The K1 internal tide simulated by a 1/10° OGCM

This paper quantifies the K-1 internal tide simulated by the 1/10 degrees STORMTIDE model, which simultaneously resolves the eddying general circulation and tides. An evident feature of the K-1 internal tide is the critical latitude phi(c) at 30 degrees, which in the STORMTIDE model is characterized by variations from a high energy level equatorward of 30 degrees to a low energy level poleward of 30 degrees. This critical latitude separates the internal tide dynamics into bottom-trapped (at latitudes vertical bar phi vertical bar > vertical bar phi(c)vertical bar) and freely propagating (at vertical bar phi vertical bar < vertical bar phi(c)vertical bar) motions, respectively. Both types of motions are examined. The bottom -trapping process reveals a gradual vertical decrease of wave energy away from the bottom. The vertical scale, over which the wave energy decrease occurs, is smaller in shallow than in deep water regions. For the freely propagating K-1 internal tides, the STORMTIDE model is able to simulate the first three low modes, with the wavelengths ranging from 200-400 km, 100-200 km, to 60-120 km. These wavelength distributions reveal not only a zonal asymmetry but also a poleward increase up to phi(c), in particular in the Pacific. Such distributions indicate the impact of stratification N and the Coriolis frequency f on the wavelengths. The large wavelength gradient near phi(c) is caused by the wavelength increase from finite values at subcritical latitudes to infinity at phi(c). Compared to the M-2 internal tide, the lower K-1 tidal frequency leads to a stronger role of f, hence a weaker effect of N, for the K-1 internal tide. (C) 2017 Elsevier Ltd. All rights reserved.