Lessons Learned

cable spools

The two radar groups using BF techniques (WERA) were, in general, pleased with the wealth of data provided by this system, including the possibility of near real-time directional wave capabilities. These measurements are not only important to the modeling programs, but are needed to interpret radar-derived surface velocity fields and directional waves in strongly sheared ocean regimes (i.e. Florida Current). In collaboration with our European colleagues, more significant inroads must be made in this area of radar-derived directional waves, as it is an exciting area of scientific and research inquiry that has operational potential. This remote sensing capability is a plus in regimes such as the Gulf Stream and Florida Current where surface buoys are difficult to deploy and maintain over long periods. Notwithstanding, there were drawbacks with BF system:

  • Cabling necessary to support the independent Rx antennae makes the system difficult to relocate quickly. However, the nearly constant criticism on the number of Rx antennae along the beach, deemed a drawback by the radar community, has not been an issue for our installations.

  • Processing and post-processing software is in need of improved documentation, but it is open source to the user groups, which we consider a significant advantage.

  • Support of the system is forthcoming from the vendor, but is logistically difficult to acquire, given the time zone offset between the U.S. East Coast and Germany, and some communication difficulties. This issue has been minimized since the vendor now has a North American partner in Canada although that firm will need training in the deployment, operations and maintenance aspects of the radar.

  • There is a need to determine the optimal time integration to acquire good directional wave estimates where the installations must have at least 12-element Rx arrays.

The two radar groups using DF techniques (SS) experienced a number of difficulties as well:

  • The 5 MHz band is noisy and at times is used in Homeland Security operations (UNC had to stop transmitting at two of its permitted frequencies at the request of the FCC).

  • Reliable measurements of surface currents off the Outer Banks remains elusive due to the combined effect of increased noise levels and broad Bragg peaks; the result can be a sizable decrease in useful data owing to vectors that were not oriented correctly.

  • Significant wave height is valid over the domain and not individual cells or bins as in BF mode. Since only one antennae system is used, the DF algorithms do not provide the directional wave capability.

  • Parameters in the MUSIC algorithm need more exploration to establish both the strengths and weaknesses of the system for the NOAA IOOS-sponsored U. S. National Network.

Regardless of the radar systems, accuracy and error statistics (i.e. uncertainties) are important for this purpose for not only radial velocities, but just as importantly for the vector surface currents as well.