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| Titel |
Using an atmospheric boundary layer model to force global ocean models |
| VerfasserIn |
Rafael Abel, Claus Böning |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250094402
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| Publikation (Nr.) |
 EGU/EGU2014-9810.pdf |
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| Zusammenfassung |
| Current practices in the atmospheric forcing of ocean model simulations can lead to
unphysical behaviours. The problem lies in the bulk formulation of the turbulent air-sea
fluxes in the conjunction with a prescribed, and unresponsive, atmospheric state (as given by
reanalysis products). This can have impacts both on mesoscale processes as well as on the
dynamics of the large-scale circulation. First, a possible local mismatch between the given
atmospheric state and evolving sea surface temperature (SST) signatures can occur, especially
for mesoscale features such as frontal areas, eddies, or near the sea ice edge. Any ocean front
shift or evolution of mesoscale anomalies results in excessive, unrealistic surface fluxes due
to the lack of atmospheric adaptation. Second, a subtle distortion in the sensitive balance of
feedback processes being critical for the thermohaline circulation. Since the bulk
formulations assume an infinite atmospheric heat capacity, resulting SST anomalies are
strongly damped even on basin-scales (e.g. from trends in the Atlantic meridional overturning
circulation). In consequence, an important negative feedback is eliminated, rendering the
system excessively susceptible to small anomalies (or errors) in the freshwater
fluxes.
Previous studies (Seager et al., 1995, J. Clim.) have suggested a partial forcing issue
remedy that aimed for a physically more realistic determination of air-sea fluxes by allowing
some (thermodynamic) adaptation of the atmospheric boundary layer to SST changes.
In this study a modernized formulation of this approach (Deremble et al., 2013,
Mon. Weather Rev.; ’CheapAML’) is implemented in a global ocean-ice model with
moderate resolution (0.5°; ORCA05). In a set of experiments we explore the solution
behaviour of this forcing approach (where only the winds are prescribed, while
atmospheric temperature and humidity are computed), contrasting it with the solution
obtained from the classical bulk formulation with a non-responsive atmosphere. |
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