Modelling surface drifting of buoys during a rapidly-moving weather front in the Gulf of Finland, Baltic Sea

Gästgifvars, Maria; Lauri, Hannu; Sarkanen, Annakaisa; Myrberg, Kai; Andrejev, Oleg; Ambjörn, Cecilia

doi:10.1016/j.ecss.2006.06.010

Cited by 36 publications

(21 citation statements)

References 8 publications

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“…In several other studies (e.g. Gästgifvars et al, 2006;Kjellsson and Döös, 2012;De Dominicis et al, 2012), simulated marine surface currents were found to be too small, possibly also due to insufficient resolution of the marine surface layer. As a side effect, predictions may be particularly good when marine currents and winds are nearly parallel (Gästgif-vars et al, 2006).…”

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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Section: Discussionmentioning

confidence: 99%

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

et al. 2017

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“…The problem is even more complicated in strongly stratified sea areas such as the Gulf of Finland where the drift is frequently steered by multi-layered dynamics (Andrejev et al 2004;Gästgifvars et al 2006) and where it is not clear beforehand which theoretical framework (predomination of 2D or 3D motion systems) should be used in the analysis.…”

Section: Discussionmentioning

confidence: 99%

“…Similar problems intrinsically arise in the attempts of modelling pathways of different water masses (Meier 2007) and especially in simulations, both in forecast and hindcast modes, of pollution transport by regional ocean models such as HIROMB or Seatrack Web (Funkquist 2001;Gästgifvars et al 2006;Verjovkina et al 2010). This chapter has contributed by presenting results from recently deployed surface drifters of different types as well as drifters simulated with an ocean model and a trajectory code, and comparing these to each other and the theoretical expectations and discussing the implications for Lagrangian modelling in the Baltic Sea.…”

Section: Discussionmentioning

confidence: 99%

Evaluation and Tuning of Model Trajectories and Spreading Rates in the Baltic Sea Using Surface Drifter Observations

Kjellsson

Döös

Soomere

2013

Preventive Methods for Coastal Protection

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Results from experiments with surface drifters in the Baltic Sea in 2010-2011 are presented and discussed. In a first experiment, 12 SVP-B (Surface Velocity Program, with Barometer) drifters with a drogue at 12-18 m depth were deployed in the Baltic Sea. In a second experiment, shallow drifters extending to a depth of 1.5 m were deployed in the Gulf of Finland. Results from the SVP-B drifter experiment are compared to results from a regional ocean model and a trajectory code. Differences between the observed SVP-B drifters and simulated drifters are found for absolute dispersion (i.e., squared displacement from initial position) and relative dispersion (i.e., squared distance between two initially paired drifters). The former is somewhat underestimated since the simulated currents are neither as fast nor as variable as those observed. The latter is underestimated both due to the abovementioned reasons and due to the resolution of the ocean model.For the shallower drifters, spreading in the upper 1-2 m of the Gulf of Finland is investigated. The spreading rate is about 200 m/day for separations <0.5 km, 500 m/day for separations below 1 km and in the range of 0.5-3 km/day for separations in the range of 1-4 km. The spreading rate does not follow Richardson's law. The initial spreading, up to a distance of about d = 100-150 m, is governed by the power law d ∼ t 0.27 whereas for larger separations the distance increases as d ∼ t 2.5 .

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“…Rixen et al (2008), too, have shown that taking the combined effect of wind, currents and waves into account leads to more accurate predictions of the surface drift. In our study area, the Baltic Sea, taking into account wave conditions, has been found to improve the modelled drift of objects in some cases (Gästgifvars et al 2004).…”

Section: Introductionmentioning

confidence: 84%

Surface Stokes drift in the Baltic Sea based on modelled wave spectra

et al. 2017

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The Stokes drift is an important component in the surface drift. We used the wave model WAM to evaluate the mean values and exceedance probabilities of the surface Stokes drift in the Baltic Sea. As there is no direct way to verify the accuracy of the modelled Stokes drift, we compared the bulk parameters calculated by the wave model against buoy measurements to ensure the quality of the wave hindcast. ) and underestimate the larger values of the Stokes drift compared to the values calculated by the wave model. The modelled surface Stokes drift direction mostly followed the forcing wind direction. This was the case even in the Gulf of Finland, where the direction of the wind and the waves can differ considerably.

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Modelling surface drifting of buoys during a rapidly-moving weather front in the Gulf of Finland, Baltic Sea

Cited by 36 publications

References 8 publications

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

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

Evaluation and Tuning of Model Trajectories and Spreading Rates in the Baltic Sea Using Surface Drifter Observations

Surface Stokes drift in the Baltic Sea based on modelled wave spectra

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