Lagrangian Float Deployments into the Ocean Beneath Hurricane Dennis

Eric D'Asaro (homepage), Applied Physics Laboratory, University of Washington

Hurricanes draw their energy from warm ocean waters, but cool the warm ocean beneath them by mixing up cold water from below. Forecasters can accurately predict the track that hurricanes will take, but not their intensity. This is partially because they do not properly model the cooling of the upper ocean during hurricane passage.(A recent paper on this subject) In August, 1999 we air-deployed three Lagrangian floats into Hurricane Dennis in order to study mixing in the ocean beneath a hurricane.

The image below shows Dennis off the Carolinas, having just brushed past Florida. The colors show the underlying ocean temperature. (Get the this and other images at full resolution here) The orange band is the Gulf Stream flowing northward off Florida. Sea surface temperatures before Dennis were mostly above 30 C. The image shows temperatures 3 days after Dennis' passage. They range from about 30C in the Gulf Stream to 26.5C in blue band to east. Dennis has cooled the upper ocean dramatically.

The purpose of our float deployments was to study this cooling. We deployed floats ahead of Dennis at the locations marked above and let the storm run over them.

Learn more at these links

Mission overview figure - What we did and what we learned.

Image of Dennis over the floats with superimposed winds and storm track - The floats passed near and possibly through the eye, but certainly through the strong winds on the edge of the eye.

Pictures of a test airdrop - Cool pics of how a parachute deploys.

The airdrop package - (in case you want to build one)

Data telemetry

Data from a float with interpretation

A short paper on scientific results(Pdf 323kB) - For 24th conference on Hurricanes,June 2000

A full-length JPO paper (Pdf 1MB) -

More about these floats - The Labrador Sea Deep Convection Experiment (also see Home)

Other Hurricane Links

National Hurricane Center --- (list of more links)

Hurricane/Ocean interaction studies at U.Miami

AirExpendableProbes from Sippican Used to measure hurricane-induced currents

This work was supported by the National Science Foundation, Ocean Sciences Division- THANKS!