Particle tracking in the vicinity of Helgoland No

Authors: Ulrich Callies Andreas Plüß Jens Kappenberg Hartmut Kapitza

Publish Date: 2011/08/07

Volume: 61, Issue: 12, Pages: 2121-2139

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Abstract

Station Helgoland Roads in the southeastern North Sea German Bight hosts one of the richest longterm time series of marine observations Hydrodynamic transport simulations can help understand variability in the local data brought about by intermittent changes of water masses The objective of our study is to estimate to which extent the outcome of such transport simulations depends on the choice of a specific hydrodynamic model Our basic experiment consists of 3377 Lagrangian simulations in timereversed mode initialized every 7 h within the period Feb 2002–Oct 2004 Fiftyday backward simulations were performed based on hourly current fields from four different hydrodynamic models that are all well established but differ with regard to spatial resolution dimensionality 2D or 3D the origin of atmospheric forcing data treatment of boundary conditions presence or absence of baroclinic terms and the numerical scheme The particletracking algorithm is 2D fields from 3D models were averaged vertically Drift simulations were evaluated quantitatively in terms of the fraction of released particles that crossed each cell of a network of receptor regions centred at the island of Helgoland We found substantial systematic differences between drift simulations based on each of the four hydrodynamic models Sensitivity studies with regard to spatial resolution and the effects of baroclinic processes suggest that differences in model output cannot unambiguously be assigned to certain model properties or restrictions Therefore multimodel simulations are needed for a proper identification of uncertainties in longterm Lagrangian drift simulationsWe gratefully acknowledge the provision of output from the model BSHcmod by our colleagues from the Bundesamt für Seeschifffahrt und Hydrographie BSH in Hamburg Levitus NODC WOA98 salinity data were provided by the NOAA/OAR/ESRL PSD Boulder Colorado USA from their web site at http//wwwesrlnoaagov/psd/ For graphical display we used the Generic Mapping Tools software GMT available from wwwsoesthawaiiedu/gmt/ The study was conducted within the framework of the WIMO project Scientific monitoring concepts for the German Bight jointly funded by Niedersächsisches Ministerium für Wissenschaft und Kultur MWK and Niedersächsisches Ministerium für Umwelt und Klimaschutz MUK

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