Surface ocean radial velocities obtained by HF-radar from stations located along coastal waters of Hawaii, North Slope Alaska, Gulf of Alaska, Puerto Rico/Virgin Islands, eastern U.S./Gulf of America, western U.S., and the Great Lakes

This dataset contains surface ocean radial velocities data obtained by HF-radar from stations located along coastal waters of the United States. Radial velocity files contain metadata in a key-value format, while the measured velocities and associated ancillary data are reported in a tab-delimited format.

The National Data Buoy Center (NDBC) — in collaboration with the Scripps Institution of Oceanography through June 2025 and thereafter with NOAA’s National Environmental Satellite, Data, and Information Service (NESDIS) — assembles the data from the Integrated Ocean Observing System (IOOS) Surface Currents Program’s High-Frequency (HF) Radar National Network and submits the data on a monthly basis to NOAA’s National Centers for Environmental Information (NCEI).

Remote sensing of ocean surface velocity from shore-based HF-radar sensors bridges an operational observational gap between point samples obtained from in-situ sampling and synoptic scale relatively low resolution data obtained from satellites by providing continuous mesoscale coverage at relatively high resolution near the coast. HF-radar systems measure the speed of ocean surface currents in directions radial to the antenna in near real time. Radial velocities alone are a measurement of surface ocean velocity projected along the direction radial to the antenna, which only show those currents’ movement towards or away from the HF-radar sensor’s antenna. Radial measurements of ocean velocity may be used directly in some applications such as model assimilation but are commonly used in combination with overlapping sites to estimate the total vector ocean velocity.

Systems operate continuously in all weather conditions and are installed near the coastline. Range resolution of measured currents is determined by the radar transmit bandwidth used. Bandwidth is controlled by radio frequency licenses and translates to range resolutions of 0.5 to 6 kilometers. Maximum ranges of current measurements also depend on radar transmit frequency and vary from about 40 km offshore to about 200 km offshore. Velocities are measured in the upper 0.3 - 2.5 meters of the ocean depending on the operating frequency and vertical velocity shear profile.