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Geographical Distribution Of Diurnal And Semidiurnal Parametric Subharmonic Instability In A Global Ocean Circulation Model
Title
Geographical Distribution Of Diurnal And Semidiurnal Parametric Subharmonic Instability In A Global Ocean Circulation Model.
Creator
Ansong, Joseph K., Arbic, Brian K., Simmons, Harper L., Alford, Matthew H., Buijsman, Maarten C., Timko, Patrick G., Richman, James G., Shriver, Jay F., Wallcraft, Alan J.
Abstract/Description
The evidence for, baroclinic energetics of, and geographic distribution of parametric subharmonic instability (PSI) arising from both diurnal and semidiurnal tides in a global ocean general circulation model is investigated using 1/12.5 degrees and 1/25 degrees simulations that are forced by both atmospheric analysis fields and the astronomical tidal potential. The paper examines whether PSI occurs in the model, and whether it accounts for a significant fraction of the tidal baroclinic energy...
Show moreThe evidence for, baroclinic energetics of, and geographic distribution of parametric subharmonic instability (PSI) arising from both diurnal and semidiurnal tides in a global ocean general circulation model is investigated using 1/12.5 degrees and 1/25 degrees simulations that are forced by both atmospheric analysis fields and the astronomical tidal potential. The paper examines whether PSI occurs in the model, and whether it accounts for a significant fraction of the tidal baroclinic energy loss. Using energy transfer calculations and bispectral analyses, evidence is found for PSI around the critical latitudes of the tides. The intensity of both diurnal and semidiurnal PSI in the simulations is greatest in the upper ocean, consistent with previous results from idealized simulations, and quickly drops off about 5 degrees from the critical latitudes. The sign of energy transfer depends on location; the transfer is positive (from the tides to subharmonic waves) in some locations and negative in others. The net globally integrated energy transfer is positive in all simulations and is 0.5%-10% of the amount of energy required to close the baroclinic energy budget in the model. The net amount of energy transfer is about an order of magnitude larger in the 1/25 degrees semidiurnal simulation than the 1/12.5 degrees one, implying the dependence of the rate of energy transfer on model resolution.
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Date Issued
2018-06-01
Identifier
FSU_libsubv1_wos_000437215800012, 10.1175/JPO-D-17-0164.1
Format
Citation
Impact of Parameterized Internal Wave Drag on the Semidiurnal Energy Balance in a Global Ocean Circulation Model
Title
Impact of Parameterized Internal Wave Drag on the Semidiurnal Energy Balance in a Global Ocean Circulation Model.
Creator
Buijsman, Maarten C., Ansong, Joseph K., Arbic, Brian K., Richman, James G., Shriver, Jay F., Timko, Patrick G., Wallcraft, Alan J., Whalen, Caitlin B., Zhao, ZhongXiang
Abstract/Description
The effects of a parameterized linear internal wave drag on the semidiurnal barotropic and baroclinic energetics of a realistically forced, three-dimensional global ocean model are analyzed. Although the main purpose of the parameterization is to improve the surface tides, it also influences the internal tides. The relatively coarse resolution of the model of similar to 8 km only permits the generation and propagation of the first three vertical modes. Hence, this wave drag parameterization...
Show moreThe effects of a parameterized linear internal wave drag on the semidiurnal barotropic and baroclinic energetics of a realistically forced, three-dimensional global ocean model are analyzed. Although the main purpose of the parameterization is to improve the surface tides, it also influences the internal tides. The relatively coarse resolution of the model of similar to 8 km only permits the generation and propagation of the first three vertical modes. Hence, this wave drag parameterization represents the energy conversion to and the subsequent breaking of the unresolved high modes. The total tidal energy input and the spatial distribution of the barotropic energy loss agree with the Ocean Topography Experiment (TOPEX)/Poseidon (TPXO) tidal inversion model. The wave drag overestimates the high-mode conversion at ocean ridges as measured against regional high-resolution models. The wave drag also damps the low-mode internal tides as they propagate away from their generation sites. Hence, it can be considered a scattering parameterization, causing more than 50% of the deep-water dissipation of the internal tides. In the near field, most of the baroclinic dissipation is attributed to viscous and numerical dissipation. The far-field decay of the simulated internal tides is in agreement with satellite altimetry and falls within the broad range of Argo-inferred dissipation rates. In the simulation, about 12% of the semidiurnal internal tide energy generated in deep water reaches the continental margins.
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Date Issued
2016-05
Identifier
FSU_libsubv1_wos_000376153100001, 10.1175/JPO-D-15-0074.1
Format
Citation
Semidiurnal Internal Tide Energy Fluxes And Their Variability In A Global Ocean Model And Moored Observations
Title
Semidiurnal Internal Tide Energy Fluxes And Their Variability In A Global Ocean Model And Moored Observations.
Creator
Ansong, Joseph K., Arbic, Brian K., Alford, Matthew H., Buijsman, Maarten C., Shriver, Jay F., Zhao, Zhongxiang, Richman, James G., Simmons, Harper L., Timko, Patrick G.,...
Show moreAnsong, Joseph K., Arbic, Brian K., Alford, Matthew H., Buijsman, Maarten C., Shriver, Jay F., Zhao, Zhongxiang, Richman, James G., Simmons, Harper L., Timko, Patrick G., Wallcraft, Alan J., Zamudio, Luis
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Abstract/Description
We examine the temporal means and variability of the semidiurnal internal tide energy fluxes in 1/25 degrees global simulations of the Hybrid Coordinate Ocean Model (HYCOM) and in a global archive of 79 historical moorings. Low-frequency flows, a major cause of internal tide variability, have comparable kinetic energies at the mooring sites in model and observations. The computed root-mean-square (RMS) variability of the energy flux is large in both model and observations and correlates...
Show moreWe examine the temporal means and variability of the semidiurnal internal tide energy fluxes in 1/25 degrees global simulations of the Hybrid Coordinate Ocean Model (HYCOM) and in a global archive of 79 historical moorings. Low-frequency flows, a major cause of internal tide variability, have comparable kinetic energies at the mooring sites in model and observations. The computed root-mean-square (RMS) variability of the energy flux is large in both model and observations and correlates positively with the time-averaged flux magnitude. Outside of strong generation regions, the normalized RMS variability (the RMS variability divided by the mean) is nearly independent of the flux magnitudes in the model, and of order 23% or more in both the model and observations. The spatially averaged flux magnitudes in observations and the simulation agree to within a factor of about 1.4 and 2.4 for vertical mode-1 and mode-2, respectively. The difference in energy flux computed from the full-depth model output versus model output subsampled at mooring instrument depths is small. The global historical archive is supplemented with six high-vertical resolution moorings from the Internal Waves Across the Pacific (IWAP) experiment. The model fluxes agree more closely with the high-resolution IWAP fluxes than with the historical mooring fluxes. The high variability in internal tide energy fluxes implies that internal tide fluxes computed from short observational records should be regarded as realizations of a highly variable field, not as "means" that are indicative of conditions at the measurement sites over all time.
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Date Issued
2017-03
Identifier
FSU_libsubv1_wos_000400678900015, 10.1002/2016JC012184
Format
Citation