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A simplified atmospheric boundary layer model for an improved representation of air–sea interactions in eddying oceanic models: implementation and first evaluation in NEMO (4.0)
Ist Teil von
Geoscientific Model Development, 2021-01, Vol.14 (1), p.543-572
Ort / Verlag
Katlenburg-Lindau: Copernicus GmbH
Erscheinungsjahr
2021
Quelle
EZB Electronic Journals Library
Beschreibungen/Notizen
A simplified model of the atmospheric boundary layer (ABL)
of intermediate complexity between a bulk parameterization and a three-dimensional
atmospheric model is developed and integrated to the Nucleus for European Modelling of the Ocean (NEMO) general circulation model.
An objective in the derivation of such a simplified model, called ABL1d, is
to reach an apt representation in ocean-only numerical simulations of some of the
key processes associated with air–sea interactions at the characteristic scales of
the oceanic mesoscale. In this paper we describe the formulation of the
ABL1d model and the strategy to constrain this model with large-scale
atmospheric data available from reanalysis or real-time forecasts. A particular
emphasis is on the appropriate choice and calibration of a turbulent closure scheme
for the atmospheric boundary layer. This is a key ingredient to properly represent
the air–sea interaction processes of interest. We also provide a detailed description
of the NEMO-ABL1d coupling infrastructure and its computational efficiency.
The resulting simplified model is then tested for several boundary-layer regimes
relevant to either ocean–atmosphere or sea-ice–atmosphere coupling. The coupled
system is also tested with a realistic 0.25∘ resolution global configuration.
The numerical results are evaluated using standard metrics
from the literature to quantify the wind–sea-surface-temperature
(a.k.a. thermal feedback effect),
wind–current (a.k.a. current feedback effect), and ABL–sea-ice couplings.
With respect to these metrics, our results show very good agreement with observations
and fully coupled ocean–atmosphere models for a computational overhead of about
9 % in terms of elapsed time compared to standard uncoupled simulations.
This moderate overhead, largely due to I/O operations, leaves room for further
improvement to relax the assumption of horizontal homogeneity behind ABL1d
and thus to further improve the realism of the coupling while keeping the flexibility
of ocean-only modeling.