Using Green’s Functions to initialize and adjust a global, eddying ocean biogeochemistry general circulation model

Abstract Green's functions provide a simple yet effective method to test and to calibrate general circulation model (GCM) parameterizations, to study and to quantify model and data errors, to correct model biases and trends, and to blend estimates from different solutions and data products. The method is applied to an ocean GCM, resulting in substantial improvements of the solution relative to observations when compared to prior estimates: overall model bias and drift are reduced and there is a 10%–30% increase in explained variance. Within the context of this optimization, the following new estimates for commonly used ocean GCM parameters are obtained. Background vertical diffusivity is (15.1 ± 0.1) × 10−6 m2 s−2. Background vertical viscosity is (18 ± 3) × 10−6 m2 s−2. The critical bulk Richardson number, which sets boundary layer depth, is Ric = 0.354 ± 0.004. The threshold gradient Richardson number for shear instability vertical mixing is Ri0 = 0.699 ± 0.008. The estimated isopycnal diffusivity coefficient ranges from 550 to 1350 m2 s−2, with the largest values occurring at depth in regions of increased mesoscale eddy activity. Surprisingly, the estimated isopycnal diffusivity exhibits a 5%–35% decrease near the surface. Improved estimates of initial and boundary conditions are also obtained. The above estimates are the backbone of a quasi-operational, global-ocean circulation analysis system.

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Development of BFMCOUPLER (v1.0), the coupling scheme that links the MITgcm and BFM models for ocean biogeochemistry simulations

Geoscientific Model Development ◽

10.5194/gmd-10-1423-2017 ◽

2017 ◽

Vol 10 (4) ◽

pp. 1423-1445 ◽

Cited By ~ 12

Author(s):

Gianpiero Cossarini ◽

Stefano Querin ◽

Cosimo Solidoro ◽

Gianmaria Sannino ◽

Paolo Lazzari ◽

...

Keyword(s):

Mediterranean Sea ◽

General Circulation Model ◽

General Circulation ◽

Circulation Model ◽

Biogeochemical Model ◽

Coupling Scheme ◽

Integration Schemes ◽

Wide Range ◽

Ocean Biogeochemistry ◽

The Mediterranean

Abstract. In this paper, we present a coupling scheme between the Massachusetts Institute of Technology general circulation model (MITgcm) and the Biogeochemical Flux Model (BFM). The MITgcm and BFM are widely used models for geophysical fluid dynamics and for ocean biogeochemistry, respectively, and they benefit from the support of active developers and user communities. The MITgcm is a state-of-the-art general circulation model for simulating the ocean and the atmosphere. This model is fully 3-D (including the non-hydrostatic term of momentum equations) and is characterized by a finite-volume discretization and a number of additional features enabling simulations from global (O(107) m) to local scales (O(100) m). The BFM is a biogeochemical model based on plankton functional type formulations, and it simulates the cycling of a number of constituents and nutrients within marine ecosystems. The online coupling presented in this paper is based on an open-source code, and it is characterized by a modular structure. Modularity preserves the potentials of the two models, allowing for a sustainable programming effort to handle future evolutions in the two codes. We also tested specific model options and integration schemes to balance the numerical accuracy against the computational performance. The coupling scheme allows us to solve several processes that are not considered by each of the models alone, including light attenuation parameterizations along the water column, phytoplankton and detritus sinking, external inputs, and surface and bottom fluxes. Moreover, this new coupled hydrodynamic–biogeochemical model has been configured and tested against an idealized problem (a cyclonic gyre in a mid-latitude closed basin) and a realistic case study (central part of the Mediterranean Sea in 2006–2012). The numerical results consistently reproduce the interplay of hydrodynamics and biogeochemistry in both the idealized case and Mediterranean Sea experiments. The former reproduces correctly the alternation of surface bloom and deep chlorophyll maximum dynamics driven by the seasonal cycle of winter vertical mixing and summer stratification; the latter simulates the main basin-wide and mesoscale spatial features of the physical and biochemical variables in the Mediterranean, thus demonstrating the applicability of the new coupled model to a wide range of ocean biogeochemistry problems.

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Development of BFMCOUPLER (v1.0), the coupling scheme that links the MITgcm and BFM models for ocean biogeochemistry simulations

10.5194/gmd-2016-222 ◽

2016 ◽

Cited By ~ 1

Author(s):

Gianpiero Cossarini ◽

Stefano Querin ◽

Cosimo Solidoro ◽

Gianmaria Sannino ◽

Paolo Lazzari ◽

...

Keyword(s):

General Circulation Model ◽

General Circulation ◽

Light Attenuation ◽

Circulation Model ◽

Biogeochemical Model ◽

Coupling Scheme ◽

Computational Performance ◽

Wide Range ◽

Ocean Biogeochemistry ◽

The Mediterranean

Abstract. In this paper, we present a coupling scheme between the Massachusetts Institute of Technology general circulation model (MITgcm) and the Biogeochemical Flux Model (BFM). The MITgcm and BFM are widely used models for geophysical fluid dynamics and for ocean biogeochemistry, respectively, and they benefit from the support of active developers and user communities. The MITgcm is a state-of-the-art general circulation model for simulating the ocean and the atmosphere. This model is fully three dimensional (including the non-hydrostatic term of momentum equations) and includes a finite-volume discretization and a number of additional features enabling simulations from global (O(107)m) to local scales (O(100)m). The BFM is a complex biogeochemical model that simulates the cycling of a number of constituents and nutrients within marine ecosystems. The coupler presented in this paper links the two models through an efficient scheme that manages communication and memory sharing between the models. We also test specific model options to balance the numerical accuracy against the computational performance. The coupling scheme allows us to solve several processes that are not considered by each of the models alone, including light attenuation parameterizations along the water column, phytoplankton and detritus sinking, external inputs, and surface and bottom fluxes. Moreover, this new coupled hydrodynamic-biogeochemical model has been configured and tested against an idealized problem (a cyclonic gyre in a mid-latitude closed basin) and a realistic case study (central part of the Mediterranean Sea in 2006–2012). The numerical results are consistent with the expected theoretical and observed behaviour of both the idealized system and the Mediterranean domain, thus demonstrating the applicability of the new coupled model to a wide range of ocean biogeochemistry problems.

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