It was just a week after the tornado. He was between the two cities, in the rough country of the southern Appalachians about 20 miles northeast of Tuscaloosa. He said it's terrain that's "beyond hilly." It's covered by dense forest and clogged by high brush that's tough to walk through. A hike of about 100 yards sometimes took as long as 45 minutes.
It was a perfect place for Karstens - a doctoral student from Atlantic who's studying under the direction of Bill Gallus, a professor of geological and atmospheric sciences - to study the effects of complex terrain on the structure of a tornado.
The study is part of a larger Iowa State research program led by Partha Sarkar, a professor of aerospace engineering and director of the university's Wind Simulation and Testing Laboratory. The lab includes several conventional wind tunnels and a Tornado/Microburst Simulator that has been fully functional since 2005. The Tornado/Microburst Simulator has helped researchers attract about $2.3 million from the National Oceanic and Atmospheric Administration and $580,000 from the National Science Foundation to study the impacts of tornado and microburst winds near the ground and their effects on buildings and other structures. One goal is to develop innovative ways to make structures, particularly low-rise buildings, stand up to tornadoes, hurricanes, gust fronts and microbursts from thunderstorms.
Iowa State's tornado research teams have included Sarkar; Gallus; Hui Hu and Vinay Dayal, associate professors of aerospace engineering; Fred Haan, an associate professor of mechanical engineering at the Rose-Hulman Institute of Technology in Terre Haute, Ind., and former aerospace engineering faculty member at Iowa State; Sri Sritharan, professor of civil, construction and environmental engineering; and Gene Takle, professor of agronomy and geological and atmospheric sciences.
"We've learned a lot in terms of the distribution of wind and in terms of the interaction of wind with structures and terrain," said Sarkar.
Sarkar said the researchers have found, for example, that when a tornado blows over rough terrain - forests or densely built cities - the structure of the tornado changes. The swirl and maximum rotational speed of the tornado decrease and the vortex spins tighter with a smaller core.
Karstens took that study further by looking at what happens to a tornado when it hits complex terrain such as cliffs, slopes and valleys. That's why Karstens joined other researchers studying the damage caused by the Tuscaloosa-Birmingham tornado.
The researchers looked at the damage to homes and buildings in the cities - part of their work to develop structures that can withstand high winds. Then Karstens headed for the hills to study the damage there.
He hiked to the storm path and noted damage on the ground and in the trees. He looked for signs that the terrain had disrupted the tornado as it moved up and down the steep slopes. He hiked to the top of valleys so he could take pictures of the damage below.
Back in Ames, he also studied aerial photos of the storm damage. That's when he noticed that trees along valleys far from the tornado path were damaged by high winds.
Karstens returned to the area last January for a second and closer look at specific locations he had identified. He looked at how the damage changed as the storm moved up and over the low mountains. He studied how root and soil conditions could have influenced the storm damage. And he explored side valleys perpendicular and to the left of the tornado's path to see the storm damage he noticed on the aerial photographs.
"It was very beneficial to go," Karstens said. "By physically observing the damage I could identify the situation, use some intuition and interpret what happened. That can lead to new ideas and thoughts."
One thought he took back to campus is that the perpendicular valleys provided a channel for the high winds and kept them going far from the actual tornado.
To test the theory, Karstens built a 32-foot by 20-foot 3-D foam replica of a 2-mile by 3-mile section of the same Alabama countryside he explored on foot. Then he ran Iowa State's Tornado/Microburst Simulator over the model terrain, taking wind readings inside the various valleys.
Karstens, who has accepted a research job at the Cooperative Institute for Mesoscale Meteorological Studies in Norman, Okla., is still analyzing the data. But he thinks he's onto something new.
"For meteorology, this can add another piece to the puzzle," he said. "It can help us understand the near-surface flow of winds in tornadoes."
Christopher Karstens | EurekAlert!
Greenland ice flow likely to speed up: New data assert glaciers move over sediment, which gets more slippery as it gets wetter
17.08.2017 | Swansea University
Climate change: In their old age, trees still accumulate large quantities of carbon
17.08.2017 | Universität Hamburg
Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.
As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...
Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.
Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...
For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.
While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...
An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.
The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...
A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.
Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...
16.08.2017 | Event News
04.08.2017 | Event News
26.07.2017 | Event News
18.08.2017 | Life Sciences
18.08.2017 | Physics and Astronomy
18.08.2017 | Materials Sciences