Ocean surface wave measurements from a phase array high-frequency radar system in the coastal area of Northwest of Mexico Pacific waters

High frequency radars (HFR) are systems that allow us to monitor some oceanographic variables through the backscatter signal from the ocean surface.  Typically, they provide us with a relatively high space-time resolution of surface currents and the wave field, very important local information to be used for maritime operation applications, such as search and rescue, safety at sea and transportation, and marine energy resources assessment.  Although the main product from HFR is ocean surface currents, they can in addition, provide useful information to derive important characteristics of the wave field, such as significant wave height (Hs) and even the directional spectrum. We, nevertheless, focus our attention in this work in the wave field, and specifically Hs values. A HFR (WERA system) is in operation in Todos Santos Bay, Ensenada, Mexico, since March 2021. Maps of significant wave height are estimated every hour over an area of approximately 250 km2 with spatial resolution of 800 m. These measurements have been compared with wave data derived from three moored instruments (ADCP), the results yielded correlations greater than 0.7 and RMSE values less than 40 cm. In the last two decades this technology has been implemented throughout the world, although there is very limited detail on calibration and validation of the instrument with local ocean wave conditions, especially with respect to the presence of swell. In this study, an empirical calibration is performed using an algorithm provided by the manufacturer in which a correction parameter  is obtained according to the operating frequency of the radar, in particular a WERA system. This study takes into consideration some particular characteristics of the area of interest and the performance of the correction parameter is determined as a function of the wave height and direction of travel relative to the radial direction from the WERA site.