Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Carbon dioxide and the ocean

12.03.2007
Hurricane can form new eyewall and change intensity rapidly

Hurricanes can gain or lose intensity with startling quickness, a phenomenon never more obvious than during the historic 2005 hurricane season that spawned the remarkably destructive Katrina and Rita.

Researchers flew through Rita, Katrina and other 2005 storms trying to unlock the key to intensity changes. Now, data from Rita is providing the first documented evidence that such intensity changes can be caused by clouds outside the wall of a hurricane's eye coming together to form a new eyewall.

“The comparison between Katrina and Rita will be interesting because we got excellent data from both storms. Rita was the one that showed the eyewall replacement,” said Robert Houze Jr., a University of Washington atmospheric sciences professor and lead author of a paper detailing the work in the March 2 edition of the journal Science.

“The implication of our findings is that some new approaches to hurricane forecasting might be possible,” he said.

Houze and Shuyi Chen, an associate professor of meteorology and physical oceanography at the University of Miami Rosenstiel School of Marine and Atmospheric Science, lead a scientific collaboration called the Hurricane Rainband and Intensity Change Experiment. The project is designed to reveal how the outer rainbands interact with a hurricane's eye to influence the storm's intensity. Chen is a co-author of the Science paper, as are Bradley Smull of the UW and Wen-Chau Lee and Michael Bell of the National Center for Atmospheric Research in Boulder, Colo.

The project is the first to use three Doppler radar-equipped aircraft flying simultaneously in and near hurricane rainbands. The project also uses a unique computer model developed by Chen's group at the Rosenstiel School.

“The model provided an exceptionally accurate forecast of eyewall replacement, which was key to guiding the aircraft to collect the radar data,” Chen said.

A hurricane's strongest winds occur in the wall of clouds surrounding the calm eye. The researchers found that as the storm swirled into a tighter spin, a band of dry air developed around the eyewall, like a moat around a castle. But while a moat protects a castle, the hurricane's moat eventually will destroy the existing eyewall, Houze said. Meanwhile, outer rainbands form a new eyewall and the moat merges with the original eye and the storm widens, so the spin is reduced and winds around the eye are slowed temporarily, something like what happens as a figure skater's arms are extended. But the storm soon intensifies again as the new eyewall takes shape.

“The exciting thing about the data from Rita is that they show that the moat is a very dynamic region that cuts off the old eye and establishes a wider eye,” Houze said. “It's not just a passive region that's caught in between two eyewalls.”

Hurricane forecasters in recent years have developed remarkable accuracy in figuring out hours, even days, ahead of time what path a storm is most likely to follow. But they have been unable to say with much certainty how strong the storm will be when it hits land. This work could provide the tools they need to understand when a storm is going to change intensity and how strong it will become.

Scientists already knew that intensity can change greatly in a short time – in the case of Rita the storm grew from a category 1, the least powerful hurricane, to a category 5, the most powerful, in less than a day. Aircraft observation of the moat allowed scientists to see Rita's rapid loss of intensity during eyewall replacement, which was followed by rapid intensification.

“Future aircraft observations focused in the same way should make it possible to identify other small-scale areas in a storm where the processes that affect intensity are going on, then that data can be fed into high-resolution models to forecast storm intensity changes,” Houze said.

That understanding could prove valuable for coastal residents deciding whether a storm is powerful enough to warrant their seeking safety farther inland. Rita and Katrina, among the six most intense Atlantic hurricanes ever recorded in terms of the barometric pressure within the core of the storm, struck just three weeks apart in August and September 2005, together resulting in some 2,000 fatalities and more than $90 billion in damage along the Gulf of Mexico coastline. The most-intense Atlantic storm ever recorded, Wilma, also struck in the record-setting 2005 hurricane season, which produced 15 hurricanes, including a fourth category 5 storm, Emily, and a category 4 storm, Dennis.

The National Oceanic and Atmospheric Administration provided two research aircraft for the project and the third was provided by the U.S. Navy and funded by the National Science Foundation.

The planes flew several novel flight paths, including a circular track in Rita's moat, to gather information from the edges of rainbands and other structures in the hurricane.

“We used a ground-control system with a lot of data at our fingertips to focus the aircraft into places in the storm where there were processes happening related to intensity changes,” Houze said.

Rosenstiel School is part of the University of Miami and, since its founding in the 1940s, has grown into one of the world's premier marine and atmospheric research institutions.

Ivy Kupec | EurekAlert!
Further information:
http://www.rsmas.miami.edu

More articles from Earth Sciences:

nachricht NASA examines Peru's deadly rainfall
24.03.2017 | NASA/Goddard Space Flight Center

nachricht Steep rise of the Bernese Alps
24.03.2017 | Universität Bern

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Argon is not the 'dope' for metallic hydrogen

24.03.2017 | Materials Sciences

Astronomers find unexpected, dust-obscured star formation in distant galaxy

24.03.2017 | Physics and Astronomy

Gravitational wave kicks monster black hole out of galactic core

24.03.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>