scholarly journals iMarNet: an ocean biogeochemistry model inter-comparison project within a common physical ocean modelling framework

2014 ◽  
Vol 11 (7) ◽  
pp. 10537-10569 ◽  
Author(s):  
L. Kwiatkowski ◽  
A. Yool ◽  
J. I. Allen ◽  
T. R. Anderson ◽  
R. Barciela ◽  
...  
Keyword(s):  
General Circulation ◽  
High Efficiency ◽  
Circulation Model ◽  
Climate Dynamics ◽  
Model Complexity ◽  
Balance Model ◽  
Marine Biota ◽  
Earth System ◽  
Wide Range ◽  
Ocean Biogeochemistry

Abstract. Ocean biogeochemistry (OBGC) models span a wide range of complexities from highly simplified, nutrient-restoring schemes, through nutrient-phytoplankton-zooplankton-detritus (NPZD) models that crudely represent the marine biota, through to models that represent a broader trophic structure by grouping organisms as plankton functional types (PFT) based on their biogeochemical role (Dynamic Green Ocean Models; DGOM) and ecosystem models which group organisms by ecological function and trait. OBGC models are now integral components of Earth System Models (ESMs), but they compete for computing resources with higher resolution dynamical setups and with other components such as atmospheric chemistry and terrestrial vegetation schemes. As such, the choice of OBGC in ESMs needs to balance model complexity and realism alongside relative computing cost. Here, we present an inter-comparison of six OBGC models that were candidates for implementation within the next UK Earth System Model (UKESM1). The models cover a large range of biological complexity (from 7 to 57 tracers) but all include representations of at least the nitrogen, carbon, alkalinity and oxygen cycles. Each OBGC model was coupled to the Nucleus for the European Modelling of the Ocean (NEMO) ocean general circulation model (GCM), and results from physically identical hindcast simulations were compared. Model skill was evaluated for biogeochemical metrics of global-scale bulk properties using conventional statistical techniques. The computing cost of each model was also measured in standardised tests run at two resource levels. No model is shown to consistently outperform or underperform all other models across all metrics. Nonetheless, the simpler models that are easier to tune are broadly closer to observations across a number of fields, and thus offer a high-efficiency option for ESMs that prioritise high resolution climate dynamics. However, simpler models provide limited insight into more complex marine biogeochemical processes and ecosystem pathways, and a parallel approach of low resolution climate dynamics and high complexity biogeochemistry is desirable in order to provide additional insights into biogeochemistry–climate interactions.

scholarly journals iMarNet: an ocean biogeochemistry model intercomparison project within a common physical ocean modelling framework

2014 ◽  
Vol 11 (24) ◽  
pp. 7291-7304 ◽  
Author(s):  
L. Kwiatkowski ◽  
A. Yool ◽  
J. I. Allen ◽  
T. R. Anderson ◽  
R. Barciela ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
General Circulation ◽  
High Efficiency ◽  
Circulation Model ◽  
Climate Dynamics ◽  
Model Complexity ◽  
Balance Model ◽  
Marine Biota ◽  
Earth System ◽  
Ocean Biogeochemistry

Abstract. Ocean biogeochemistry (OBGC) models span a wide variety of complexities, including highly simplified nutrient-restoring schemes, nutrient–phytoplankton–zooplankton–detritus (NPZD) models that crudely represent the marine biota, models that represent a broader trophic structure by grouping organisms as plankton functional types (PFTs) based on their biogeochemical role (dynamic green ocean models) and ecosystem models that group organisms by ecological function and trait. OBGC models are now integral components of Earth system models (ESMs), but they compete for computing resources with higher resolution dynamical setups and with other components such as atmospheric chemistry and terrestrial vegetation schemes. As such, the choice of OBGC in ESMs needs to balance model complexity and realism alongside relative computing cost. Here we present an intercomparison of six OBGC models that were candidates for implementation within the next UK Earth system model (UKESM1). The models cover a large range of biological complexity (from 7 to 57 tracers) but all include representations of at least the nitrogen, carbon, alkalinity and oxygen cycles. Each OBGC model was coupled to the ocean general circulation model Nucleus for European Modelling of the Ocean (NEMO) and results from physically identical hindcast simulations were compared. Model skill was evaluated for biogeochemical metrics of global-scale bulk properties using conventional statistical techniques. The computing cost of each model was also measured in standardised tests run at two resource levels. No model is shown to consistently outperform all other models across all metrics. Nonetheless, the simpler models are broadly closer to observations across a number of fields and thus offer a high-efficiency option for ESMs that prioritise high-resolution climate dynamics. However, simpler models provide limited insight into more complex marine biogeochemical processes and ecosystem pathways, and a parallel approach of low-resolution climate dynamics and high-complexity biogeochemistry is desirable in order to provide additional insights into biogeochemistry–climate interactions.

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

2017 ◽  
Vol 10 (4) ◽  
pp. 1423-1445 ◽  
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.

scholarly journals PLASIM–GENIE v1.0: a new intermediate complexity AOGCM

2016 ◽  
Vol 9 (9) ◽  
pp. 3347-3361 ◽  
Author(s):  
Philip B. Holden ◽  
Neil R. Edwards ◽  
Klaus Fraedrich ◽  
Edilbert Kirk ◽  
Frank Lunkeit ◽  
...  
Keyword(s):  
General Circulation Model ◽  
Ocean Circulation ◽  
General Circulation ◽  
Circulation Model ◽  
Aridity Index ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
Intermediate Complexity ◽  
Wide Range

Abstract. We describe the development, tuning and climate of Planet Simulator (PLASIM)–Grid-ENabled Integrated Earth system model (GENIE), a new intermediate complexity Atmosphere–Ocean General Circulation Model (AOGCM), built by coupling the Planet Simulator to the ocean, sea-ice and land-surface components of the GENIE Earth system model. PLASIM–GENIE supersedes GENIE-2, a coupling of GENIE to the Reading Intermediate General Circulation Model (IGCM). The primitive-equation atmosphere includes chaotic, three-dimensional (3-D) motion and interactive radiation and clouds, and dominates the computational load compared to the relatively simpler frictional-geostrophic ocean, which neglects momentum advection. The model is most appropriate for long-timescale or large ensemble studies where numerical efficiency is prioritised, but lack of data necessitates an internally consistent, coupled calculation of both oceanic and atmospheric fields. A 1000-year simulation with PLASIM–GENIE requires approximately 2 weeks on a single node of a 2.1 GHz AMD 6172 CPU. We demonstrate the tractability of PLASIM–GENIE ensembles by deriving a subjective tuning of the model with a 50-member ensemble of 1000-year simulations. The simulated climate is presented considering (i) global fields of seasonal surface air temperature, precipitation, wind, solar and thermal radiation, with comparisons to reanalysis data; (ii) vegetation carbon, soil moisture and aridity index; and (iii) sea surface temperature, salinity and ocean circulation. Considering its resolution, PLASIM–GENIE reproduces the main features of the climate system well and demonstrates usefulness for a wide range of applications.

scholarly journals On the effect of orbital forcing on mid-Pliocene climate, vegetation and ice sheets

2013 ◽  
Vol 9 (2) ◽  
pp. 1703-1734 ◽  
Author(s):  
M. Willeit ◽  
A. Ganopolski ◽  
G. Feulner
Keyword(s):  
General Circulation ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Circulation Model ◽  
Warm Period ◽  
Vegetation Distribution ◽  
Orbital Forcing ◽  
Earth System ◽  
Wide Range ◽  
The Impact

Abstract. We present results from modeling of the mid-Pliocene warm period (3.3–3 million years ago) using the Earth system model of intermediate complexity CLIMBER-2 analyzing the effect of changes in boundary conditions as well as of orbital forcing on climate. Firstly we performed equilibrium experiments following PlioMIP (Pliocene Model Intercomparison Project) protocol with a CO2 concentration of 405 ppm, reconstructed mid-Pliocene orography and vegetation and a present day orbital configuration. Simulated global Pliocene warming is about 2.5 °C, fully consistent with results of atmosphere-ocean general circulation model simulations performed for the same modeling setup. A factor separation analysis attributes 1.5 °C warming to CO2, 0.3 °C to orography, 0.2 °C to ice sheets and 0.4 °C to vegetation. Transient simulations for the entire mid-Pliocene warm period with time-dependent orbital forcing as well as interactive ice sheets and vegetation give a global warming varying within the range 1.9–2.8 °C. Ice sheet and vegetation feedbacks in synergy act as amplifiers of the orbital forcing transforming seasonal insolation variations into an annual mean temperature signal. The effect of orbital forcing is more significant at high latitudes, especially during summer, when the warming over land varies in the wide range from 0–10 °C. The modeled ice sheet extent and vegetation distribution also show significant temporal variations. Modeled and reconstructed data for Northern Hemisphere sea surface temperatures and vegetation distribution show the best agreement if the reconstructions are assumed to be representative for the "warmest" periods during the orbital cycles. This suggests that low-resolution Pliocene paleoclimate reconstructions can reflect not only the impact of increased CO2 concentrations and topography changes but also the effect of orbital forcing. Therefore, the climate (Earth system) sensitivity estimates from Pliocene reconstructions which do not account for the effect of orbital forcing can be biased toward high values.

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

2016 ◽  
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.

scholarly journals Do Downscaled General Circulation Models Reliably Simulate Historical Climatic Conditions?

2018 ◽  
Vol 22 (10) ◽  
pp. 1-22 ◽  
Author(s):  
Andrew R. Bock ◽  
Lauren E. Hay ◽  
Gregory J. McCabe ◽  
Steven L. Markstrom ◽  
R. Dwight Atkinson
Keyword(s):  
General Circulation ◽  
Statistical Tests ◽  
Circulation Model ◽  
General Circulation Models ◽  
Climatic Conditions ◽  
Low Flow ◽  
Balance Model ◽  
Monthly Precipitation ◽  
Significance Level ◽  
Ks Test

Abstract The accuracy of statistically downscaled (SD) general circulation model (GCM) simulations of monthly surface climate for historical conditions (1950–2005) was assessed for the conterminous United States (CONUS). The SD monthly precipitation (PPT) and temperature (TAVE) from 95 GCMs from phases 3 and 5 of the Coupled Model Intercomparison Project (CMIP3 and CMIP5) were used as inputs to a monthly water balance model (MWBM). Distributions of MWBM input (PPT and TAVE) and output [runoff (RUN)] variables derived from gridded station data (GSD) and historical SD climate were compared using the Kolmogorov–Smirnov (KS) test For all three variables considered, the KS test results showed that variables simulated using CMIP5 generally are more reliable than those derived from CMIP3, likely due to improvements in PPT simulations. At most locations across the CONUS, the largest differences between GSD and SD PPT and RUN occurred in the lowest part of the distributions (i.e., low-flow RUN and low-magnitude PPT). Results indicate that for the majority of the CONUS, there are downscaled GCMs that can reliably simulate historical climatic conditions. But, in some geographic locations, none of the SD GCMs replicated historical conditions for two of the three variables (PPT and RUN) based on the KS test, with a significance level of 0.05. In these locations, improved GCM simulations of PPT are needed to more reliably estimate components of the hydrologic cycle. Simple metrics and statistical tests, such as those described here, can provide an initial set of criteria to help simplify GCM selection.

scholarly journals Atmospheric dynamics on terrestrial planets with eccentric orbits

2020 ◽  
Author(s):  
Ilai Guendelman ◽  
Yohai Kaspi
Keyword(s):  
General Circulation ◽  
Circulation Model ◽  
Balance Model ◽  
Maximum Temperature ◽  
Climate Response ◽  
Eccentric Orbits ◽  
Orbital Configuration ◽  
Main Engine ◽  
Atmospheric Moisture Content ◽  
Parent Star

<p>The insolation a planet receives from its parent star is the main engine of the climate and depends on the planet's orbital configuration. Planets with non-zero obliquity and eccentricity experience seasonal insolation variations. As a result, the climate exhibits a seasonal cycle, with its strength depending on the orbital configuration and atmospheric characteristics. In this study, using an idealized general circulation model, we examine the climate response to changes in eccentricity for both zero and non-zero obliquity planets. In the zero obliquity case, a comparison between the seasonal response to changes in eccentricity and perpetual changes in the solar constant shows that the seasonal response strongly depends on the orbital period and radiative timescale. More specifically, using a simple energy balance model, we show the importance of the latitudinal structure of the radiative timescale in the climate response. We also show that the response strongly depends on the atmospheric moisture content. The combination of an eccentric orbit with non-zero obliquity is complex, as the insolation also depends on the perihelion position. Although the detailed response of the climate to variations in eccentricity, obliquity, and perihelion is involved, the circulation is constrained mainly by the thermal Rossby number and the maximum temperature latitude. Finally, we discuss the importance of different planetary parameters that affect the climate response to orbital configuration variations.</p>

Response of tropical rainfall to reduced evapotranspiration depends on continental extent

2021 ◽  
pp. 1-50
Author(s):  
Marianne Pietschnig ◽  
Abigail L. S. Swann ◽  
F. Hugo Lambert ◽  
Geoffrey K. Vallis
Keyword(s):  
Stomatal Conductance ◽  
General Circulation ◽  
Amazon Basin ◽  
Circulation Model ◽  
Complex Model ◽  
Earth System ◽  
Area Index ◽  
Tropical Rainfall ◽  
System Models ◽  
Earth System Models

AbstractFuture projections of precipitation change over tropical land are often enhanced by vegetation responses to CO2 forcing in Earth System Models. Projected decreases in rainfall over the Amazon basin and increases over the Maritime Continent are both stronger when plant physiological changes are modelled than if these changes are neglected, but the reasons for this amplification remain unclear. The responses of vegetation to increasing CO2 levels are complex and uncertain, including possible decreases in stomatal conductance and increases in leaf area index due to CO2-fertilisation. Our results from an idealised Atmospheric General Circulation Model show that the amplification of rainfall changes occurs even when we use a simplified vegetation parameterisation based solely on CO2-driven decreases in stomatal conductance, indicating that this mechanism plays a key role in complex model projections. Based on simulations with rectangular continentswe find that reducing terrestrial evaporation to zero with increasing CO2 notably leads to enhanced rainfall over a narrow island. Strong heating and ascent over the island trigger moisture advection from the surrounding ocean. In contrast, over larger continents rainfall depends on continental evaporation. Simulations with two rectangular continents representing South America and Africa reveal that the stronger decrease in rainfall over the Amazon basin seen in Earth System Models is due to a combination of local and remote effects, which are fundamentally connected to South America’s size and its location with respect to Africa. The response of tropical rainfall to changes in evapotranspiration is thus connected to size and configuration of the continents.

scholarly journals On the Near-Inertial Resonance of the Atlantic Meridional Overturning Circulation

2013 ◽  
Vol 43 (12) ◽  
pp. 2661-2672 ◽  
Author(s):  
Florian Sévellec ◽  
Joël J.-M. Hirschi ◽  
Adam T. Blaker
Keyword(s):  
General Circulation ◽  
Numerical Models ◽  
Circulation Model ◽  
Atlantic Meridional Overturning Circulation ◽  
Meridional Overturning Circulation ◽  
Resonance Phenomenon ◽  
Dimensionless Number ◽  
Overturning Circulation ◽  
Wide Range ◽  
Meridional Overturning

Abstract The Atlantic meridional overturning circulation (AMOC) is a crucial component of the global climate system. It is responsible for around a quarter of the global northward heat transport and contributes to the mild European climate. Observations and numerical models suggest a wide range of AMOC variability. Recent results from an ocean general circulation model (OGCM) in a high-resolution configuration (¼°) suggest the existence of superinertial variability of the AMOC. In this study, the validity of this result in a theoretical framework is tested. At a low Rossby number and in the presence of Rayleigh friction, it is demonstrated that, unlike a typical forced damped oscillator (which shows subinertial resonance), the AMOC undergoes both super- and subinertial resonances (except at low latitudes and for high friction). A dimensionless number Sr, measuring the ratio of ageo- to geostrophic forcing (i.e., the zonal versus meridional pressure gradients), indicates which of these resonances dominates. If Sr ≪ 1, the AMOC variability is mainly driven by geostrophic forcing and shows subinertial resonance. Alternatively and consistent with the recently published ¼° OGCM experiments, if Sr ≫ 1, the AMOC variability is mainly driven by the ageostrophic forcing and shows superinertial resonance. In both regimes, a forcing of ±1 K induces an AMOC variability of ±10 Sv (1 Sv ≡ 106 m3 s−1) through these near-inertial resonance phenomena. It is also shown that, as expected from numerical simulations, the spatial structure of the near-inertial AMOC variability corresponds to equatorward-propagating waves equivalent to baroclinic Poincaré waves. The long-time average of this resonance phenomenon, raising and depressing the pycnocline, could contribute to the mixing of the ocean stratification.

scholarly journals The Stability of Incremental Analysis Update

2018 ◽  
Vol 146 (10) ◽  
pp. 3259-3275 ◽  
Author(s):  
Lawrence L. Takacs ◽  
Max J. Suárez ◽  
Ricardo Todling
Keyword(s):  
Digital Filter ◽  
General Circulation ◽  
Circulation Model ◽  
Stability Diagram ◽  
Recent Attempt ◽  
Complex Frequency ◽  
Incremental Analysis ◽  
Wide Range ◽  
The Stability ◽  
Background Fields

Abstract A recent attempt to downscale the 50-km MERRA-2 analyses to 7 km revealed an instability associated with the incremental analysis update (IAU) procedure that has thus far gone unnoticed. A theoretical study based on a simple damped harmonic oscillator with complex frequency provides the framework to diagnose the problem and suggests means to avoid it. Three possible approaches to avoid the instability are to (i) choose an “ideal” ratio of the lengths of the predictor and corrector steps of IAU based on a theoretical stability diagram, (ii) time average the background fields used to construct the IAU tendencies with given frequency, or (iii) apply a digital filter modulation to the IAU tendencies. All these are shown to control the instability for a wide range of resolutions when doing up- or downscaling, experiments with the NASA GMAO atmospheric general circulation model. Furthermore, it is found that combining IAU with the ensemble recentering step typical of hybrid ensemble–variational approaches also results in an instability based on the same mechanisms in the members of the ensemble. An example of such occurrence arises in an experiment performed with the GMAO 12.8-km hybrid 4D-EnVar system. Modulation of the ensemble IAU tendencies with a digital filter is shown to avoid the instability. In addition, the stability of certain 4D incremental analysis update (4DIAU) implementations is analyzed and a suggestion is made to improve its results, though a complete study of this subject is postponed to a follow-up work.

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