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Global impacts of strong 2015 El Niño

People the world over are feeling, or soon will feel, the effects of the strongest El Niño event since 1997-98.

New satellite observations are beginning to show scientists the impact of this year’s El Niño on the distribution of rain, tropospheric ozone, and wildfires around the globe. NASA reports that the 2015 El Niño, currently unfolding in the eastern equatorial Pacific Ocean, is the strongest since 1997-98.

An El Niño, which is a reoccurring natural phenomenon, happens when sea surface temperatures in the equatorial Pacific Ocean warm up. The increased ocean surface temperatures influence air and moisture movement around the globe.

One big question about the current El Niño is whether it will bring significant rainfall to drought-plagued California. Researchers presented study results yesterday (December 15, 2015) at the American Geophysical Union meeting in San Francisco showing that atmospheric rivers – narrow corridors of concentrated moisture in the atmosphere and significant sources of rainfall – tend to intensify during El Niño events. These concentrated rain bands account for 40 percent of California’s water supply. Their results suggest the number of atmospheric rivers California receives will remain the same, at an average 10 per year, but thanks to this year’s strong El Niño, they will be stronger, warmer and wetter, which will likely will bring more precipitation to California and some relief for the drought.

Here’s a video of a 2014 atmospheric river:

NASA reports that due to this El Niño, tropospheric ozone, a pollutant and greenhouse gas, is seen decreasing over mid-latitude locations such as the United States.

New observation suggest the risk of fires across the tropics is showing signs of increasing. Jim Randerson, Earth system scientist at the University of California, Irvine, and his team analyzed wildfire burned area maps from satellite data to study how El Niño-driven effects change the distribution and severity of wildfires worldwide. During El Niños, the number and size of fires increases in tropical forests across Asia and South America. Randerson said:

The change in atmospheric dynamics shifts the rainfall. “So El Niño causes less rain to fall in many areas of the tropics, making forests more vulnerable to human-ignited fires.

Shown here is the monthly average of global burned area for August 2015, produced from data from the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Aqua satellite. Light blue indicates a small percentage of burned area, while red and orange indicate high percentages of burned area. Image credit: NASA

Shown here is the monthly average of global burned area for August 2015, produced from data from the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Aqua satellite. Light blue indicates a small percentage of burned area, while red and orange indicate high percentages of burned area. Image credit: NASA

Fires in tropical forests also accelerate carbon dioxide buildup in the atmosphere and reduce air quality. Indonesia, for example, has carbon-rich peatlands that ignite as soon as the rain stops, which is what happened this fall, Randerson said. Meanwhile, Southeast Asia, Central America, and the southern Amazon have very high fire risk for 2016. El Niño tends to reduce rainfall in their wet seasons, and less rain means drier vegetation and drier air, which make forests vulnerable to dry season burning.

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Bottom line: NASA reports that the 2015 El Niño, currently unfolding in the eastern equatorial Pacific Ocean, is the strongest since 1997-98.New satellite observations are beginning to show scientists the impact of this year’s El Niño on the distribution of rain, tropospheric ozone, and wildfires around the globe.

Read more from NASA

Eleanor Imster

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