Validating the spatial variability in the semidiurnal internal tide in a realistic global ocean simulation with Argo and mooring data

Abstract

The autocovariance of the semidiurnal internal tide (IT) is examined in a 32d segment of a global run of the HYbrid Coordinate Ocean Model (HYCOM). This numerical simulation, with 41 vertical layers and 1/25 horizontal resolution, includes tidal and atmospheric forcing, allowing for the generation and propagation of ITs to take place within a realistic eddying general circulation. The HYCOM data are in turn compared with global observations of the IT around 1000dbar, from Argo float park-phase data and mooring records. HYCOM is found to be globally biased low in terms of the IT variance and decay of the IT autocovariance over timescales shorter than 32d. Except in the Southern Ocean, where limitations in the model cause the discrepancy with in situ measurements to grow poleward, the spatial correlation between the Argo and HYCOM tidal variance suggests that the generation of low-mode semidiurnal ITs is globally well captured by the model.