Hurricanes make themselves heard – even under water. So why not use that sound to safely gauge how destructive a storm will be before it makes landfall?
Joshua Wilson and Nicolas Makris at the Massachusetts Institute of Technology reckoned that the frequency of the underwater din of a hurricane whipping up waves might correspond to its intensity.
They took recordings made by an underwater listening device called a hydrophone placed on the floor of the mid-Atlantic during hurricane Gert in 1999, and compared these readings with concurrent satellite data and wind speed measurements made by US military aircraft.
As Gert passed over the hydrophone, the frequency of the noise peaked twice, corresponding to the strong winds on either side of the storm’s eye as it passed over.
The team found that the frequency of the underwater sound correlated to the cube of the wind speed recorded by the aircraft (Geophysical Research Letters, DOI: 10.1029/2008GL033200).
Planting hydrophones in hurricane-prone regions would be cheaper and safer than using aircraft to gauge their intensity, but just as accurate, the researchers claim.
They could be really useful in regions such as the Pacific and Indian Oceans, where specialised aircraft are often not available.