Coastal high-frequency radars in the Mediterranean - Part 2: Applications in support of science priorities and societal needs

The Mediterranean Sea is a prominent climate-change hot spot, with many socioeconomically vital coastal areas being the most vulnerable targets for maritime safety, diverse met-ocean hazards and marine pollution. Providing an unprecedented spatial and temporal resolution at wide coastal areas, high-frequency radars (HFRs) have been steadily gaining recognition as an effective land-based remote sensing technology for continuous monitoring of the surface circulation, increasingly waves and occasionally winds. HFR measurements have boosted the thorough scientific knowledge of coastal processes, also fostering a broad range of applications, which has promoted their integration in coastal ocean observing systems worldwide, with more than half of the European sites located in the Mediterranean coastal areas. In this work, we present a review of existing HFR data multidisciplinary science-based applications in the Mediterranean Sea, primarily focused on meeting end-user and science-driven requirements, addressing regional challenges in three main topics: (i) maritime safety, (ii) extreme hazards and (iii) environmental transport process. Additionally, the HFR observing and monitoring regional capabilities in the Mediterranean coastal areas required to underpin the underlying science and the further development of applications are also analyzed. The outcome of this assessment has allowed us to provide a set of recommendations for future improvement prospects to maximize the contribution to extending science-based HFR products into societally relevant downstream services to support blue growth in the Mediterranean coastal areas, helping to meet the UN's Decade of Ocean Science for Sustainable Development and the EU's Green Deal goals

Coastal high-frequency radars in the Mediterranean - Part 1: Status of operations and a framework for future development

Due to the semi-enclosed nature of the Mediterranean Sea, natural disasters and anthropogenic activities impose stronger pressures on its coastal ecosystems than in any other sea of the world. With the aim of responding adequately to science priorities and societal challenges, littoral waters must be effectively monitored with high-frequency radar (HFR) systems. This land-based remote sensing technology can provide, in near-real time, fine-resolution maps of the surface circulation over broad coastal areas, along with reliable directional wave and wind information. The main goal of this work is to showcase the current status of the Mediterranean HFR network and the future roadmap for orchestrated actions. Ongoing collaborative efforts and recent progress of this regional alliance are not only described but also connected with other European initiatives and global frameworks, highlighting the advantages of this cost-effective instrument for the multi-parameter monitoring of the sea state. Coordinated endeavors between HFR operators from different multi-disciplinary institutions are mandatory to reach a mature stage at both national and regional levels, striving to do the following: (i) harmonize deployment and maintenance practices; (ii) standardize data, metadata, and quality control procedures; (iii) centralize data management, visualization, and access platforms; and (iv) develop practical applications of societal benefit that can be used for strategic planning and informed decision-making in the Mediterranean marine environment. Such fit-for-purpose applications can serve for search and rescue operations, safe vessel navigation, tracking of marine pollutants, the monitoring of extreme events, the investigation of transport processes, and the connectivity between offshore waters and coastal ecosystems. Finally, future prospects within the Mediterranean framework are discussed along with a wealth of socioeconomic, technical, and scientific challenges to be faced during the implementation of this integrated HFR regional network

4D-Var data assimilation and observation impact on surface transport of HF-Radar derived surface currents in the North-Western Mediterranean Sea

We investigated the effect of the assimilation of surface velocities from two HF-Radars (HFRs) and satellite sea surface temperature (SST) into an ocean circulation model, implemented on the North-Western Mediterranean Sea, using the ROMS 4D-Var Data Assimilation (DA) System. A three months period from September to November 2020 is analysed. A model free run is used as reference simulation to quantify the impact of the data assimilation procedure on the surface circulation. The DA framework consists of a sequence of 3-day windows during which the observations are assimilated into the model, followed by forecast simulations, starting from the last time step of the analysis run. The comparison of simulated velocities and SST against the assimilated observations shows that both forecast and analysis runs improve the solution as compared to the freerun, with error reduction up to the 47% and doubling of correlation values. If SST is not assimilated, the simulated sea surface temperature slightly degrades as a result of the DA procedure. Furthermore, we used surface velocities from Lagrangian drifters to test the model against independent observations. The results show that both the forecast and the analysis simulate surface circulation better than the free run within the areas covered by HFR observations, with error reduction ranging from 10% to 50%, and increase in correlation from 5% to more than doubled. Nevertheless, farther afield, outside the area covered by HFRs, improvements and degradations of the solution due to the DA procedure balance each other. The impact of assimilated observation on the alongshore transport of the upper 50 m is analysed along three transects adjacent to the two HFR areas and along a section in between. The transport increment is significant where the surface velocities are assimilated whereas it is negligible elsewhere. The effect of SST is to modify the velocity distribution along the transects, while keeping the transport increment unchanged. Modifications to the initial conditions have the most significant effect on the alongshore transport, whereas the corrections to boundary conditions and atmospheric forcing have different importance according to the analysed transects. The assimilation of surface velocities and SST affects more the ageostrophic component of the surface velocity field, rather than the geostrophic one

Strumenti e indicazioni di governance transfrontaliera. Piano d’azione e linee guida del progetto IMPACT [Instruments et indications pour la gouvernance transfrontalière. Plan d’action et lignes directrices du projet IMPACT]

Il presente documento restituisce una sintesi delle attività del progetto IMPACT ed è diviso in due parti. La prima parte evidenzia gli strumenti completati durante la durata del progetto, in particolare la rete di radar costieri per il monitoraggio delle correnti marine e la piattaforma webGIS per la consultazione dei dati raccolti ed elaborati dai partner di progetto. La seconda parte capitalizza sui suddetti strumenti per fornire sia indicazioni metodologiche che di governance. Nello specifico, la rete di radar costieri viene utilizzata per creare mappe di potenziale contaminazione e indicare in che condizioni le attività portuali possano essere più sostenibili. Le misure demografiche e i calcoli di ritenzione indicano il livello d’efficacia delle dimensioni attuali delle AMP mentre le misure di contaminazione suggeriscono di considerare un numero maggiore di stazioni nell’ottica di migliorare i piani di monitoraggio esistenti. In quest’ottica, le indicazioni rappresentano il piano d’azione e le linee guida del progetto. L’ulteriore espansione della rete di radar costieri prevista nei progetti SICOMAR plus e SINAPSI è la prova che la conclusione delle attività del progetto IMPACT sia in realtà solo un importante punto di partenzaCe document donne un résumé des activités du projet IMPACT et est divisé en deux parties. La première partie met en évidence les instruments réalisés pendant la durée du projet, en particulier le réseau de radars côtiers pour la surveillance des courants marins et la plate-forme webGIS pour la consultation des données collectées et traitées par les partenaires du projet. La deuxième partie s’appuie sur ces outils pour fournir des orientations à la fois méthodologiques et de gouvernance. Plus précisément, le réseau de radars côtiers est utilisé pour créer des cartes de contamination potentielle et indiquer dans quelles conditions les activités portuaires peuvent être plus durables. Les mesures démographiques et les calculs de rétention indiquent le niveau d’efficacité de la taille actuelle des AMP, tandis que les mesures de contamination suggèrent que davantage de stations devraient être envisagées en vue d’améliorer les plans de surveillance existants. Dans cette perspective, les indications représentent le plan d’action et les lignes directrices du projet. La poursuite de l’extension du réseau de radars côtiers prévue dans les projets SICOMAR plus et SINAPSI est la preuve que la conclusion des activités du projet IMPACT n’est en fait qu’un point de départ important