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Scientists say smoke particles likely played a role in a deadly tornado outbreak on April 27, 2011.

The weather event produced 122 tornadoes, resulted in 313 deaths across the southeastern United States, and is considered the most severe event of its kind since 1950.

The smoke was the result of spring agricultural land-clearing fires in Central America—transported across the Gulf of Mexico and encountering tornado conditions already in process in the United States.

Researchers at the University of Iowa say smoke lowered the base of the clouds and increased wind shear, defined as wind speed variations with respect to altitude. Together, those two conditions increased the likelihood of more severe tornadoes, according to computer simulations.

“These results are of great importance, as it is the first study to show smoke influence on tornado severity in a real case scenario. Also, severe weather prediction centers do not include atmospheric particles and their effects in their models, and we show that they should at least consider it,” says Gregory Carmichael, professor of chemical and biochemical engineering and co-lead author of the study published in the journal Geophysical Research Letters.

“We show the smoke influence for one tornado outbreak, so in the future we will analyze smoke effects for other outbreaks on the record to see if similar impacts are found and under which conditions they occur,” says Pablo Saide, a postdoctoral fellow.

“We also plan to work along with model developers and institutions in charge of forecasting to move forward in the implementation, testing, and incorporation of these effects on operational weather prediction models.”

The study was coauthored by researchers from the National Oceanic and Atmospheric Administration Satellite and Information Service Center for Satellite Applications and Research, the University of Wisconsin-Madison, and NASA.

Grants from NASA, the US Environmental Protection Agency, National Institutes of Health, National Oceanic and Atmospheric Administration, and the Fulbright-CONICYT scholarship program in Chile funded the project.

Source: University of Iowa