A new-generation internal tide model based on 30 years of satellite sea surface height measurements: multiwave decomposition and isolated beams
<p>An internal tide model, ZHAO30yr, is developed using 30 years of satellite altimetry sea surface height (SSH) measurements from 1993 to 2022 by a recently improved mapping technique that consists of two rounds of plane wave analysis with a spatial bandpass filter in between. Prerequisite wa...
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2025-08-01
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| Series: | Earth System Science Data |
| Online Access: | https://essd.copernicus.org/articles/17/3949/2025/essd-17-3949-2025.pdf |
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| Summary: | <p>An internal tide model, ZHAO30yr, is developed using 30 years of satellite altimetry sea surface height (SSH) measurements from 1993 to 2022 by a recently improved mapping technique that consists of two rounds of plane wave analysis with a spatial bandpass filter in between. Prerequisite wavelengths are calculated using climatological annual mean hydrographic profiles in the World Ocean Atlas 2018. ZHAO30yr only extracts the 30-year phase-locked internal tide component, lacking the incoherent component caused by the time-varying ocean environment. The model contains 12 internal tide constituents: eight mode-1 constituents (<span class="inline-formula"><i>M</i><sub>2</sub></span>, <span class="inline-formula"><i>S</i><sub>2</sub></span>, <span class="inline-formula"><i>N</i><sub>2</sub></span>, <span class="inline-formula"><i>K</i><sub>2</sub></span>, <span class="inline-formula"><i>K</i><sub>1</sub></span>, <span class="inline-formula"><i>O</i><sub>1</sub></span>, <span class="inline-formula"><i>P</i><sub>1</sub></span>, and <span class="inline-formula"><i>Q</i><sub>1</sub></span>) and four mode-2 constituents (<span class="inline-formula"><i>M</i><sub>2</sub></span>, <span class="inline-formula"><i>S</i><sub>2</sub></span>, <span class="inline-formula"><i>K</i><sub>1</sub></span>, and <span class="inline-formula"><i>O</i><sub>1</sub></span>). Model errors are estimated to be lower than 1 mm in the SSH amplitude on global average, thanks to the long data record and improved mapping technique. The model is evaluated by making internal tide correction to independent altimetry data for 2023. A total of 10 constituents (but for <span class="inline-formula"><i>K</i><sub>2</sub></span> and <span class="inline-formula"><i>Q</i><sub>1</sub></span>) can reduce variance on global average. <span class="inline-formula"><i>K</i><sub>2</sub></span> and <span class="inline-formula"><i>Q</i><sub>1</sub></span> can only cause variance reductions in their source regions. The model decomposes the multiconstituent, multimodal, multidirectional internal tide field into a series of simple 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 show numerous long-range internal tidal beams associated with notable topographic features. The semidiurnal internal tidal beams off the Amazon shelf and the diurnal internal tidal beams in the Arabian Sea are examined in detail. ZHAO30yr is available at <a href="https://doi.org/10.6084/m9.figshare.28078523">https://doi.org/10.6084/m9.figshare.28078523</a> <span class="cit" id="xref_paren.1">(<a href="#bib1.bibx84">Zhao</a>, <a href="#bib1.bibx84">2024</a><a href="#bib1.bibx84">b</a>)</span>. Model errors are available at <a href="https://doi.org/10.6084/m9.figshare.28559978.v3">https://doi.org/10.6084/m9.figshare.28559978.v3</a> <span class="cit" id="xref_paren.2">(<a href="#bib1.bibx85">Zhao</a>, <a href="#bib1.bibx85">2025</a>)</span>.</p> |
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| ISSN: | 1866-3508 1866-3516 |