Surface Current Radar
Briefly, the concept of Doppler radar is used to measure the
two-dimensional surface velocity fields. The approach is similar to
that of a policemen measuring the speed of a car. In our case, an array
of receive antennae are placed along the beach along with a transmit
antennae. The transmitter sends out radio waves at a particular
frequency, that bounces off ocean surface waves of one-half the radar
wavelength (known as Bragg wave). The backscattered signals from the
Bragg waves are received by the array of antennae from which a radial
current is determined from a Doppler spectrum. To measure the
2-dimensional surface flows, two stations are required usually over a
baseline distance of approximately 25-50 km depending on the
transmitter frequency. The radial current from each is combined based
on the geometric configuration of the grid and the intersection angles
between the two stations.
Over the past decade, the University of Miami used the Ocean Surface Current Radar (OSCR) under several venues from the Florida Keys to the New York Harbor. Recently, a "Wellen Radar" (WERA) system has been installed with stations on Key Largo, Key Biscayne, and at Dania Beach. The WERA, designed by University of Hamburg scientists, offers a longer range of 80 to 100 km, sufficient to cover the width of the Strait of Florida across to the Bahamas. The WERA also offers a variable time and space resolution depending on the approved bandwidth by the Federal Communications Commission. The current SE Florida WERA system has been operating since late 2004. Surface current maps are available on the web in near-real time. ---> Click here for the current Florida Strait currents. <---
Over the next few years, we envision a network of WERA deployments from Key West to as far north as Jacksonville to map large-scale surface velocity field in support of the Coastal Ocean Observing Systems. In addition to surface currents, the technology allows one to map significant wave height, wind direction and the 2-dimensional direction wave spectra in real time. Such grided data will also be useful to assimilate into ocean models. This research is currently supported by ONR through the SEA-COOS grant at the University of North Carolina.
For further information and for specific experiments see Dr. Lynn "Nick" Shay's personal web page.