Evaluating High-Frequency radar data assimilation impact in coastal ocean operational modelling

Abstract

Abstract. The impact of the assimilation of HFR (High-Frequency Radar) observations in a high-resolution regional model is evaluated, focusing on the improvement of the mesoscale dynamics. The study area is the Ibiza Channel, located in the Western Mediterranean Sea. The resulting fields are tested against trajectories from 13 drifters. Six different assimilation experiments are compared to a control run (no assimilation). The experiments consists in assimilating (i) Sea surface temperature, sea level anomaly and Argo profiles (generic observation dataset); the generic observation dataset plus (ii) HFR total velocities and (iii) HFR radial velocities. Moreover, for each dataset two different initialization methods are assessed: a) restarting directly from the analysis after the assimilation or b) using an intermediate initialization step applying a strong nudging towards the analysis fields. The experiments assimilating generic observations plus HFR total velocities with the direct restart provides the best results, improving by 53 % the average separation distance between drifters and virtual particles after the first 48 hours of simulation in comparison to the control run. When using the nudging initialization step, the best results are found when assimilating HFR radial velocities, with a reduction of the mean separation distance by around 48 %. Results show the capability of the Ensemble Optimal Interpolation data-assimilative system to correct surface currents not only inside but also beyond the HFR coverage area. The assimilation of radial observations benefits from the smoothing effect associated with the application of the intermediate nudging step.

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

“…As shown in Sect. 2.1.2 of the present work, HFR surface current data assimilation has been demonstrated to improve the model performance in many studies (Paduan and Shulman, 2004;Barth et al, 2008;Hernández-Lasheras et al, 2021). Furthermore, HFR standard data distribution in near-real time throughout the main European marine data portals, facilitating data access and ensuring timeliness, makes them ideal for efficient data assimilation in operational modeling (Capet et al, 2020).…”

“…Moreover, coastal ocean surface current and wave realtime information, which represents the primary and secondary basic products of HFRs, respectively, is being used extensively by search and rescue (Ullman et al, 2006;Ličer et al, 2020;Révelard et al, 2021), environmental agencies for pollutant monitoring of oil spills (Abascal et al, 2009), marine litter tracking (Declerck et al, 2019), recreational activities, navigational safety, ports and shipping, ship detection and tracking (Ponsford et al, 2001;Dzvonkovskaya et al, 2007;Maresca et al, 2013;Laws et al, 2016), coastal and offshore engineering applications, aquaculture, marine renewables (Wyatt, 2012;Basáñez and Pérez-Muñunzuri, 2021;Mundaca-Moraga et al, 2021), and early warning detection systems for natural hazards (Lipa et al, 2006;Gurgel et al, 2011;Grilli et al, 2015;Guérin et al, 2018), among others. Furthermore, the mapping of surface currents at high spatiotemporal resolution provided by the HFRs in the coastal strip allow us to use them as a ground truth for coastal model real-time assessment (Wilkin and Hunter, 2013;Lorente et al, 2016Lorente et al, , 2019bMourre et al, 2018;Aguiar et al, 2020) and improvement through HFR data assimilation (Breivik and Saetra, 2001;Paduan and Shulman, 2004;Barth et al, 2008;Iermano et al, 2016;Hernández-Lasheras et al, 2021), as well as for the evaluation of coastal remote sensing products (Manso-Narvarte et al, 2018;Gommenginger et al, 2021). The development of advanced HFR data products such as gap-filled nowcasts and Lagrangian trajectories allows us to satisfactorily estimate transport, making HFR data a key asset in the assessment and protection of the coastal marine environment, including dispersal and retention of particles (Cianelli et al, 2017;…”

Coastal HF radars in the Mediterranean: Applications in support of science priorities and societal needs

“…More recently, Hernández-Lasheras et al (2021) specifically assessed the impact of assimilating HFR observations on the surface currents in the Ibiza Channel using the WMOP operational system. They compared the performance of both radial and total daily mean HFR-Ibiza surface currents for correcting meso and submesoscale circulation using different initialization methods in an operational-like context.…”

“…where HFR measurements can be used as a consistent ground-truth dataset for validation purposes and for increasing the spatial resolution of the AIS-reconstructed fields at coastal areas. The integration of HFR measurements with other multi-platform surface current data assimilation have demonstrated to improve the model performance in many studies (Paduan and Shulman, 2004;Barth et al, 2008;Hernández-Lasheras et al, 2021). Furthermore, the HFR standard data distribution in near real-time throughout the main European marine data portals, facilitating the data access and ensuring the timeliness, make them an ideal dataset for efficient data assimilation in operational modelling (Capet et al, 2020).…”

“…Furthermore, the HFR standard data distribution in near real-time throughout the main European marine data portals, facilitating the data access and ensuring the timeliness, make them an ideal dataset for efficient data assimilation in operational modelling (Capet et al, 2020). However, WMOP is the only one regional operational model from the Mediterranean, which is systematically assimilating HFR data (Hernández-Lasheras et al, 2021).…”