Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Mountain winds may create atmospheric hotspots

19.10.2005


Rapidly fluctuating wind gusts blowing over mountains and hills can create "hotspots" high in the atmosphere and significantly affect regional air temperatures. A research paper to be published this month in the Journal of Geophysical Research-Space Physics reports that the actions of such winds can create high-frequency acoustic waves and could stimulate a 1000-Kelvin [1,000-degree Celsius; 2,000-degree Fahrenheit]spike in a short period of time in the thermosphere, at an altitude of 200-300 kilometers [100-200 miles]. Such exceptional temperature increases would require continuous waves, and the heating rate would likely be diminished with intermittent winds.



Richard Walterscheid and Michael Hickey used a theoretical model of the interaction between rough terrain and wind eddies to suggest that high winds may represent a previously unknown source of acoustic waves in the environment. Ocean waves and earthquakes are known to produce similar waves, which strengthen as they propagate higher in the atmosphere. The authors speculate that the waves can heat the atmosphere at prodigious rates and could account for a large part of the unusual and unexplained high-altitude background heating seen above the mountainous landscape in parts of South America.

"We show that that the acoustic waves generated by gusty flow over rough terrain might be a significant source of heating in the upper atmosphere," Hickey says. "These mysterious so-called ’hotspots’ observed above the Andes Mountains could be explained by such acoustic wave heating."


Previous observations near the Andes Mountains in Peru had found that the atmosphere directly above some peaks was approximately 100 Kelvin [100 degrees Celsius; 200 degrees Fahrenheit] hotter than in nearby regions and that the difference occasionally reached as much as 400 Kelvin [400 degrees Celsius; 700 degrees Fahrenheit]. Other research had recorded similar effects near the Rocky Mountains in Colorado. After comparing simulations of atmospheric gravity waves and acoustic waves, the researchers found that the acoustic waves reached higher altitudes than the gravity waves, leading them to speculate that the acoustic waves constituted a far more plausible source of the observed hot spots. They then identified wind fluctuations as the most likely source of the heating, noting that the upwind waves could only be generated by unsteady wind flow.

They cite further evidence indicating that the high- frequency acoustic waves in the thermosphere originated from the ground, including proof that nighttime atmospheric motion (convection) is not a plausible source of the persistent heating. In addition, they note that only high-frequency acoustic waves could cause the thermospheric heating, as the slower-speed gravity waves are not fast enough to reach the higher altitudes and therefore could not produce the substantial effects at that height in the atmosphere.

The paper indicates that moderately strong winds, reaching speeds of approximately 10 meters [30 feet] per second, can generate wave amplitudes of nearly four meters [10 feet] per second above rough terrain. In addition, the authors found that steeply sloping terrain further enhanced the waves, which are generated by rapid variations in the up-and-down turbulence in the air. Wider hills and those spaced further apart can also have a similar wave- generating effect, but the authors found that the wind effects typically do not propagate vertically near isolated hills as they do around rougher terrain.

The researchers note that there are very few detailed field studies of the wind field over hills at present. They report, however, that models and previous research indicates that even weak interactions from acoustic waves can produce significant effects in the thermosphere.

Harvey Leifert | EurekAlert!
Further information:
http://www.agu.org

More articles from Earth Sciences:

nachricht Predicting unpredictability: Information theory offers new way to read ice cores
07.12.2016 | Santa Fe Institute

nachricht Sea ice hit record lows in November
07.12.2016 | University of Colorado at Boulder

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

NTU scientists build new ultrasound device using 3-D printing technology

07.12.2016 | Health and Medicine

The balancing act: An enzyme that links endocytosis to membrane recycling

07.12.2016 | Life Sciences

How to turn white fat brown

07.12.2016 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>