, reproduction, and survival.
This El Nino has also been held responsible for back to back droughts in India.
Click here to read the story, Southwest Monsoon: El Nino and MJO ride over IOD
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