Skill assessment of global, regional, and coastal circulation forecast models: evaluating the benefits of dynamical downscaling in IBI (Iberia–Biscay–Ireland) surface waters

Abstract

Abstract. In this work, a multi-parameter inter-comparison of diverse ocean forecast models was conducted at the sea surface ranging from global to local scales in a two-phase stepwise strategy. Firstly, a comparison of CMEMS GLOBAL and the nested CMEMS IBI regional system was performed against satellite-derived and in situ observations. Results highlighted the overall benefits of both the GLOBAL direct data assimilation in open water and the increased horizontal resolution of IBI in coastal areas. Besides, IBI (Iberia–Biscay–Ireland) proved to capture shelf dynamics by better representing the horizontal extent and strength of a river freshwater plume, according to the results derived from the validation against in situ observations from a buoy moored in NW Spain. Secondly, a multi-model inter-comparison exercise for 2017 was performed in the Strait of Gibraltar among GLOBAL, IBI, and SAMPA (Sánchez-Garrido et al., 2013) high-resolution coastal forecast systems (partially nested to IBI) in order to elucidate the accuracy of each system to characterize the Atlantic Jet (AJ) inflow dynamics. A quantitative validation against hourly currents from high-frequency radar (HFR) highlighted both the steady improvement in AJ representation in terms of speed and direction when zooming from global to coastal scales through a multi-nesting model approach and also the relevance of a variety of factors at local scale such as a refined horizontal resolution, a tailored bathymetry, and a higher spatio-temporal resolution of the atmospheric forcing. The ability of each model to reproduce a 2 d quasi-permanent full reversal of the AJ surface inflow was examined in terms of wind-induced circulation patterns. SAMPA appeared to better reproduce the reversal events detected with HFR estimations, demonstrating the added value of imposing accurate meteorologically driven barotropic velocities in the open boundaries (imported from the NIVMAR (Álvarez-Fanjul et al., 2001) storm surge model) to take into account the remote effect of the atmospheric forcing over the entire Mediterranean basin, which was only partially included in IBI and GLOBAL systems. Finally, SAMPA coastal model outputs were also qualitatively analysed in the western Alboran Sea to put in a broader perspective the context of the onset, development, and end of such flow reversal episodes.

Comparative Analysis of Summer Upwelling and Downwelling Events in NW Spain: A Model-Observations Approach

“…This is particularly true in the NW Iberian waters, where coastal meanders and migratory eddies have been documented to exist and have ecological implications as nutrient conveyors [70,71]. In this context, previous studies demonstrated that small-scale coastal processes are poorly reproduced (or even misrepresented) in coarser grid meshes, suggesting the strong necessity of finer horizontal resolution in both hydrodynamic models [72] and HFR systems [46] to properly capture such littoral phenomena. Since this topic remains open and disputable, further investigations should be conducted to shed light on it.…”

Modelling the marine ecosystem of Iberia–Biscay–Ireland (IBI) European waters for CMEMS operational applications

“…The model includes the atmospheric dust deposition of Fe, Si, P and N at the ocean surface (Aumont et al, 2015). River discharge of nutrients comes from the Global NEWS 2 datasets (Mayorga et al, 2010) and carbon comes from Ludwig et al (1996). An iron source corresponding to sediment reductive mobilisation on continental margins is also considered.…”

“…These regional coupled systems, and of course the 1/4 • NEMO-PISCES global ocean operational system, are the subject of intercomparisons. Ocean dynamics forecast models, all of them based on NEMO, are already being compared in Lorente et al (2019) and Mason et al (2019). For the marine biogeochemistry and ecosystem dynamics, intercomparison is initiated in the framework of CMEMS but represents a significant work because the biogeochemical models differ in complexity .…”

Evaluation of the Operational CMEMS and Coastal Downstream Ocean Forecasting Services During the Storm Gloria (January 2020)

“…Combining enhanced high-frequency ocean observations, such as high-frequency (HF) radar currents, and different operational model products, Lin et al (2016) assessed an operational system at the Taiwan strait whose bias compared with HF-radar was close to -0.07 m/s under a calm regime; but double it (around 0.15 m/s) during typhoons Sinlaku (2008) and Morakot (2009). Likewise, Lorente et al (2019b), takes advantage of a long-term coverage of HF-Radar surface currents in the Gibraltar Strait area to provide a deeper analysis on the surface Atlantic jet variability. This work demonstrated the steady model improvement, when moving from global to coastal scales through a multi-nesting approach.…”