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
Gas hydrate research: Advanced knowledge and new technologies
23.03.2018 | Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum GFZ
New technologies and computing power to help strengthen population data
22.03.2018 | University of Southampton
Satellites in near-Earth orbit are at risk due to the steady increase in space debris. But their mission in the areas of telecommunications, navigation or weather forecasts is essential for society. Fraunhofer FHR therefore develops radar-based systems which allow the detection, tracking and cataloging of even the smallest particles of debris. Satellite operators who have access to our data are in a better position to plan evasive maneuvers and prevent destructive collisions. From April, 25-29 2018, Fraunhofer FHR and its partners will exhibit the complementary radar systems TIRA and GESTRA as well as the latest radar techniques for space observation across three stands at the ILA Berlin.
The "traffic situation" in space is very tense: the Earth is currently being orbited not only by countless satellites but also by a large volume of space...
An international team of researchers has discovered a new anti-cancer protein. The protein, called LHPP, prevents the uncontrolled proliferation of cancer cells in the liver. The researchers led by Prof. Michael N. Hall from the Biozentrum, University of Basel, report in “Nature” that LHPP can also serve as a biomarker for the diagnosis and prognosis of liver cancer.
The incidence of liver cancer, also known as hepatocellular carcinoma, is steadily increasing. In the last twenty years, the number of cases has almost doubled...
In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.
Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...
Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.
They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...
A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...
23.03.2018 | Event News
19.03.2018 | Event News
16.03.2018 | Event News
23.03.2018 | Materials Sciences
23.03.2018 | Agricultural and Forestry Science
23.03.2018 | Physics and Astronomy