Posted: February 13, 2015 in Uncategorized

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UNIVERSITY OF IOWA – Original Study:


Tornadoes in the Southeast and Central U.S. are episodically accompanied by smoke from biomass burning in Central America. Analysis of the 27 April 2011 historical tornado outbreak shows that adding smoke to an environment already conducive to severe thunderstorm development can increase the likelihood of significant tornado occurrence. Numerical experiments indicate that the presence of smoke during this event leads to optical thickening of shallow clouds while soot within the smoke enhances the capping inversion through radiation absorption. The smoke effects are consistent with measurements of clouds and radiation before and during the outbreak. These effects result in lower cloud bases and stronger low-level wind shear in the warm sector of the extra-tropical cyclone generating the outbreak; two indicators of higher probability of tornado genesis and tornado intensity and longevity. These mechanisms may contribute to tornado modulation by aerosols, highlighting the need to consider aerosol feedbacks in numerical severe weather forecasting.

Posted by Gary Galluzzo-Iowa on February 13, 2015

You are free to share this article under the Attribution 4.0 International license.

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.

“Our model predicted storm paths with 100-kilometer—50-mile—accuracy four to five days ahead of landfall for Hurricane Sandy,” says Fuqing Zhang.

“We also had accurate predictions of Sandy’s intensity.” (Credit: NOAA/NASA GOES Project)
Penn State

Hurricane tracker predicts storm’s strength and path

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


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