New model predicts global warming will intensify storms

Washington, July 9 : A new mathematical model indicates that dust devils, water spouts, tornadoes, hurricanes and cyclones are all born of the same mechanism and will intensify as climate change warms the Earth's surface.

The new equation, developed by University of Michigan atmospheric and planetary scientist Nilton Renno, could allow scientists to more accurately calculate the maximum expected intensity of a spiraling storm based on the depth of the troposphere and the temperature and humidity of the air in the storm's path.

The troposphere is the lowest layer of Earth's atmosphere.

According to Renno, this equation improves upon current methods because it takes into account the energy feeding the storm system and the full measure of friction slowing it down.

Current thermodynamic models make assumptions about these variables, rather than include actual quantities.

"This model allows us to relate changes in storms' intensity to environmental conditions," said Renno.

"It shows us that climate change could lead to increases in how efficient convective vortices are and how much energy they transform into wind. Fueled by warmer and moister air, there will be stronger and deeper storms in the future that reach higher into the atmosphere," he added.

Renno and research scientist Natalia Andronova used the model to quantify how intense they expect storms to get based on current climate predictions.

For every 3.6 degrees Fahrenheit that the Earth's surface temperature warms, the intensity of storms could increase by at least a few percent. For an intense storm, that could translate into a 10 percent increase in destructive power.

Renno's work bolsters studies by others who say hurricanes have grown stronger over the past 50 years as sea surface temperatures have risen.

This new model also helps explain the formation of spiral bands and wall clouds, the first clouds that descend during a tornado. It's clear now that they are the result of a pressure drop where the airspeed has increased.

According to Renno, unifying convective vortices from dust devils to cyclones will help scientists better understand them.

"This is the first thermodynamic model that unifies all these vortices," he said. "When you unify them, you can see the big picture and you can really understand what makes them form and change," he added.

ANI