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Environ Fluid Mech (2008) 8:349366
DOI 10.1007/s10652-008-9101-8
ORIGINAL ARTICLE
Georgiy Kirillin Christof Engelhardt
Sergey Golosov
Received: 20 March 2008 / Accepted: 23 August 2008 / Published online: 16 September 2008 Springer Science+Business Media B.V. 2008
Abstract A mesoscale vortex structure in the small stratied Lake Stechlin has been revealed by eld experiments with satellite-tracked quasi-lagrangian drifters. The vortex with a radius of about 200m drifted at 300m/day along the western bight of the lake with nearly constant rotation speed of 3cpd. Analysis of kinematical properties of the vortex motion demonstrates solid body character of rotation. Extrapolation of the vortex drift trajectory over the period preceding the observations combined with data on local winds and seiche dynamics has allowed tracing the vortex fate from its generation point. The normal modes analysis of the internal seiching in the lake reveals the vortex generation mechanism to be the interaction of certain seiche modes with local bottom topography and suggests generation of the mesoscale vortices to be the a regular feature of the lake circulation. Analysis of vorticity suggests additional energy supply to rotational ow, possibly from inverse cascading of small-scale turbulent motionsa feature typical for quasi-2D turbulence. The vortices can play an important role in the energy transport from basin-scale motions to small-scale boundary mixing. They can also contribute significantly to the horizontal heterogeneity of phyto- and zooplankton distribution as well as to the transport of dissolved matter such as nutrients between littoral and profundal areas. The topographically generated traveling vortices represent an analog of the synoptic eddies in the Ocean and in the Atmosphere, whereas their role in the lake hydrodynamics is practically unknown.
Keywords Lake circulation Lagrangian Drifters GPS buoys Coherent vortices
Mesoscale eddies
G. Kirillin (B) C. Engelhardt S. Golosov
Department of Ecohydrology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Mggelseedamm 310, 12587 Berlin, Germanye-mail: [email protected]: www.igb-berlin.de/abt1/mitarbeiter/kirillin/index_e.shtml
A mesoscale vortex in a small stratied lake
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1 Introduction
Mesoscale synoptic eddies (vortices) are known to be an essential energy transport mechanism in the lower atmosphere; they are also recognized as an important feature of the ocean circulation [13,18]. In the atmosphere and ocean dynamics, the Coriolis force is the fundamental mechanism supporting the rotational coherent structure of the vortices...