- Title
- Development of a regional barotropic ocean tide model for northeast Australian coastal zones
- Creator
- Seifi, Fardin
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2020
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- This research aims at developing a regional assimilation barotropic tidal model for the Great Barrier Reef (GBR) and Coral Sea, Australia. For this, all available satellite altimeter, coastal and marine datasets have been used to constrain the shallow water tidal equations in order to estimate tidal constants for 37 long-period, major and shallow water constituents. The resulting model is called University of Newcastle Great Barrier Reef (UoNGBR) model that has a spatial resolution of 2' x 2'. In this process the recent bathymetry model gbr100 with spatial resolution of 3.6" x 3.6" is used as the source of depth information for the assimilation model. In addition, in order to address the role of reefs in shaping tidal regime of the area, spatially variable drag coefficients are adopted from the GBR1 Hydrodynamic Model. According to GBR1 model, drag coefficient varies from 0.0025 to 0.0049 in the GBR and Coral Sea. The modelling procedure is split into three main phases: (1) assessment of the performance of existing tidal models, (2) development of an empirical tidal model, and (3) tidal assimilation procedure. According to the assessment results, all existing tidal models show large uncertainties in the central and southern GBR, where complex bathymetry and coral reefs exist. Therefore, an assimilation approach is selected to develop the tidal model, with consideration of the effect of bathymetry and sea bottom complexities. The Oregon state university Tidal Inversion Software (OTIS) is chosen for this purpose. The OTIS has an efficient algorithm and can handle all different input data including information from sea current meters. To provide OTIS with the initial values needed in its forward solution, an empirical tidal model is developed based on Remove-Compute-Restore method for the GBR and Coral Sea. In order to create the empirical tidal model, tide gauge data is directly analysed using a harmonic analysis to extract tidal constants for 37 components, while the Remove-Compute-Restore method is used for satellite altimetry observations. The FES2014 model, which has implemented more tidal constituents in comparison to other existing models, is used as the background model. The calculated Sea Level Anomalies (SLAs) are analysed using a combination of the harmonic analysis and response method to estimate the tidal constant corrections. The estimated tidal constants are spread over a regular 2' x 2' grid using a depth dependent Least Squares Collocation (LSC) method. This empirical model is used in calculation of the forward solution in OTIS software. The estimated tidal constituents through analysing data from coastal tide gauges, altimetry (including only pure ocean tides) and current meters are used as the open boundary conditions, which are assimilated into the tidal shallow water equations using OTIS software. A sensitivity analysis is performed to investigate how bathymetry and drag coefficients affect the assimilation model. The results reveal that the use of the high-resolution bathymetry model gbr100 and spatially variable drag coefficients makes a significant contribution to the accurate estimation of major tidal constituents. The resulting University of Newcastle Great Barrier Reef (UoNGBR) model shows major improvements in the central and southern GBR, where other models are inaccurate due to highly variable bottom topography and presence of coral reefs. The UoNGBR outperforms TPXO assimilation models, which are also developed using OTIS, with root mean square (RMS) differences of ~10, ~9 and ~2 cm at the coastline and in coastal and shelf zones, respectively. The UoNGBR is also more favourable than FES2012, which was known to be the best model in phase 1 of the model assessment process, with the mean RMS differences of ~5 and ~1.5 cm, respectively, at the coastline and in the coastal zone.
- Subject
- Great Barrier Reef; barotropic tidal model; UoNGBR; FORTRAN
- Identifier
- http://hdl.handle.net/1959.13/1417368
- Identifier
- uon:37199
- Rights
- Copyright 2020 Fardin Seifi
- Language
- eng
- Full Text
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | ATTACHMENT01 | Thesis | 11 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 523 KB | Adobe Acrobat PDF | View Details Download |