An Oceanic General Circulation and Tide Model in Orthogonal Curvilinear Coordinates

An oceanic general circulation and tide model (OGCTM) is documented and tested. The OGCTM is an offspring of the ocean model at Max Planck Institute for Meteorology, of which is framed in the orthogonal curvilinear coordinates. In this model, the realtime tidal potential algorithm based on lunisolar ephemeredes is implemented, which calculates the realtime lunisolar ephemeredes according to the position of sun and moon. The dynamical component of the inverted barometer is introduced to establish the sea level responds to changing atmospheric pressure, which is of the same magnitude as the residual orbital error in primary basins but can be quite substantial in shallow marginal seas due to the amplified response in shallow regions. In the momentum equations the reduction of Earth tides are accounted for by the Love numbers and the effect of ocean tide loading and self-attraction is introduced basing on a scalar approximation. The validation using harmonic analysis in arbitrary selected model year indicates that the OGCTM successfully reproduces the main oceanic amphidromic systems in the world ocean. Compared to the observations of MEOM-ST103 dataset, which includes harmonic constants of 103 selected island and pelagic tide gauges suggest that the OGCTM is robust even in comparison to the pure barotropical tide model containing data assimilation scheme. A study using the OGCTM in comparison to the ocean model of Max Planck Institute for Meteorology is done for the global ocean circulation field, especially in the North Atlantic. The experiments are designed as two 56-year control runs forced with daily NCEP reanalysis surface flux dataset, respectively. Changes in both models are found and discussed. Emphasis in this article is to introduce the model and investigate the impact of tidal potential on the global ocean circulation field.