Tidal and wind-driven surface currents in the German Bight: HFR observations versus model simulations

Port, Alexander; Gurgel, Klaus-Werner; Staneva, Joanna; Schulz‐Stellenfleth, Johannes; Stanev, Emil V.

doi:10.1007/s10236-011-0412-9

Cited by 36 publications

(41 citation statements)

References 38 publications

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“…With their large area coverage, high resolution in time and space, and long-term operational capabilities, the radar systems have enhanced the coastal ocean monitoring capabilities for surface currents (Paduan and Rosenfeld, 1996) and have enabled the development of new data products. The value of HF radar data for the investigation of circulation in the German Bight was demonstrated by Carbajal and Pohlmann (2004) and Port et al (2011). Currently, an observation network of three Wellen radars (WERAs) in the German Bight operates as part of the COSYNA preoperational system (see Fig.…”

Section: The Variables Of Interest For Coastal Applications Includementioning

confidence: 94%

Ocean forecasting for the German Bight: from regional to coastal scales

Stanev¹,

Schulz‐Stellenfleth²,

Staneva³

et al. 2016

Ocean Sci.

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Abstract. This paper describes recent developments based on advances in coastal ocean forecasting in the fields of numerical modeling, data assimilation, and observational array design, exemplified by the Coastal Observing System for the North and Arctic Seas (COSYNA). The region of interest is the North and Baltic seas, and most of the coastal examples are for the German Bight. Several pre-operational applications are presented to demonstrate the outcome of using the best available science in coastal ocean predictions. The applications address the nonlinear behavior of the coastal ocean, which for the studied region is manifested by the tidal distortion and generation of shallow-water tides. Led by the motivation to maximize the benefits of the observations, this study focuses on the integration of observations and modeling using advanced statistical methods. Coastal and regional ocean forecasting systems do not operate in isolation but are linked, either weakly by using forcing data or interactively using two-way nesting or unstructured-grid models. Therefore, the problems of downscaling and upscaling are addressed, along with a discussion of the potential influence of the information from coastal observatories or coastal forecasting systems on the regional models. One example of coupling coarse-resolution regional models with a fineresolution model interface in the area of straits connecting the North and Baltic seas using a two-way nesting method is presented. Illustrations from the assimilation of remote sensing, in situ and high-frequency (HF) radar data, the prediction of wind waves and storm surges, and possible applications to search and rescue operations are also presented. Concepts for seamless approaches to link coastal and regional forecasting systems are exemplified by the application of an unstructured-grid model for the Ems Estuary.

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Section: The Variables Of Interest For Coastal Applications Includementioning

confidence: 94%

Ocean forecasting for the German Bight: from regional to coastal scales

Stanev¹,

Schulz‐Stellenfleth²,

Staneva³

et al. 2016

Ocean Sci.

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“…9a and e). For this region, Port et al (2011) identified a higher variability of surface currents, less correlated with wind conditions, which would imply that introducing either Stokes drift or an additional wind drag could probably be a less promising approach for model improvement. However, still the most probable explanation for the mismatch of observations and corresponding simulations is that the drifter experienced problems with its drogue.…”

Section: Discussionmentioning

confidence: 99%

Surface drifters in the German Bight: model validation considering windage and Stokes drift

et al. 2017

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Abstract. Six surface drifters (drogued at about 1 m depth) deployed in the inner German Bight (North Sea) were tracked for between 9 and 54 days. Corresponding simulations were conducted offline based on surface currents from two independent models (BSHcmod and TRIM). Inclusion of a direct wind drag (0.6 % of 10 m wind) was needed for successful simulations based on BSHcmod currents archived for a 5 m depth surface layer. Adding 50 % of surface Stokes drift simulated with a third-generation wave model (WAM) was tested as an alternative approach. Results resembled each other during most of the time. Successful simulations based on TRIM surface currents (1 m depth) suggest that both approaches were mainly needed to compensate insufficient vertical resolution of hydrodynamic currents.The study suggests that the main sources of simulation errors were inaccurate Eulerian currents and lacking representation of sub-grid-scale processes. Substantial model errors often occurred under low wind conditions. A lower limit of predictability (about 3-5 km day −1 ) was estimated from two drifters that were initially spaced 20 km apart but converged quickly and diverged again after having stayed at a distance of 2 km or less for about 10 days. In most cases, errors in simulated 25 h drifter displacements were of similar order of magnitude.

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“…The recent progress due to intercomparisons between observations and numerical modelling (Staneva et al, 2009) is currently extended in COSYNA activities towards more profound regional analyses (Port et al, 2011) and data assimilation (SchulzStellenfleth et al, 2011). More details on the characteristic circulation features can be found in the above mentioned papers.…”

Section: Numerical Modelsmentioning

confidence: 99%

“…A number of studies demonstrated that valuable information about small scale hydrodynamic processes can be gathered by statistical analysis of HF radar measurements (e.g., Gough et al, 2010;Prandle, 1987;Port et al, 2011). Another promising application of HF radar data is the assimilation in numerical models in order to improve ocean forecasts.…”

Section: Reconstruction Of Tidal Currents Based On Radial Component Mmentioning

confidence: 99%

Coastal observing and forecasting system for the German Bight – estimates of hydrophysical states

et al. 2011

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Abstract.A coastal observing system for Northern and Arctic Seas (COSYNA) aims at construction of a long-term observatory for the German part of the North Sea, elements of which will be deployed as prototype modules in Arctic coastal waters. At present a coastal prediction system deployed in the area of the German Bight integrates near real-time measurements with numerical models in a preoperational way and provides continuously state estimates and forecasts of coastal ocean state. The measurement suite contributing to the pre-operational set up includes in situ time series from stationary stations, a High-Frequency (HF) radar system measuring surface currents, a FerryBox system and remote sensing data from satellites. The forecasting suite includes nested 3-D hydrodynamic models running in a dataassimilation mode, which are forced with up-to-date meteorological forecast data. This paper reviews the present status of the system and its recent upgrades focusing on developments in the field of coastal data assimilation. Model supported data analysis and state estimates are illustrated using HF radar and FerryBox observations as examples. A new method combining radial surface current measurements from a single HF radar with a priori information from a hydrodynamic model is presented, which optimally relates tidal ellipses parameters of the 2-D current field and the M2 phase and magnitude of the radials. The method presents a robust and helpful first step towards the implementation of a more sophisticated assimilation system and demonstrates that even using only radials from one station can substantially benefit state estimates for surface currents. Assimilation of FerryBox data based on an optimal interpolation approach using a Kalman filter with a stationary background covariance maCorrespondence to: E. V. Stanev (emil.stanev@hzg.de) trix derived from a preliminary model run which was validated against remote sensing and in situ data demonstrated the capabilities of the pre-operational system. Data assimilation significantly improved the performance of the model with respect to both SST and SSS and demonstrated a good skill not only in the vicinity of the Ferry track, but also over larger model areas. The examples provided in this study are considered as initial steps in establishing new coastal ocean products enhanced by the integrated COSYNA-observations and numerical modelling.

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Tidal and wind-driven surface currents in the German Bight: HFR observations versus model simulations

Cited by 36 publications

References 38 publications

Ocean forecasting for the German Bight: from regional to coastal scales

Ocean forecasting for the German Bight: from regional to coastal scales

Surface drifters in the German Bight: model validation considering windage and Stokes drift

Coastal observing and forecasting system for the German Bight – estimates of hydrophysical states

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