Featured Research

from universities, journals, and other organizations

Navy oceanographers delve deeper in wave data to improve forecasts

Date:
October 31, 2012
Source:
U.S. Naval Research Laboratory
Summary:
The U.S. Navy has one of the most active and vital operational oceanography programs in the world. With a greater understanding of wave mechanics, scientists can improve wave forecasts in oceans around the globe.

An example of a raw infrared image of the water surface with observed thermal streaks showing the effect of nonbreaking waves, propagating from right to left, on water in a wave tank. The straight vertical row of bright dotted lines are thermal markers, and the lighter horizontal streaks correspond to elongated, near-surface, eddies.
Credit: U.S. Naval Research Laboratory

Around the globe, mariners and navies alike have long observed and included weather and sea states in navigational planning when plotting course or developing military strategy. And although forecasting had become an integral function by the start of the 20th century, these predictions were often crude and qualitative.

Related Articles


For the U.S. Navy, the years 1941 through 1946 provided an unusual stimulus to ocean wave research, according to pioneer World War II oceanographer Charles Bates. During this brief five-year period, theory, observation, and prediction of sea, swell, and surf made the greatest strides in their history.

As a result, the U.S. Navy has one of the most active and vital operational oceanography programs in the world. Naval oceanography provides critical information to such combat disciplines as anti-submarine warfare, mine warfare and countermeasures, naval special warfare, amphibious operations, and ship transit planning.

Today, U.S. Naval Research Laboratory physicists at the Remote Sensing Division continue to improve the integrity of these forecasts by developing a means to include the effects of the amorphous near-surface phenomenon of turbulence generation by nonbreaking waves.

"Current state-of-the-art ocean wave forecasting numerical models do not take this mechanism into account," says Dr. Ivan Savelyev. "This can potentially account for some forecasting errors and directly impact the Navy's ability to predict wave heights in oceans anywhere in the world."

Historically the parameterization of turbulence production in the upper ocean has primarily relied on the assumptions of wall turbulence, where the wind-generated surface friction velocity acts as a moving boundary. In the top few meters of the ocean another source term is added due to turbulence injection by breaking waves.

Currently there are a number of competing theories and hypotheses attempting to describe a third mechanism, which would account for energy flux from nonbreaking waves to the upper ocean turbulence. However, scarce empirical results struggle to establish the existence of such energy transfer and are not sufficient for thorough validation of existing theories. The variety of approaches is caused, perhaps, both by the complexity of the problem and by the lack of detailed experimental data.

Research being conducted at NRL investigates both experimental and numerical approaches. Turbulent velocities at the water surface were measured in a laboratory wave tank with high precision using the thermal-marking velocimetry technique. Numerically, a fully nonlinear model for the wave motion was coupled with Large Eddy Simulation for the turbulent motion.

Both numerical and laboratory results confirm the turbulence production due to wave motion and the turbulent kinetic energy was found to be a function of time, wave steepness, wave phase, and initial turbulent conditions. Additionally, turbulent motion near the surface was found to be horizontally anisotropic due to the formation of near-surface eddies, elongated in the direction of wave propagation.

"The mechanism responsible for the observed production of turbulence appears to be the result of interaction between pre-existing turbulence and wave motion," says Savelyev. "More specifically, the horizontal shear, associated with wave-induced Stokes drift, stretches and intensifies existing vortices, giving rise to 'streaky' turbulent patterns we observed at the water's surface."

Unlike present wave dissipation formulations, which primarily rely on wave spectrum information, this new mechanism reveals a function of existing turbulence in the upper ocean. This imposes a feedback requirement between ocean circulation and surface wave models and further reveals the added need to couple atmosphere-wave-ocean dynamics within a joint forecasting system.


Story Source:

The above story is based on materials provided by U.S. Naval Research Laboratory. Note: Materials may be edited for content and length.


Cite This Page:

U.S. Naval Research Laboratory. "Navy oceanographers delve deeper in wave data to improve forecasts." ScienceDaily. ScienceDaily, 31 October 2012. <www.sciencedaily.com/releases/2012/10/121031124853.htm>.
U.S. Naval Research Laboratory. (2012, October 31). Navy oceanographers delve deeper in wave data to improve forecasts. ScienceDaily. Retrieved April 17, 2015 from www.sciencedaily.com/releases/2012/10/121031124853.htm
U.S. Naval Research Laboratory. "Navy oceanographers delve deeper in wave data to improve forecasts." ScienceDaily. www.sciencedaily.com/releases/2012/10/121031124853.htm (accessed April 17, 2015).

Share This


More From ScienceDaily



More Earth & Climate News

Friday, April 17, 2015

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Planet Defence Conference Tackles Asteroid Threat

Planet Defence Conference Tackles Asteroid Threat

AFP (Apr. 17, 2015) Scientists gathered at a European Space Agency (ESA) facility outside Rome this week for the Planetary Defence Conference 2015 to discuss how to tackle the potential threat from asteroids hitting Earth. Duration: 00:54 Video provided by AFP
Powered by NewsLook.com
Gulf Scarred, Resilient 5 Years After BP Spill

Gulf Scarred, Resilient 5 Years After BP Spill

AP (Apr. 17, 2015) Five years after the Deepwater Horizon spill in the Gulf of Mexico, splotches of oil still dot the seafloor and wads of tarry petroleum-smelling material hide in pockets in the marshes of Barataria Bay. (April 17) Video provided by AP
Powered by NewsLook.com
Boeing's Autonomous Underwater Vehicles (AUV) Echo Ranger

Boeing's Autonomous Underwater Vehicles (AUV) Echo Ranger

Scuba Diving (Apr. 16, 2015) Seventy years after its service in World War II, NOAA, working with private industry partners, has confirmed the location and condition of the USS Independence. Resting upright in 2,600 feet of water off California’s Farallon Islands, the aircraft carrier’s hull and flight deck are clearly visible in sonar images, with what appears to be a plane in the carrier’s hangar bay. Video provided by Scuba Diving
Powered by NewsLook.com
California Drought Renews Thirst for Desalination Plants

California Drought Renews Thirst for Desalination Plants

Reuters - US Online Video (Apr. 16, 2015) As California&apos;s water crisis deepens, a one billion dollar desalination plant is set to go on-line near San Diego. Nathan Frandino reports. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins