A New-Generation Internal Tide Model Based on 30 Years of Satellite Sea
Surface Height Measurements: Multiwave Decomposition and Isolated Beams
Abstract
A new-generation internal tide model ZHAO30yr is constructed using 30
years of sea surface height measurements from 1993 to 2022 made by 15
satellite altimetry missions. The model contains 8 mode-1 constituents
(M2, S2, N2, K2, K1, O1, P1 and Q1) and 4 mode-2 constituents (M2, S2,
K1 and O1). These constituents are respectively extracted by the same
mapping technique that consists of two rounds of plane wave analysis
with a spatial bandpass filter in between. Their prerequisite
wavelengths are calculated from climatological annual-mean hydrographic
profiles in the World Ocean Atlas 2018. Model errors are estimated to be
0.5-1 mm for all semidiurnal and diurnal constituents. The model is
evaluated using 1 year of independent altimetry data in 2023. The global
internal tide field is decomposed into multiconstituent multimodal
multidirectional internal waves. Multiwave decomposition reveals
unprecedented new features previously masked by multiwave interference.
Numerous long-range internal tidal beams are observed to be associated
with notable topographic features. Semidiurnal beams off the Amazon
shelf and diurnal beams in the Arabian Sea are studied in detail. The M2
and K1 internal tide constituents are examined for their multiwave
decomposition and isolated beams on a global scale.