Ocean Modelling in Support of Operational Ocean and Coastal Services

Operational oceanography is maturing rapidly. Its related capabilities are being noticeably enhanced in response to a growing demand for regularly updated ocean information. Today, several core forecasting and monitoring services, focused on global and regional scales, are well established. The sustained availability of their products has favored the proliferation of downstream services devoted to coastal monitoring and forecasting. Ocean models (together with proliferation in the use of data-assimilation schemes to generate analysis) are key components in operational oceanographic systems, as ocean modeling drives the evolution of services (especially in a context marked by the extensive application of dynamic downscaling approaches for coastal applications).

The goal of this Special Issue was to publish research focused on ocean modeling to benefit model applications and support existing operational oceanographic services. Likewise, research works focused on improving combinations of ocean models with observational products, including data assimilation, were also considered, as well as papers addressing model product quality assessments and evaluations of operational service capabilities to simulate outstanding marine processes/features and extreme events.

The book “Ocean Modelling in Support of Operational Ocean and Coastal Services” includes eleven contributions [1,2,3,4,5,6,7,8,9,10,11] to this Special Issue published during 2021–2022. The overall objective of this Special Issue is to draw an updated picture of the heterogeneous challenges that are being addressed in operational oceanographic regional and coastal services, gathering novel and cutting-edge techniques and methods to advance the state of the art of forecast and analysis products. The scientific collection presented in this Special Issue will be valuable for both scientists/technical developers and end-users, since each paper within is motivated by an applied and pragmatic spirit, with the objective of providing better and more fit-for-purpose ocean model solutions (from a widespread set of applications) that meet a growing number of end-user requirements and needs.

Considering the eleven different contributions presented in this Special Issue, it is possible to highlight five major goals or thematic groups that seem to articulate them:

• Ocean model improvements to support better (or new) operational forecasting [2,5,7,9,10];
• Increasing interactions between systems (including contributions to the river hydrological system), improving data forcing and promoting coupling approaches [3,6,7,9,10,11];
• Data assimilation progress (towards better analysis products) [7,8,10];
• Enhancing product quality assessment and demonstrating downscaling’s added value [2,8,9,10].
• New approaches to improve/optimize specific components in operational services [1,4,11].

A brief overview of all the contributions follows, emphasizing the main investigation topic and the outcome of the analysis.

Some of the contributions are related to new services or developments achieved in the context of the Copernicus Marine Regional Monitoring and Forecasting Services.

Ciliberti et al. [7] describe the latest developments in the context of the Copernicus Marine Black Sea Monitoring and Forecasting Center to improve the skill of their ocean analyses, forecasts, and re-analyses (for hydrodynamics, biogeochemistry, and waves). Model solutions are generated through a set of dedicated online coupled systems which involve physics, biogeochemistry, and waves, together with the atmosphere. A special focus on the physical component of this regional Black Sea Copernicus Marine service is provided by Ciliberti et al. [8], including insight for the ocean model and data assimilation scheme used, as well as details on the operational quality assessment framework. On the European–Atlantic side, Toledano et al. [10] show the most recent advances of the new Copernicus Marine regional IBI wave forecast service, emphasizing the impacts that both a new altimetric wave data assimilation scheme and current–wave coupling have on operational wave products. The demonstrated benefits, related to the herein proposed upgrades, supported the IBI-MFC decision to evolve its operational wave system, using (since the March 2020 Copernicus Marine Release) the resulting wave model set-up, with data assimilation and current–wave coupling for operational purposes.

Some other contributions are focused on new services implemented at national or local coastal levels, with modelling applications covering sites of specific interest. Thus, García-León et al. [9] show the most recent developments applied to the SAMOA forecast service deployed for 31 Spanish ports. Research was focused on upgrading the ROMS model set-up, together with atmospheric forcing and the testing of new methodologies to nest the SAMOA system into the Copernicus Marine IBI-MFC regional solution (with emphasis on its 3D hourly dataset). Model sensitivity tests were extensively assessed using the available in situ and remote sensed (including RadarHF) observations, demonstrating the added value of the downscaled coastal solutions. Ilicak et al. [5] simulate the Turkish Strait System, connecting the Black Sea and the Mediterranean using a model of the Turkish strait system using a high-resolution unstructured grid ocean circulation model, with realistic atmospheric forcing and lateral open-boundary conditions from the Copernicus Marine system. Nagy et al. [2] illustrate the main achievements associated with the development and validation of a new operational model system for an area of the northeast Atlantic that encompasses all of Ireland’s territorial waters. The system, based on an ROMS application, uses operationally available atmospheric and boundary forcing, tidal forcing, and a climatological river contribution. Some insights on the skill of the systems are provided, compared with in situ and satellite observations, and specific studies on the simulation of the Irish coastal current are provided.

New approaches to improve/optimize specific components of operational services are also included in the Special Issue: Yang et al. [4] propose a barotropic solver for high-resolution ocean general circulation models that helps to ensure scalability and the optimization of performance. The new algorithm proposed was tested on the NEMO ocean model, allowing good scalability and significant computational execution time reductions. Yuan et al. [1] aim to use singular spectrum analysis (SSA) to reduce the noise level in Jason-1 altimeter waveforms in order to obtain SSA-denoised waveforms, and thus improve the accuracy of a mean sea surface height (MSSH) model. This methodology can help to reduce the contamination of altimeter waveforms (usually due to nonmarine surfaces or inhomogeneous sea-state conditions). Model accuracy enhancements over the China Sea are obtained using SSA-denoised waveforms, compared with those for raw waveforms.

Related to the increase in interactions between systems, improving uses of data forcing, and promoting coupling approaches, Causio et al. [6] study wave–current interaction for the first time in the Black Sea, implementing a coupled numerical system based on NEMO and WaveWatchIII, evaluating how waves impact surface ocean dynamics, and how ocean currents may impact sea state. Different physical processes are considered in the study (i.e., Stokes–Coriolis force, sea-state-dependent momentum flux, wave-induced vertical mixing, Doppler shift effect, and stability parameter for the computation of effective wind speed).

Finally, with respect to the inclusion of a contribution regarding the river hydrological system, Campuzano et al. [11] aim to explore the potential impacts on the ocean system that can be obtained by using sophisticated land boundary conditions based on the capacities of state-of-the-art hydrologic models combined with observation networks. Together with the assessment of the source of river-flow data, this work also explores the use of estuarine proxies based on simple modelling grids. The estuarine proxies enable the incorporation of the mixing processes that take place in estuaries into the land fluxes, and obtain plume momentum. The watershed, estuarine proxies, and ocean were modelled using the MOHID water modelling system and evaluated in Western Iberia waters (illustrating the sea surface salinity extension of the Western Iberia Buoyant Plume during an extreme event). Sotillo et al. [3] analyses the river freshwater contribution of the European Atlantic margin and its influence on the sea salinity field by means of model sensitivity tests. The paper assesses the potential impacts that newly available river discharge datasets can have on regional ocean model solutions delivered by the Copernicus Marine IBI-MFC regional service when used as part of the freshwater land forcing. Usages of these data result in a better capture of salinity variability and a more realistic simulation of baroclinic frontal structures linked to coastal and river freshwater buoyancy plumes; major impacts are found in areas with bigger river discharge contributions (i.e., the French shelf or the northwestern Iberian coast).