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| Titel |
Studying climate impacts on hydrophysical processes in Lake Constance by 3D hydrodynamic modelling |
| VerfasserIn |
Bernd Wahl, Frank Peeters |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250078469
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| Zusammenfassung |
| A 3D hydrodynamic model was applied to investigate the implications of a change in climatic
conditions for the hydrophysical behaviour of deep Upper Lake Constance. The model
simulations covered the period from 1960 to 2011. Model adaptation and verification was
based on 51 years of vertically resolved temperature recordings. Three different
horizontal grid layouts were employed to test the sensitivity of the model to spatial grid
resolution. Effective vertical turbulent diffusivities Kz in the stratified lake below 10
m were determined from simulation results and from vertically highly resolved
CTD probe data over 16 years using the heat budget method. The Kz obtained
from the simulated and measured water temperatures agreed rather well and ranged
in the order of 10-5 to 10-4Â m2s-1. In the deep water, where the lake basin is
resolved only by few grid cells, the diffusivity values were overestimated by the
model, whereby the deviation from the measurement data based estimates decreased
with increasing grid resolution. The open water turbulent diffusivities in the model
are substantially smaller than the basin wide effective diffusivities supporting that
vertical transport in a stratified lake is largely dominated by turbulent mixing near
the lake boundaries. The model was finally applied to investigate the impact of
changed wind velocities and air temperatures on deep water renewal which is a key
process for the vertical transport of nutrients and oxygen in deep Lake Constance.
Numerical tracers were employed as indicators of the vertical transport and mixing of
water. Increased air temperatures not only resulted in an overall increase in water
temperatures but also in a change of the mixing dynamics. Deep-water renewal was most
sensitive to changes in air temperatures during the winter season. Variations in
wind velocity influenced water temperatures and mixing via changes in latent and
sensible heat fluxes as well as by changes in the energy flux to turbulent motions. |
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