A one-dimensional Atmospheric Boundary Layer (ABL1D) model is coupled with the NEMO ocean model and implemented over the Iberian–Biscay–Ireland (IBI) area at 1/36° resolution to investigate the ...damping effect of the current and the thermal feedback on the kinetic energy (KE) at the mesoscale. This type of coupling between an ocean model and an ABL1D is a newly proposed approach as an alternative of intermediate complexity between bulk forcing and full coupling with an atmosphere model. In ABL1D, the prognostic tracers are nudged toward large-scale variables and the wind is guided by a low-frequency geostrophic wind provided from the ERA-Interim reanalyses. First, the ABL1D is successfully validated against satellite observations regarding the wind, and the dynamic coupling coefficient (linking the near surface wind and wind-stress to the of the surface currents) are consistent with the literature, over the period 2016–2017. Our results show that the thermal feedback has a negligible impact on kinetic energy (KE) and does not influence the strength of the current feedback in the region. Given the ABL1D physics, this further indicates that the changes in the vertical wind structure caused by CFB are primarily governed by local mechanical mechanisms associated with surface wind-stress condition, rather than by thermodynamic or non-local processes within the planetary boundary layer. The induced KE reduction by the current feedback amounts to 14% at the surface and propagates down to 2000 m, indicating that it can modify the vertical distribution of KE throughout the water column. KE reductions in the surface boundary layer (0 – 300 m) and in the interior (300 – 2000 m) are attributed to a reduction of the surface wind work by 4%, and of the pressure work by 7%, respectively. The Ekman pumping anomalies induced by the current feedback tend to attenuate eddy activity and horizontal pressure gradients at depth, illustrating the potential of the current feedback to induce a geostrophic adjustment on the water column. These results illustrate the relevance of the proposed ABL1D coupling approach for reproducing the wind-current coupling (a.k.a. current feedback effect) which cannot be taken into account straightforwardly with simple bulk forcing.
•A one-dimensional Atmospheric Boundary Layer (ABL1D) model is coupled with the NEMO ocean model over the Iberian–Biscay–Ireland area.•Our model is validated against satellite data and used to study current and thermal feedback effects on kinetic energy (KE).•The SST-wind coupling has a negligible impact on KE and on the current feedback (CFB) strength over the study area.•The wind structure is influenced by CFB mainly through local mechanical processes, not thermodynamic or non-local ones.•The CFB reduces surface KE by 14% and extends down to 2000m, altering KE distribution throughout the water column.•Our results highlights the relevance of ABL1D coupling to capture wind-current interaction compared to bulk forcing methods.
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.
A one-dimensional Atmospheric Boundary Layer (ABL1D) is coupled with the NEMO ocean model and implemented over the Iberian–Biscay–Ireland (IBI) area at 1/36° resolution to investigate the ...retroactions between the surface currents and the atmosphere, namely the Current FeedBack (CFB) in this region of low mesoscale activity. The ABL1D-NEMO coupled model is forced by a large-scale atmospheric reanalysis (ERA-Interim) and integrated over the period 2016–2017. The mechanisms of eddy kinetic energy damping and ocean upper-layers re-energization are realistically simulated, meaning that the CFB is properly represented by the model. In particular, the dynamical coupling coefficients between the curls of surface stress/wind and current are in agreement with the literature. The effects of CFB on the kinetic energy (KE) are then investigated through a KE budget. We show that the KE decrease induced by the CFB is significant down to 1500 m. Near the surface (0–300 m), most of the KE decrease can be explained by a reduction of the surface wind work by 4 %. At depth (300–2000 m), the CFB induce a reduction of the pressure work (i.e: the PE to KE conversion) associated with a reduction of KE which is significant down to 1500 m. We show that this reduction of KE at depth can be explained by CFB-induced Ekman pumping above eddies that weakens the mesoscale activity and this over the whole water column.
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