Water circulation forecasting in Spanish harbours

Abstract

SUMMARY: This paper describes the first harbour circulation forecasting system implemented in Spain. The configuration design was based on previous analyses of the morphologic and hydrodynamic behaviour of three harbours: Barcelona, Tarragona and Bilbao. A nested system of oceanic models was implemented, with a scope ranging from the regional scale (with a mean horizontal resolution of 5 km) to the harbour scale (with a mean horizontal resolution of 40 m). A set of sensitivity tests was carried out in order to determine the optimal configurations. The results of the operational system were compared with available observations, revealing that the intermediate models are able to reproduce the averaged hydrodynamic behaviour but not the spatio-temporal variability. With the harbour models the quality of the forecasts improves, reaching a correlation and RMSE of ~0.6 and 6 cm s -1 , respectively, for Bilbao harbour. In addition, numerical experiments were carried out to evaluate the sensitivity of the forecasts to error sources. The results suggest that the errors in the information prescribed in the lateral boundary conditions are the most influential in the quality of the predictions. Errors in the wind field also have a smaller but non-negligible influence. Although the system is in the initial implementation phase and should be improved upon in the future, it is now a useful tool for harbour management. The predictions will be very helpful for harbour operations, pollution risk management and fighting oil spills.Keywords: operational oceanography, harbour hydrodynamics, Barcelona harbour, Bilbao harbour, Tarragona harbour. RESUMEN: Predicción de la circulación marina en los Puertos esPañoles. -En este artículo se describe el primer sistema operacional de predicción de la circulación en puertos implementado en España. El diseño del sistema se ha basado en un análisis previo de las características hidrodinámicas y morfológicas de tres puertos de estudio: Barcelona, Tarragona y Bilbao. Se ha establecido un sistema de modelos oceánicos anidados que cubre desde la escala regional (con una resolución media horizontal de 5 km) al dominio portuario (con una resolución de 40 m). Diferentes experimentos de sensibilidad se han llevado a cabo para determinar las configuraciones óptimas. Los resultados del sistema operacional se han comparado con las observaciones disponibles, mostrando que los modelos intermedios son capaces de resolver el comportamiento hidrodinámico promedio, pero no la variabilidad espacio-temporal. En cuanto a los modelos portuarios, la calidad de las predicciones mejora, alcanzando una correlación y un RMSE de ~0.6 y 6 cm s -1 , respectivamente, para el puerto de Bilbao. Adicionalmente se han realizado diferentes experimentos para determinar la sensibilidad del sistema a distintas fuentes de error. Los resultados sugieren que los errores en las condiciones de contorno laterales son los más determinantes sobre la calidad de las predicciones portuarias. Los errores en el viento, aun siendo menos importan...

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

“…The spectral nudging aims at forcing the regional child model solution (IBI) to be close to the parent system (GLOBAL) in those areas where the latter is supposed to be accurate thanks to data assimilation, mainly in deep waters outside the continental shelf (Herbert et al, 2014). After each forecast cycle of IBI, the increment between the parent model analysis X p and the child model forecast X c is calculated for a chosen state variable X (typically currents, temperature, and salinity).…”

“…where there is no data assimilation of altimetry or where the physics is missing, for instance on the shelf) or where the spatial filtering processes are potentially detrimental (close to the bottom or the open boundaries). This spatial weight function is a 3-D mask (for further details, see Herbert et al, 2014) that differentiates the zones where IBI system is nudged and thus reconciled with the parent system (typically in the open sea) from those where IBI remains free (continental shelf, coastal areas, and regions close to the open boundaries) to fully compute higher-frequency processes such as thermal tidal fronts, river discharges, etc.…”

“…Therefore, this approach implies the transfer of large-scale information from the global model to the interior of the nested regional domain by means of diverse methodologies. One of them is the so-called "spectral nudging" technique, adopted to ensure that the prevailing global conditions are not degraded in the open ocean, while allowing submesoscale processes to be resolved exclusively by the nested model in the continental shelf and coastal areas (Herbert et al, 2014). An alternative approach to computational time-demanding multiple nesting procedures consists of using unique unstructured grid models as they have proved to properly describe ocean processes at different spatial scales (Ferrarin et al, 2013(Ferrarin et al, , 2019Federico et al, 2017;Cucco et al, 2012).…”

“…Despite the recent advances in the development of CMEMS global and regional core products, many downstream services for user uptake require information on even smaller spatial scales, such as ocean forecasting for small island chains (Caldeira et al, 2016), intricate bights (Stanev et al, 2016), or port approach areas where sharp topobathymetric gradients pose special difficulties for accurate local predictions (Hlevca et al, 2018;Federico et al, 2017;Sánchez-Arcilla et al, 2016;Sammartino et al, 2014;Grifoll et al, 2012). A variety of operational products for harbours have been recently developed, although most of these coastal applications are wave and water-level forecasting sys-tems (Lin et al, 2008;Pérez et al, 2013).…”

Crucial times for Spanish physical oceanography

“…They also exemplify the three main types of Spanish institutions that carry on research in physical oceanography: universities, research centres and governmental organizations. Bastida et al (2012) examine the processes leading to mixing episodes within the bottom boundary layer of a shelf area and Grifoll et al (2012) assess the sensitivity of a forecasting system for harbours which includes the nesting of several ocean models. Peña-Izquierdo et al (2012) use field data to give an exhaustive description of the complex current system over the continental slope off NW Africa, Mason et al (2012) use numerical results to discuss the origin and spatio-temporal variability of the African upwelling north of the Canary Islands, and Delgado et al (2012) (2012) use field data to evaluate the performance of several wind-drag parameterizations for mixed sea conditions.…”