Parameter sensitivity of a coupled atmosphere-ocean model |
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Authors: | S L Weber |
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Institution: | (1) Royal Netherlands Meteorological Institute (KNMI), P.O. Box 201, 3730 AE De Bilt, The Netherlands E-mail: weber@knmi.nl, NL |
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Abstract: | The sensitivity of a coupled model to the oceanic vertical diffusion coefficient κ
v
is examined. This is compared to the sensitivity of an ocean-only model forced by mixed boundary conditions (BC). The atmospheric
component of the coupled model is a moist energy balance model. The ocean component is a 12-level geostrophic model, defined
on a midlatitude β-plane. Atmosphere and ocean are coupled through the fluxes of heat and moisture at their interface. The
coupled model contains a number of feedback processes which are not represented in the ocean-only model. This results in a
temperature and salinity response to κ
v
which is stronger in the coupled model than in the ocean-only model. On the other hand, there is a weaker response in oceanic
processes such as meridional heat transport, deep-water formation at high latitudes, etc. Ocean-only sensitivity experiments
were also performed with modified BCs, which parametrise the feedback processes included in the coupled model. These are the
modified thermal BC of Rahmstorf and Willebrand and a modified freshwater BC proposed in the present study. Large-scale features
of the response in oceanic surface fields are well represented with modified BCs. However, the sensitivity of the deep ocean
temperature is only partly captured due to local differences in the surface response. The scaling behavior of the zonal overturning
stream function was found to depend on the surface BCs. In contrast to this, the meridional overturning stream function basically
scales with κ0.5
v
in all sensitivity experiments. Differences in the heat transport response among the experiments are thus primarily related
to differences in the temperature response.
Received: 28 February 1997/Accepted: 12 September 1997 |
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Keywords: | |
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