Scientists from the Commerce Department’s National Oceanic and Atmospheric Administration (NOAA) and their colleagues have moved one step closer to understanding hurricane dynamics with a recent breakthrough description of a storm’s vertical wind speed structure and its relation to the tumultuous ocean surface below the storm.
This new characterization, published in the March 20 issue of the science journal Nature, could affect numerous computer models used to predict hurricane motion, intensity, and the associated waves and storm surge that can be devastating to near shore communities.
The discovery is made possible because of new data collected from probes deployed during NOAA’s hurricane field experiments and U.S. Air Force reconnaissance missions. The probes, called Global Positioning System (GPS) dropwindsondes, provide information about the force the wind exerts on the sea surface, information that was previously difficult to measure and thus extrapolated from much weaker storms, a calculation now determined to be an overestimation by the research team.
The team was headed by Mark Powell, a research meteorologist with NOAA’s Atlantic Oceanographic and Meteorological Laboratory in Miami, Fla. and co-authors Peter J. Vickery of the University of Western Ontario, London, Ont.; and Timothy A. Reinhold, Clemson University, Clemson, S.C.
This has been kind of a ‘Holy Grail’ for scientists interested in air-sea interaction in hurricanes as well as engineers interested in the design of ocean structures,” said Powell. “The GPS sondes have provided measurements to help settle this problem in the open ocean. We'll have to launch many more sondes near the coast to see if the results also apply there.”
The finding is significant as it helps determine how the wind acts on the ocean surface to create waves and storm surge, and is also related to the amount of energy supplied from the ocean to the storm in the form of heat, and moisture.
The formulation that describes this energy is employed in applications such as:
There have been impressive strides taken in the quality of tropical cyclone track predictions over the last 10 years, mainly due to improved dynamical models. However, there appears to be little new skill in predicting storm intensity changes,” said Isaac Ginis, a professor at the University of Rhode Island’s Graduate School of Oceanography. “In light of the fundamental role the air-sea interaction processes play in supplying energy to the tropical cyclone, this discovery seems to be one of the most promising for major improvements in tropical cyclone intensity forecasting.”
Ashan Kareem, the Robert M. Moran professor of the University of Notre Dame’s NatHaz Modeling Laboratory, said the findings of Powell and his colleagues reveal the “complexities underlying air-sea interaction with emphasis on the surface drag” and that they “will have a profound influence on the characterization of the wind field over the ocean.”
The Commerce Department's National Oceanic and Atmospheric Administration (NOAA) Office of Oceanic and Atmospheric Research is dedicated to enhancing economic security and national safety through research to better understand weather and climate-related events and to manage wisely our nation's coastal and marine resources.
Learn more about NOAA at: http://www.noaa.gov. For more information about the Atlantic Oceanographic and Meteorological Laboratory, visit: http://www.aoml.noaa.gov.