A New-Generation Internal Tide Model Based on 30 Years of Satellite Sea Surface Height Measurements

Abstract. An internal tide model ZHAO30yr is developed using 30 years of satellite altimetry sea surface height measurements from 1993 to 2022 by a newly improved mapping technique that consists of two rounds of plane wave analysis with a spatial bandpass filter in between. Prerequisite wavelengths are obtained using climatological annual-mean hydrographic profiles in the World Ocean Atlas 2018. The model contains 12 internal tide constituents: 8 mode-1 constituents (M₂, S₂, N₂, K₂, K₁, O₁, P₁, and Q₁) and 4 mode-2 constituents (M₂, S₂, K₁, and O₁). Model errors are estimated to be lower than 1 mm in amplitude, thanks to the new mapping technique and long data record. The model is evaluated by making internal tide correction to independent altimetry data in 2023. Ten constituents (but for K₂ and Q₁) can reduce variance on global average; K₂ and Q₁ can cause variance reductions in their source regions. The model decomposes the multiconstituent multimodal multidirectional internal tide field into a series of plane waves at each grid point. The decomposition reveals unprecedented features previously masked by multiwave interference. The model divides each internal tide constituent into components by propagation direction. The directionally-decomposed components reveal numerous long-range internal tidal beams associated with notable topographic features. The semidiurnal beams off the Amazon shelf and the diurnal beams in the Arabian Sea are examined in detail. ZHAO30yr is available for download at http://doi.org/10.6084/m9.figshare.28078523 (Zhao, 2024).