scholarly journals Towards multiscale modeling of ocean surface turbulent mixing using coupled MPAS-Ocean v6.3 and PALM v5.0

2021 ◽  
Vol 14 (4) ◽  
pp. 2011-2028
Author(s):  
Qing Li ◽  
Luke Van Roekel
Keyword(s):  
Multiscale Modeling ◽  
Turbulent Mixing ◽  
General Circulation ◽  
Ocean Surface ◽  
Global Ocean ◽  
Small Scale ◽  
Processing Unit ◽  
Flexible Coupling ◽  
Modeling Approach ◽  
Large Eddy

Abstract. A multiscale modeling approach for studying the ocean surface turbulent mixing is explored by coupling an ocean general circulation model (GCM) MPAS-Ocean with the Parallelized Large Eddy Simulation Model (PALM). The coupling approach is similar to the superparameterization approach that has been used to represent the effects of deep convection in atmospheric GCMs. However, the focus of this multiscale modeling approach is on the small-scale turbulent mixing and their interactions with the larger-scale processes in the ocean, so that a more flexible coupling strategy is used. To reduce the computational cost, a customized version of PALM is ported on the general-purpose graphics processing unit (GPU) with OpenACC, achieving 10–16 times overall speedup as compared to running on a single CPU. Even with the GPU-acceleration technique, a superparameterization-like approach to represent the ocean surface turbulent mixing in GCMs using embedded high fidelity and three-dimensional large eddy simulations (LESs) over the global ocean is still computationally intensive and infeasible for long simulations. However, running PALM regionally on selected MPAS-Ocean grid cells is shown to be a promising approach moving forward. The flexible coupling between MPAS-Ocean and PALM allows further exploration of the interactions between the ocean surface turbulent mixing and larger-scale processes, as well as future development and improvement of ocean surface turbulent mixing parameterizations for GCMs.

scholarly journals Towards Multiscale Modeling of Ocean Surface Turbulent Mixing Using Coupled MPAS-Ocean v6.3 and PALM v5.0

2020 ◽  
Author(s):  
Qing Li ◽  
Luke Van Roekel
Keyword(s):  
Large Eddy Simulation ◽  
Multiscale Modeling ◽  
Turbulent Mixing ◽  
Three Dimensional ◽  
Ocean Surface ◽  
Global Ocean ◽  
High Fidelity ◽  
Processing Unit ◽  
Eddy Simulation ◽  
Large Eddy

Abstract. A multiscale modeling approach for studying the ocean surface turbulent mixing is explored by coupling an ocean general circulation model (GCM) MPAS-Ocean with the PArallel Large eddy simulation Model (PALM). The coupling approach is similar to the superparameterization approach that has been used mostly to represent the effects of deep convection in atmospheric GCMs. However, since the emphasis here is on the small-scale turbulent mixing processes and their interactions with the larger-scale processes, a high-fidelity, three-dimensional large eddy simulation (LES) model is used, in contrary to a simplified process-resolving model with reduced physics or reduced dimension commonly used in the superparameterization literature. To reduce the computational cost, a customized version of PALM is ported on the general-purpose graphics processing unit (GPU) with OpenACC, achieving 10–16 times overall speedup as compared to running on a single CPU. Even with the GPU-acceleration technique, superparameterization of the ocean surface turbulent mixing using high-fidelity and three-dimensional LES over the global ocean in GCMs is still computationally intensive and infeasible for long simulations. However, running PALM regionally on selected MPAS-Ocean grid cells is shown to be a promising approach moving forward. The flexible coupling between MPAS-Ocean and PALM outlined here allows further exploration of the interactions between ocean surface turbulent mixing and larger-scale processes, and development of better ocean surface turbulent mixing parameterizations in GCMs.

LESbrary: A library of large eddy simulation data for the calibration and uncertainty quantification of ocean surface boundary layer turbulence parameterizations

2021 ◽  
Author(s):  
Gregory Wagner ◽  
Andre Souza ◽  
Adeline Hillier ◽  
Ali Ramadhan ◽  
Raffaele Ferrari
Keyword(s):  
Boundary Layer ◽  
Turbulent Mixing ◽  
Large Scale ◽  
Ocean Surface ◽  
Limited Area ◽  
Surface Boundary ◽  
Model Errors ◽  
Surface Boundary Layer ◽  
Large Eddy ◽  
Free Parameters

<p>Parameterizations of turbulent mixing in the ocean surface boundary layer (OSBL) are key Earth System Model (ESM) components that modulate the communication of heat and carbon between the atmosphere and ocean interior. OSBL turbulence parameterizations are formulated in terms of unknown free parameters estimated from observational or synthetic data. In this work we describe the development and use of a synthetic dataset called the “LESbrary” generated by a large number of idealized, high-fidelity, limited-area large eddy simulations (LES) of OSBL turbulent mixing. We describe how the LESbrary design leverages a detailed understanding of OSBL conditions derived from observations and large scale models to span the range of realistically diverse physical scenarios. The result is a diverse library of well-characterized “synthetic observations” that can be readily assimilated for the calibration of realistic OSBL parameterizations in isolation from other ESM model components. We apply LESbrary data to calibrate free parameters, develop prior estimates of parameter uncertainty, and evaluate model errors in two OSBL parameterizations for use in predictive ESMs.</p>

scholarly journals Inhomogeneous Mixing in Lagrangian Cloud Models: Effects on the Production of Precipitation Embryos

2018 ◽  
Vol 76 (1) ◽  
pp. 113-133 ◽  
Author(s):  
Fabian Hoffmann ◽  
Takanobu Yamaguchi ◽  
Graham Feingold
Keyword(s):  
Turbulent Mixing ◽  
Cloud Model ◽  
Small Scale ◽  
New Approach ◽  
Air Masses ◽  
Lagrangian Particles ◽  
Cloud Models ◽  
Large Eddy ◽  
Salutary Effect ◽  
Linear Eddy Model

Abstract Although small-scale turbulent mixing at cloud edge has substantial effects on the microphysics of clouds, most models do not represent these processes explicitly, or parameterize them rather crudely. This study presents a first use of the linear eddy model (LEM) to represent unresolved turbulent mixing at the subgrid scale (SGS) of large-eddy simulations (LESs) with a coupled Lagrangian cloud model (LCM). The method utilizes Lagrangian particles to provide the trajectory of air masses within LES grid boxes, while the LEM is used to redistribute these air masses among the Lagrangian particles based on the local features of turbulence, allowing for the appropriate representation of inhomogeneous to homogeneous SGS mixing. The new approach has the salutary effect of mitigating spurious supersaturations. At low turbulence intensities, as found in the early stages of an idealized bubble cloud simulation, cloud-edge SGS mixing tends to be inhomogeneous and the new approach is shown to be essential for the production of raindrop embryos. At higher turbulence intensities, as found in a field of shallow cumulus, SGS mixing tends to be more homogeneous and the new approach does not significantly alter the results, indicating that a grid spacing of 20 m may be sufficient to resolve all relevant scales of inhomogeneous mixing. In both cases, droplet in-cloud residence times are important for the production of precipitation embryos in the absence of small-scale inhomogeneous mixing, either naturally due to strong turbulence or artificially as a result of coarse resolution or by not using the LEM as an SGS model.

scholarly journals Mean Dynamic Topography of the Ocean Derived from Satellite and Drifting Buoy Data Using Three Different Techniques*

2009 ◽  
Vol 26 (9) ◽  
pp. 1910-1919 ◽  
Author(s):  
Nikolai Maximenko ◽  
Peter Niiler ◽  
Luca Centurioni ◽  
Marie-Helene Rio ◽  
Oleg Melnichenko ◽  
...  
Keyword(s):  
Ocean Surface ◽  
Horizontal Resolution ◽  
Global Ocean ◽  
Momentum Balance ◽  
Small Scale ◽  
Western Boundary ◽  
Dynamic Topography ◽  
Geoid Model ◽  
Near Surface ◽  
Mean Dynamic Topography

Abstract Presented here are three mean dynamic topography maps derived with different methodologies. The first method combines sea level observed by the high-accuracy satellite radar altimetry with the geoid model of the Gravity Recovery and Climate Experiment (GRACE), which has recently measured the earth’s gravity with unprecedented spatial resolution and accuracy. The second one synthesizes near-surface velocities from a network of ocean drifters, hydrographic profiles, and ocean winds sorted according to the horizontal scales. In the third method, these global datasets are used in the context of the ocean surface momentum balance. The second and third methods are used to improve accuracy of the dynamic topography on fine space scales poorly resolved in the first method. When they are used to compute a multiyear time-mean global ocean surface circulation on a 0.5° horizontal resolution, both contain very similar, new small-scale midocean current patterns. In particular, extensions of western boundary currents appear narrow and strong despite temporal variability and exhibit persistent meanders and multiple branching. Also, the locations of the velocity concentrations in the Antarctic Circumpolar Current become well defined. Ageostrophic velocities reveal convergent zones in each subtropical basin. These maps present a new context in which to view the continued ocean monitoring with in situ instruments and satellites.

scholarly journals The GPU version of LASG/IAP Climate System Ocean Model version 3 (LICOM3) under the heterogeneous-compute interface for portability (HIP) framework and its large-scale application

2021 ◽  
Vol 14 (5) ◽  
pp. 2781-2799
Author(s):  
Pengfei Wang ◽  
Jinrong Jiang ◽  
Pengfei Lin ◽  
Mengrong Ding ◽  
Junlin Wei ◽  
...  
Keyword(s):  
General Circulation ◽  
Large Scale ◽  
Vertical Direction ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Ocean Model ◽  
Climate System ◽  
Global Ocean ◽  
Processing Unit ◽  
Model Version

Abstract. A high-resolution (1/20∘) global ocean general circulation model with graphics processing unit (GPU) code implementations is developed based on the LASG/IAP Climate System Ocean Model version 3 (LICOM3) under a heterogeneous-compute interface for portability (HIP) framework. The dynamic core and physics package of LICOM3 are both ported to the GPU, and three-dimensional parallelization (also partitioned in the vertical direction) is applied. The HIP version of LICOM3 (LICOM3-HIP) is 42 times faster than the same number of CPU cores when 384 AMD GPUs and CPU cores are used. LICOM3-HIP has excellent scalability; it can still obtain a speedup of more than 4 on 9216 GPUs compared to 384 GPUs. In this phase, we successfully performed a test of 1/20∘ LICOM3-HIP using 6550 nodes and 26 200 GPUs, and on a large scale, the model's speed was increased to approximately 2.72 simulated years per day (SYPD). By putting almost all the computation processes inside GPUs, the time cost of data transfer between CPUs and GPUs was reduced, resulting in high performance. Simultaneously, a 14-year spin-up integration following phase 2 of the Ocean Model Intercomparison Project (OMIP-2) protocol of surface forcing was performed, and preliminary results were evaluated. We found that the model results had little difference from the CPU version. Further comparison with observations and lower-resolution LICOM3 results suggests that the 1/20∘ LICOM3-HIP can reproduce the observations and produce many smaller-scale activities, such as submesoscale eddies and frontal-scale structures.

scholarly journals Ice-shelf ocean boundary layer dynamics from large-eddy simulations

2021 ◽  
Author(s):  
Carolyn Branecky Begeman ◽  
Xylar Asay-Davis ◽  
Luke Van Roekel
Keyword(s):  
Boundary Layer ◽  
Ocean Circulation ◽  
Large Eddy Simulations ◽  
Global Ocean ◽  
Small Scale ◽  
Parameter Study ◽  
Ice Shelf ◽  
Ice Shelves ◽  
Large Eddy ◽  
Ocean Boundary

Abstract. Small scale, turbulent flow below ice shelves is regionally isolated and difficult to measure and simulate. Yet these small scale processes, which regulate heat transfer between the ocean and ice shelves, can affect sea-level rise by altering the ability of Antarctic ice shelves to “buttress” ice flux to the ocean. In this study, we improve our understanding of turbulence below ice shelves by means of large-eddy simulations at sub-meter resolution, capturing boundary layer mixing at scales intermediate between laboratory experiments or direct numerical simulations and regional or global ocean circulation models. Our simulations feature the development of an ice-shelf ocean boundary layer through dynamic ice melting in a regime with low thermal driving, low ice-shelf basal slope, and strong shear driven by the geostrophic flow. We present a preliminary assessment of existing ice-shelf basal melt parameterizations adopted in single component or coupled ice-sheet and ocean models on the basis of a small parameter study. While the parameterized linear relationship between ice-shelf melt rate and far-field ocean temperature appears to be robust, we point out a little-considered relationship between ice-shelf basal slope and melting worthy of further study.

scholarly journals Decadal-Mean Impact of Including Ocean Surface Currents in Bulk Formulas on Surface Air–Sea Fluxes and Ocean General Circulation

2017 ◽  
Vol 30 (23) ◽  
pp. 9511-9525 ◽  
Author(s):  
Yang Wu ◽  
Xiaoming Zhai ◽  
Zhaomin Wang
Keyword(s):  
Wind Stress ◽  
General Circulation ◽  
Surface Wind ◽  
Ocean Surface ◽  
Meridional Overturning Circulation ◽  
Global Ocean ◽  
Turbulent Heat ◽  
Surface Currents ◽  
Ocean Surface Currents ◽  
Ocean General Circulation

The decadal-mean impact of including ocean surface currents in the bulk formulas on surface air–sea fluxes and the ocean general circulation is investigated for the first time using a global eddy-permitting coupled ocean–sea ice model. Although including ocean surface currents in air–sea flux calculations only weakens the surface wind stress by a few percent, it significantly reduces wind power input to both geostrophic and ageostrophic motions, and damps the eddy and mean kinetic energy throughout the water column. Furthermore, the strength of the horizontal gyre circulations and the Atlantic meridional overturning circulation are found to decrease considerably (by 10%–15% and ~13%, respectively). As a result of the weakened ocean general circulation, the maximum northward global ocean heat transport decreases by about 0.2 PW, resulting in a lower sea surface temperature and reduced surface heat loss in the northern North Atlantic. Additional sensitivity model experiments further demonstrate that it is including ocean surface currents in the wind stress calculation that dominates this decadal impact, with including ocean surface currents in the turbulent heat flux calculations making only a minor contribution. These results highlight the importance of properly accounting for ocean surface currents in surface air–sea fluxes in modeling the ocean circulation and climate.

scholarly journals Intrinsic Variability of Sea Level from Global Ocean Simulations: Spatiotemporal Scales

2015 ◽  
Vol 28 (10) ◽  
pp. 4279-4292 ◽  
Author(s):  
Guillaume Sérazin ◽  
Thierry Penduff ◽  
Sandy Grégorio ◽  
Bernard Barnier ◽  
Jean-Marc Molines ◽  
...  
Keyword(s):  
Sea Level ◽  
Time Scales ◽  
General Circulation ◽  
Spatial Scales ◽  
Full Range ◽  
Low Frequency ◽  
Global Ocean ◽  
Small Scale ◽  
Atmospheric Variability ◽  
Low Frequencies

Abstract In high-resolution ocean general circulation models (OGCMs), as in process-oriented models, a substantial amount of interannual to decadal variability is generated spontaneously by oceanic nonlinearities: that is, without any variability in the atmospheric forcing at these time scales. The authors investigate the temporal and spatial scales at which this intrinsic oceanic variability has the strongest imprints on sea level anomalies (SLAs) using a ° global OGCM, by comparing a “hindcast” driven by the full range of atmospheric time scales with its counterpart forced by a repeated climatological atmospheric seasonal cycle. Outputs from both simulations are compared within distinct frequency–wavenumber bins. The fully forced hindcast is shown to reproduce the observed distribution and magnitude of low-frequency SLA variability very accurately. The small-scale (L < 6°) SLA variance is, at all time scales, barely sensitive to atmospheric variability and is almost entirely of intrinsic origin. The high-frequency (mesoscale) part and the low-frequency part of this small-scale variability have almost identical geographical distributions, supporting the hypothesis of a nonlinear temporal inverse cascade spontaneously transferring kinetic energy from high to low frequencies. The large-scale (L > 12°) low-frequency variability is mostly related to the atmospheric variability over most of the global ocean, but it is shown to remain largely intrinsic in three eddy-active regions: the Gulf Stream, Kuroshio, and Antarctic Circumpolar Current (ACC). Compared to its ¼° predecessor, the authors’ ° OGCM is shown to yield a stronger intrinsic SLA variability, at both mesoscale and low frequencies.

scholarly journals Water isotope variations in the global ocean model MPI-OM

2012 ◽  
Vol 5 (3) ◽  
pp. 809-818 ◽  
Author(s):  
X. Xu ◽  
M. Werner ◽  
M. Butzin ◽  
G. Lohmann
Keyword(s):  
Surface Waters ◽  
General Circulation ◽  
Large Scale ◽  
Circulation Model ◽  
Deep Ocean ◽  
Ocean Surface ◽  
Ocean Model ◽  
Global Ocean ◽  
Stable Water Isotopes ◽  
Tropical Regions

Abstract. The stable water isotopes H218O and HDO are incorporated as passive tracers into the oceanic general circulation model MPI-OM, and a control simulation under present-day climate conditions is analyzed in detail. Both δ18O and δD distributions at the ocean surface and deep ocean are generally consistent with available observations on the large scale. The modelled δD-δ 18O relations in surface waters slightly deviates from the slope of the global meteoric water line in most basins, and a much steeper slope is detected in Arctic Oceans. The simulated deuterium excess of ocean surface waters shows small variations between 80° S and 55° N, and a strong decrease north of 55° N. The model is also able to capture the quasi-linear relationship between δ18O and salinity S, as well as δD and S, as seen in observational data. Both in the model results and observations, the surface δ−S relations show a steeper slope in extra-tropical regions than in tropical regions, which indicates relatively more addition of isotopically depleted water at high latitudes.

scholarly journals Efficiency of small scale carbon mitigation by patch iron fertilization

2010 ◽  
Vol 7 (11) ◽  
pp. 3593-3624 ◽  
Author(s):  
J. L. Sarmiento ◽  
R. D. Slater ◽  
J. Dunne ◽  
A. Gnanadesikan ◽  
M. R. Hiscock
Keyword(s):  
Southern Ocean ◽  
General Circulation ◽  
Ross Sea ◽  
Equatorial Pacific ◽  
Global Ocean ◽  
Small Scale ◽  
Co2 Uptake ◽  
The North ◽  
Biogeochemical Models ◽  
Iron Fertilization

Abstract. While nutrient depletion scenarios have long shown that the high-latitude High Nutrient Low Chlorophyll (HNLC) regions are the most effective for sequestering atmospheric carbon dioxide, recent simulations with prognostic biogeochemical models have suggested that only a fraction of the potential drawdown can be realized. We use a global ocean biogeochemical general circulation model developed at GFDL and Princeton to examine this and related issues. We fertilize two patches in the North and Equatorial Pacific, and two additional patches in the Southern Ocean HNLC region north of the biogeochemical divide and in the Ross Sea south of the biogeochemical divide. We evaluate the simulations using observations from both artificial and natural iron fertilization experiments at nearby locations. We obtain by far the greatest response to iron fertilization at the Ross Sea site, where sea ice prevents escape of sequestered CO2 during the wintertime, and the CO2 removed from the surface ocean by the biological pump is carried into the deep ocean by the circulation. As a consequence, CO2 remains sequestered on century time-scales and the efficiency of fertilization remains almost constant no matter how frequently iron is applied as long as it is confined to the growing season. The second most efficient site is in the Southern Ocean. The North Pacific site has lower initial nutrients and thus a lower efficiency. Fertilization of the Equatorial Pacific leads to an expansion of the suboxic zone and a striking increase in denitrification that causes a sharp reduction in overall surface biological export production and CO2 uptake. The impacts on the oxygen distribution and surface biological export are less prominent at other sites, but nevertheless still a source of concern. The century time scale retention of iron in this model greatly increases the long-term biological response to iron addition as compared with simulations in which the added iron is rapidly scavenged from the ocean.

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