Comparison of internal gravity wave spectra in high-resolution global simulations with observations
Event: 2017 Ocean Surface Topography Science Team Meeting
Session: Tides, internal tides and high-frequency processes
Presentation type: Type Oral
We present comparisons of the internal gravity wave spectrum in high-resolution global simulations with observations. We use 1/12th and 1/25th degree global simulations of the HYbrid Coordinate Ocean Model (HYCOM), which is used as an operational ocean model by the US Navy, and 1/12th, 1/24th, and 1/48th degree simulations of the Massachusetts Institute of Technology general circulation model (MITgcm) performed on NASA supercomputers. Both the HYCOM and MITgcm simulations have simultaneous atmospheric and tidal forcing, implying that near-inertial waves and internal tides are produced. The high vertical and horizontal resolution of these simulations allows for nonlinear interactions, which fill out an internal gravity wave spectrum. We compare the frequency spectra of kinetic energy and temperature variance in the models with spectra compared from historical moored observations, at more than a thousand instrument locations. We compare the dynamic height variance, the vertical wavenumber-frequency spectrum of kinetic energy, and the vertical wavenumber spectrum of density variance, in models versus moored McLane Profiler observations. We find that the models compare more closely with observations, and with predictions of the Garrett-Munk spectrum, as model resolution increases. Regional simulations conducted with global model forcing along the boundaries indicate that both horizontal and vertical resolution need to be increased to further improve model-data comparisons.