Sea of Galilee yields clues for weather forecasting

September 19, 2001

GALVESTON, September 19 - Oceanographer Ayal Anis has studied the lake where Christ walked on the water, but rather than focusing on religious questions, his research aims to shed light on the process by which surface waves transfer energy from the air to the water.

Anis, a professor of marine science at Texas A&M University at Galveston, analyzed the physical response of the Sea of Galilee to external forcing. His study, initially funded by the U.S.-Israel Binational Science Foundation, indicated that the most intense mixing occurred closest to the lake's shores, not in its center and produced results that should be applicable to other bodies of water as well.

Continuing his research at TAMUG under a grant from the Office of Naval Research, Anis is seeking to extrapolate findings from his lake research to the oceans. His current research aims to shed light on the processes by which energy and momentum are transferred from the atmosphere to the ocean, with a specific emphasis on the role of surface waves in these processes.

"Waves at the surface of bodies of water, where air and water interface, are an important agent in the mixing of heat energy from air molecules into the water immediately below them," Anis said. "Momentum from the air molecules also transfers to the water molecules through the surface waves. An understanding of these processes proves crucial for constructing computer models that will be able to accurately predict currents and temperatures in the ocean, similar to what meteorologists are doing when forecasting the weather."

Working with Robert Miller, a professor at Oregon State University, Anis observed intense internal wave activity near the lake's shores (internal waves are similar to those observed on the water surface, but usually have much larger vertical amplitudes). Near the lake's center, which is farther away from the boundaries, much less activity was observed, with relatively little mixing and little internal wave motion.

A suite of numerical models, with an increasing level of complexity, was developed to predict thermal and velocity structure under various forcing scenarios. The performance of these models was then compared to an extensive data set collected in the lake during the study.

"If the air-water energy and momentum exchange at the boundary between the air and the ocean surface is not modeled correctly, ocean forecasts will be erroneous," Anis said. "Unfortunately, earlier models have mostly disregarded the impact of surface wave action on energy exchange, but we can't simply assume that the action of winds on the ocean has the same result as wind blowing over land.

"For example, weak surface waves may limit mixing to the upper meters of the ocean, while large surface waves and intense wave breaking may cause intense turbulence that can enhance mixing to greater depths," he observed. "Therefore, it is extremely important to get the energy mixing component of the model right. If our understanding of this part is wrong, the models we construct will produce unreliable predictions."

"In addition to providing accurate driving forces for models, understanding ocean mixing processes is also important to the study of other oceanic issues such as fishes. For example, turbulence and mixing processes may have a pronounced effect on the development of juvenile fish through predator-prey interactions: when turbulence is intense we may expect a higher success rate for the predator to encounter prey."
-end-
Contact: Judith M. White, 979-845-4664, jw@univrel.tamu.edu; Ayal Anis, 409-740-4987, anisa@tamug.tamu.edu.

Texas A&M University

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