Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Ocean spray lubricates hurricane winds

26.07.2005


Hurricane Emily’s 140-mile-per-hour winds, which last week blew roofs off hotels and flattened trees throughout the Caribbean, owed their force to an unlikely culprit – ocean spray.



According to a new study by two University of California, Berkeley, mathematicians and their Russian colleague, the water droplets kicked up by rough seas serve to lubricate the swirling winds of hurricanes and cyclones, letting them build to speeds approaching 200 miles per hour. Without the lubricating effect of the spray, the mathematicians estimate, winds would rise to little more than 25 miles per hour.

"This is not a small effect," said Alexandre Chorin, professor of mathematics at UC Berkeley and faculty researcher at Lawrence Berkeley National Laboratory (LBNL). He and fellow UC Berkeley mathematics professor Grigory I. Barenblatt, also of LBNL, along with V. M. Prostokishin of the Shirshov Institute of Oceanology in Moscow, published their analysis of the effect of ocean spray in the Early Online Edition of the Proceedings of the National Academy of Sciences.


Over the past decade, the three mathematicians have developed a body of equations to describe turbulence in fluids and have applied these equations to many practical problems. Turbulence slows flowing liquids or gases by generating eddies, swirls and vortices, and thus plays a role in keeping airplanes aloft, slowing ships and taming rivers.

"Turbulence is generally a good thing," Chorin said, noting that without turbulence the Mississippi River at its mouth would be flowing at supersonic speed. "You need turbulence to make friction stronger."

The equations, when applied to a cloud of water droplets sandwiched between flowing air and water, indicate that large water droplets thrown up by cresting waves in rough seas inhibit the turbulence in the air over the ocean. Without this turbulence to drain energy from the swirling winds, winds can build to tremendous speeds. Without turbulence, friction between the air and water would be reduced by a factor of 1,000, Chorin said, sometimes allowing winds to rise to speeds eight times greater than would be the case with turbulence.

The turbulent vortices in the air are suppressed by the droplets when they rain back into the sea, somewhat like "combing unruly hair," Chorin said. These droplets are about 20 microns across (8 ten-thousandths of an inch) or larger.

The smaller the droplets, the less ability they have to suppress the turbulence, he said, which suggests one way to calm hurricanes.

"If you could develop a detergent to reduce the size of the droplets, you might be able to stop a hurricane," he said. "That’s not as far fetched as it sounds. In ancient times, sailors carried oil to pour out on the water to calm storms. Pouring oil on choppy waters was not a superstition."

In their paper, the mathematicians conclude that "We think that the action of oil was exactly the prevention of the formation of droplets! The turbulence was restored after the oil was dropped, the turbulent drag increased, and the intensity of the squall was reduced. Possibly hurricanes can be similarly prevented or damped by having airplanes deliver fast decaying harmless surfactants to the right places on the sea surface."

The team began working on the problem after a colleague, Sir M. James Lighthill, suggested to Barenblatt at a party that drops in ocean spray might have a lubricating effect on hurricane winds. Hurricanes or, more properly, tropical cyclones, form at low-pressure areas over warm, tropical oceans. Swirling air is accelerated by energy from the warm water.

Lighthill was unable to solve the problem before his untimely swimming death in 1998, but his friends took on the task employing their turbulence models. The paper is dedicated to "the great mathematician and fluid mechanician Sir James Lighthill."

Whereas Lighthill thought that evaporation of the droplets cooled the atmosphere and led to accelerated winds, Chorin, Barenblatt and Prostokishin have showed that more important is the reduction of turbulence by falling droplets. Nevertheless, they note that evaporative cooling also serves to reduce turbulence and thus allow winds to build.

Robert Sanders | EurekAlert!
Further information:
http://www.berkeley.edu

More articles from Earth Sciences:

nachricht Climate change weakens Walker circulation
20.10.2017 | MARUM - Zentrum für Marine Umweltwissenschaften an der Universität Bremen

nachricht Shallow soils promote savannas in South America
20.10.2017 | Senckenberg Forschungsinstitut und Naturmuseen

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Terahertz spectroscopy goes nano

20.10.2017 | Information Technology

Strange but true: Turning a material upside down can sometimes make it softer

20.10.2017 | Materials Sciences

NRL clarifies valley polarization for electronic and optoelectronic technologies

20.10.2017 | Interdisciplinary Research

VideoLinks
B2B-VideoLinks
More VideoLinks >>>