In the framework of the SNO/SOERE MOOSE (Mediterranean Ocean Observing System on Environment) program, the Mediterranean Institute of Oceanography is operating coastal High Frequency Surface Wave Radars (HF radar) on the North Western Mediterranean coast. HF radar provide high resolution (3­-5 km), synoptic view of surface currents from the shore up to 80 km off shore at hourly time scales. The measurement principle is based on the Doppler effect created by an additional current on the intrinsic speed of the waves selected by radar-sea interactions, called Bragg waves, having a wavelength of half that of the radar e.m. waves and propagating in the axis of observation (radial currents). A single radar scans the sea in azimuth and determines the radial components of the current at each adjacent cell along each azimuth. Two separate radars for the same area from different angles then collect the information necessary for mapping vector current from the combination of the two sets of radial components.

The MOOSE HF radar MEDTLN data set is made of daily averaged surface currents, geo-referenced on Cartesian lon/lat coordinates. Those are computed from hourly total velocity data of level L3B (velocity threshold and GDOP threshold tests passed) for which additional RFI outliers’ eliminations are made using a one inertial period (17h at 43°N) statistical method based on the number of L3B valid data, variance and mean over the 17h period by reference to the long term (full dataset) statistics. The associated quality control (QC) indexes for the hourly data range from 0 (missing or bad values) to 4 (best confidence values). Details of the method available on the MOOSE HFradar website. Velocities, variances and QC values in this file are those averaged on a lunar daily basis (25 hours average) centered at noon of each day. Hourly data for specific studies may be available on equest (see contacts below).