This paper presents results of a trial of a Pisces HF radar system aimed at assessing its use as a component of a wave-monitoring network being installed around the coasts of England and Wales. The radar system has been operating since December 2003 and the trial continued to June 2005. The data have been processed in near-real time and displayed on a website. Radar measurements of the directional spectrum and derived parameters are compared with those measured with a directional waverider and with products from the Met Office, United Kingdom, operational wave model. Radar measurements of currents and winds are also compared with Met Office model products and, in the case of winds, with the QuikSCAT scatterometer. Statistics on data availability and accuracy are presented. The results demonstrate that useful availability and accuracy in wave and wind parameters are obtained above a waveheight threshold of 2 m and at ranges up to 120 km at the radar operating frequencies (7-10 MHz) used. Waveheight measurements above about 1 m can be made with reasonable accuracy (e.g., mean difference of 2.5% during January-February 2004). Period and direction parameters in low seas are often contaminated by noise in the radar signal. The comparisons provide some evidence of wave model limitations in offshore wind and swell conditions

High Frequency radar (HFR) is a land-based remote sensing instrument offering a unique insight to coastal ocean variability, by providing synoptic, high frequency and high resolution data at the ocean atmosphere interface. HFRs have become invaluable tools in the field of operational oceanography for measuring surface currents, waves and winds, with direct applications in different sectors and an unprecedented potential for the integrated management of the coastal zone. In Europe, the number of HFR networks has been showing a significant growth over the past ten years, with over 50 HFRs currently deployed and a number in the planning stage. There is also a growing literature concerning the use of this technology in research and operational oceanography. A big effort is made in Europe towards a coordinated development of coastal HFR technology and its products within the framework of different European and international initiatives. One recent initiative has been to make an up-to-date inventory of the existing HFR operational systems in Europe, describing the characteristics of the systems, their operational products and applications. This paper offers a comprehensive review on the present status of European HFR network, and discusses the next steps towards the integration of HFR platforms as operational components of the European Ocean Observing System, designed to align and integrate Europe’s ocean observing capacity for a truly integrated end-to-end observing system for the European coasts.

The Chahine-Twomey relaxation method for inversion of the atmospheric radiative transfer equation is extended to provide an inverse solution to Barrick's equation describing second order scatter of high frequency (HF) radio waves from the ocean surface. The success of the method is demonstrated here using synthesised radar Doppler spectra obtained by solving the direct problem with wave buoy directional spectrum measurements. Wave buoy measurements are limited in the range of directional characteristics that can be measured. The results presented here suggest that HF radar is capable of providing a more general measurement of the directional spectrum.

The power spectrum of backscatter from the ocean surface at HF radio frequencies is characterized by two large peaks called the first-order Bragg peaks. These are surrounded by a continuum due to second-order effects. The power spectrum can be described in low to moderate sea states by a nonlinear integral equation relating it to the ocean wave directional spectrum. Inverting this equation provides an estimate of the directional spectrum. A number of inversion methods have been published. In this paper, the Wyatt method is discussed. This method uses the part of the backscatter power spectrum that surrounds the larger Bragg peak. An extension of the method to include the spectrum around the weaker peak is discussed, and some improvements in the solution are demonstrated. Until recently, all published work in this area concerned solutions to a linearized version of the equation. The second extension presented here tackles the nonlinear problem but points out the limitations of the approach and sho... Abstract The power spectrum of backscatter from the ocean surface at HF radio frequencies is characterized by two large peaks called the first-order Bragg peaks. These are surrounded by a continuum due to second-order effects. The power spectrum can be described in low to moderate sea states by a nonlinear integral equation relating it to the ocean wave directional spectrum. Inverting this equation provides an estimate of the directional spectrum. A number of inversion methods have been published. In this paper, the Wyatt method is discussed. This method uses the part of the backscatter power spectrum that surrounds the larger Bragg peak. An extension of the method to include the spectrum around the weaker peak is discussed, and some improvements in the solution are demonstrated. Until recently, all published work in this area concerned solutions to a linearized version of the equation. The second extension presented here tackles the nonlinear problem but points out the limitations of the approach and sho...