Evaluation of numerical models by FerryBox and fixed platform in situ data in the southern North Sea

Abstract

Abstract. For understanding and forecasting of hydrodynamics in coastal regions, numerical models have served as an important tool for many years. In order to assess the model performance, we compared simulations to observational data of water temperature and salinity. Observations were available from FerryBox transects in the southern North Sea and, additionally, from a fixed platform of the MARNET network. More detailed analyses have been made at three different stations, located off the English eastern coast, at the Oyster Ground and in the German Bight.FerryBoxes installed on ships of opportunity (SoO) provide high-frequency surface measurements along selected tracks on a regular basis.The results of two operational hydrodynamic models have been evaluated for two different time periods: BSHcmod v4 (January 2009 to April 2012) and FOAM AMM7 NEMO (April 2011 to April 2012). While they adequately simulate temperature, both models underestimate salinity, especially near the coast in the southern North Sea. Statistical errors differ between the two models and between the measured parameters. The root mean square error (RMSE) of water temperatures amounts to 0.72 • C (BSHcmod v4) and 0.44 • C (AMM7), while for salinity the performance of BSHcmod is slightly better (0.68 compared to 1.1).The study results reveal weaknesses in both models, in terms of variability, absolute levels and limited spatial resolution. Simulation of the transition zone between the coasts and the open sea is still a demanding task for operational modelling. Thus, FerryBox data, combined with other observations with differing temporal and spatial scales, can serve as an invaluable tool not only for model evaluation, but also for model optimization by assimilation of such high-frequency observations.

Evaluation and Application of Newly Designed Finite Volume Coastal Model FESOM-C, Effect of Variable Resolution in the Southeastern North Sea

“…Comparing several models, the authors found a significant difference in a nonlinear effect within the tidal dynamics of the shallow coastal zone, which they attributed in all likelihood to coarse horizontal resolutions. An evaluation [33] of two operational models with relatively high resolutions (up to 900 m) in the North Sea region, BSHcmod v4 and FOAM AMM7 NEMO, found good agreement between the models and observations of the open sea. Near the coast however, the study found a significant deviation between simulated and observed salinity.…”

The Coastal Observing System for Northern and Arctic Seas (COSYNA)

“…The recorded variables include temperature, conductivity, salinity (derived from temperature and conductivity), chlorophyll a fluorescence, turbidity, dissolved oxygen (DO), the partial pressure of CO 2 (pCO 2 ), pH, alkalinity, nutrients, and algal groups (derived from patterns of algal fluorescence by excitation at different wavelengths). The data are used for model validation Haller et al, 2015) and assimilation studies Grayek et al, 2011;Fig. 10).…”

Long‐term intercomparison of two pCO2 instruments based on ship‐of‐opportunity measurements in a dynamic shelf sea environment

“…comm., May 2020). A past study comparing a FerryBox temperature sensor from a different ship against a fixed buoy found that the ship‐based measurements were on average 0.37°C warmer than the in situ temperatures (Haller et al 2015). While this comparison was performed for a different ship, the FerryBox installation is similar between the two ships so we can assume a similar warming inside the intake pipes of Lysbris Seaways .…”