COLLEGE STATION - Lightning may not often strike twice in the same place, but it sure can hang out repeatedly in the same neighborhood. In Texas, that neighborhood is Houston, which Texas A&M University atmospheric scientists call the "lightning capital of the state."
Results of their lightning research, indicating that the high-energy stuff likes the city life, was originally published in Journal of Geophysical Research - Atmospheres, and an overview of that study is featured in the online July 1 issue of the prestigious science magazine, Nature.
The lightning study was co-authored by Texas A&M graduate student Scott Steiger, Texas A&M atmospheric scientist Richard Orville and Gary Huffines of Wright-Patterson Air Force Base in Ohio.
"We looked at 12 years of data and found that Houston gets more lightning than surrounding less metropolitan areas," Orville said. "The greater lightning frequency is not seasonal and may result from a combination of urban heat island effects and air pollution."
During the 12-year period from 1989 to 2000, the Houston area experienced 1.6 million cloud-to-ground lightning flashes, with 75 percent of them occurring in the summer months of June, July and August, 12 percent in December, January and February and the rest distributed throughout the remainder of the year. Refining of earlier methods enabled the researchers to study the concentration of lightning flashes in areas as small as 5 km.
Data analysis, including computer simulations, suggests that Houstons urban heat island effect causes clouds and thunderstorms. Urban areas heat up faster than agricultural lands because of the increased residential density and industrial activity, in Houstons case resulting in flow of cooler sea air inland toward the city center. As the cooler air rushes in, it forces the warmer air to rise, and as that air rises, moisture in it condenses, clouds form and thunderstorms occur. Further sea breezes then push the storms toward the northeast, with the observed lightning maximum over and to the northeast of the city.
Houstons air pollution may also be contributing to the frequent lightning. Soot particles emitted as pollutants from cars and power plants join other atmospheric aerosols originating from human activities and form the nuclei of cloud particles.
"Scientists believe that the charge separation mechanism of thunderstorms is determined by the size, concentration and phase of interacting cloud particles, in addition to temperature, vertical air velocity and liquid water content," Orville notes. "So the increased aerosol loading in urban areas may result in enhanced lightning activity and may be responsible for the observed high flash density in the Houston area."
Nationwide, lightning occurs when electric charges build up in clouds and then discharge to the ground. The polarity of lightning varies, with 90 percent of flashes bringing negative charges to ground and 10 percent, positive to ground. According to Orville, the positive discharges are more dangerous and often occur over forested areas, igniting destructive fires.
Lightning data is collected by a network of 106 sensors distributed over the 48 contiguous states. The sensors measure the electromagnetic fields from lightning discharges, much like static on a radio. Researchers use instruments to process recordings of the "static" and triangulate the location of the spot where the lightning strike occurred.
The lightning study was funded by the National Science Foundation, the National Oceanic and Atmospheric Administration and the Texas Air Research Center. An earlier publication in Geophysical Research Letters (May 2001) was co-authored by Orville, Steiger and Huffines, fellow Texas A&M faculty members John Nielsen-Gammon and Renyi Zhang and graduate students Brandon Ely and Stephen Phillips, along with Steve Allen and William Read of the National Weather Service, Houston-Galveston office. Lightning sensor data was obtained by the National Lightning Detection Network, operated by Global Atmospherics, Inc., of Tucson, Ariz.
"Sea breezes and storms have always converged over Houston, but 400 years ago it was just a natural effect, not influenced by people," Orville observed. "Now the 3 to 4 million persons who live in the Houston area, plus the 49 percent of the petroleum refining capacity in the U.S. located there create a powerful heat island effect, resulting in more intense cumulus cloud formation and more intense thunderstorms."
Judith White | EurekAlert
Water - as the underlying driver of the Earth’s carbon cycle
17.01.2017 | Max-Planck-Institut für Biogeochemie
Modeling magma to find copper
13.01.2017 | Université de Genève
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).
Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...
Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.
The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...
10.01.2017 | Event News
09.01.2017 | Event News
05.01.2017 | Event News
17.01.2017 | Earth Sciences
17.01.2017 | Materials Sciences
17.01.2017 | Architecture and Construction