Wave's-eye view of a hurricane.Strong hurricanes aren't as effective as weak ones at transmitting wind energy to the ocean's surface, a counterintuitive coun·ter·in·tu·i·tive adj. Contrary to what intuition or common sense would indicate: "Scientists made clear what may at first seem counterintuitive, that the capacity to be pleasant toward a fellow creature is ... finding that may enable researchers to better estimate the size of storm surges. When winds blow across the ocean, aerodynamic drag--friction where air and water meet--transfers some of the wind's momentum to the water. That transfer creates waves and currents. Scientists have long presumed that higher wind speeds result in higher drag and larger momentum transfers, says William J. Teague, an oceanographer at the Naval Research Lab oratory oratory, the art of swaying an audience by eloquent speech. In ancient Greece and Rome oratory was included under the term rhetoric, which meant the art of composing as well as delivering a speech. in Bay St. Louis, Miss. However, he and his colleagues now report field data that contradict that notion. Six current-measuring instruments were fortuitously sitting on the seafloor in the path of Hurricane Ivan This article is about the Atlantic hurricane of 2004. For other storms of the same name, see Tropical Storm Ivan (disambiguation). Hurricane Ivan was the strongest hurricane of the 2004 Atlantic hurricane season. , which struck the Gulf Coast in mid-September 2004 (SN: 6/11/05, p. 382). From the speed and direction of subsurface currents Subsurface currents are oceanic currents that flow beneath and usually independently of surface currents. Most are very deep, and as such, very little is known about these currents. Subsurface currents are obviously currents below the surface. , Teague and his colleagues estimated the hurricane's wind speed and a parameter called the coefficient of drag Noun 1. coefficient of drag - the ratio of the drag on a body moving through air to the product of the velocity and the surface area of the body drag coefficient coefficient - a constant number that serves as a measure of some property or characteristic , which describes how efficiently the wind's momentum transfers to surface waters. The coefficient of drag reached its peak when wind speeds measured around 115 kilometers per hour--a pace just shy of the threshold for a category 1 hurricane, the team reports in the March 23 Science. Beyond that peak, the drag coefficient Noun 1. drag coefficient - the ratio of the drag on a body moving through air to the product of the velocity and the surface area of the body coefficient of drag coefficient - a constant number that serves as a measure of some property or characteristic steadily dropped as wind speeds increased. That might have been because hurricane-force winds caused large waves to break, dissipating energy through the prodigious generation of ocean spray, bubbles, and foam, Teague says. |
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