Tidal Statistics for Australia (Tidal range, LAT, HAT, MLWS, MHWS, Percentiles) derived from the EOT20 tidal model (NESP MaC 3.17, AIMS)

This dataset is a set of raster tidal statistics for the Australian region at a 1/32 degree resolution derived from the EOT20 global tidal model. This dataset provides rasters for Lowest Predicted Tide (LPT), Highest Predicted Tide (HPT), Mean Low Spring Water (MLSW), Mean High Spring Water (MHSW), tidal range (HPT-LPT), tidal percentiles (1, 2, 5, 10, 20, 50, 80, 90, 95, 98, 99) and monthly climatologies (median over all simulated years for a given month) of LPT, Mean, and HPT. 

Lowest Predicted Tide is a proxy for Lowest Astronomical Tide (LAT) and Highest Predicted Tide is a proxy for Highest Astronomical Tide (HAT) estimated over a shorter simulation period of typically 5 years. 

The tidal modelling statistics are all represented as GeoTiff images to allow easy use in subsequent analysis and visualisation in GIS tools. The monthly climatology datasets (LPT, Mean and HPT) are stored as multi-band images with one band per month. The tidal percentiles are also stored as multi-band images with one band per percentile value. 

This dataset also includes a comparison between the EOT20 tidal model and 70 tide gauges around Australia. This includes a comparison of the monthly min, mean and maximum over the last 19 years of data, and a monthly climatology over the full tidal record. Generated plots of the 70 stations comparisons are available in the data download section.

All dataset products and validation analysis were performed using Python scripts, allowing this dataset to be fully reproduced. The source code is available from GitHub. 

Limitations:

This modelling was limited to the accuracy of the EOT20 global model. Tidal statistics were calculated using a 30 minute time increment over a 5-year period (2020-2025) (Note: the initial release data only covered a single year 2023). A simulation period of 19 years is needed to capture the full lunar cycle. The calculation time period was limited due to the high computational cost of processing the full 19 year lunar cycle. Based on reviewing the tide gauge data and the matching tidal predictions we find that in the last 19 years the largest tidal ranges occurred in 2004 - 2006 and 2021 - 2024 and the lowest tidal range were in the middle of this period from 2012 - 2014. By modelling from 2020-2025 the statistics are based on the period of the cycle with the highest tidal ranges. 

The EOT20 tidal model provides tidal constituents on a grid that is 1/8 degree in resolution. Land areas pixels are excluded from the model grid. This means that nearshore areas, particularly those associated with river mouths or bays, are excluded from the model. In this dataset we infill these areas based on model parameters extrapolated using nearest neighbour interpolation. This will result in increased error in the tidal estimates in the locations.  

This dataset is not suitable as a tidal datum for administrative and jurisdictional extents. This dataset has not gone through enough validation for its use in critical decisions. It was developed to assist in understanding tidal conditions experienced by shallow marine environments. 

Format: 

GeoTiff raster files (EPSG:4326, 2336 x 1216 pixels, Float32, LZW). One file per statistic. Percentiles contain 11 bands corresponding to 1, 2, 5, 10, 20, 50, 80, 90, 95, 98, and 99 percentile of time exposure. Monthly_LPT, Monthly_Mean, and Monthly_HPT each have 12 bands corresponding to months of the year, where band 1 is January, band 2 is February, etc.

Dataset relevance:

This section aims to improve the discoverability of the dataset by highlighting key areas where this dataset is relevant and what it shows.

This dataset provides a plot of the monthly lowest tide, mean tide and highest tide as a time series and a climatology (where all years are overlaid on each other and the monthly results are taken from the median value of all the results for each month) based on 70 tide gauges (based on data made available through the BOM website) around Australia, with a comparison with the same tidal values predicted from the EOT20 tidal model. This includes the following locations: 
- Queensland: Cape Ferguson, Rosslyn Bay, Booby Island, Bowen, Brisbane Bar, Bundaberg (Burnett Heads), Cairns, Gladstone, Gold Coast Operations Base, Goods Island, Hay Point, Ince Point, Karumba, Lucinda (Offshore), Mackay Outer Harbour, Mooloolaba, Nardana Patches, Mourilyan Harbour, Port Alma, Port Douglas, Shute Harbour, Townsville, Turtle Head, Urangan, Weipa (Humbug Point), Thursday Island
- New South Wales: Port Kembla, Botany Bay, Eden, Lord Howe Island, Newcastle, Norfolk Island, Fort Denison (Sydney), Yamba
- Victoria: Portland, Stony Point, Lorne
- South Australia: Port Stanvac, Thevenard, Port Adelaide (Outer Harbor), Port Giles, Port Lincoln, Port Pirie, Victor Harbor, Wallaroo, Whyalla
- Western Australia: Esperance, Hillarys, Broome, Albany, Bunbury (Inner), Cape Lambert, Carnarvon, Exmouth, Fremantle, Geraldton, King Bay, Onslow, Port Hedland, Wyndham
- Tasmania: Burnie, Spring Bay, Low Head, Mersey River (Devonport)
- Northern Territory: Darwin, Milner Bay - Groote Eylandt
- Indian Ocean: Cocos - Keeling Islands (Home Island)

The tidal range product shows that the strongest tides occur in the Kimberley, in the northern portions of the Pilbara along Eighty Mile Beach, in Joseph Bonaparte Gulf, between Darwin and the Tiwi Islands, and in Broad Sound in Queensland. Areas that have a low tidal range include the coast south of Ningaloo Reef and much of the Gulf of Carpentaria. 

References:

Bishop-Taylor, R., Sagar, S., Phillips, C., &amp; Newey, V. (2024). eo-tides: Tide modelling tools for large-scale satellite earth observation analysis. https://github.com/GeoscienceAustralia/eo-tides

Sutterley, T. C., Alley, K., Brunt, K., Howard, S., Padman, L., Siegfried, M. (2017) pyTMD: Python-based tidal prediction software. 10.5281/zenodo.5555395

Hart-Davis Michael, Piccioni Gaia, Dettmering Denise, Schwatke Christian, Passaro Marcello, Seitz Florian (2021). EOT20 - A global Empirical Ocean Tide model from multi-mission satellite altimetry. SEANOE. https://doi.org/10.17882/79489

Hart-Davis Michael G., Piccioni Gaia, Dettmering Denise, Schwatke Christian, Passaro Marcello, Seitz Florian (2021). EOT20: a global ocean tide model from multi-mission satellite altimetry. Earth System Science Data, 13 (8), 3869-3884. https://doi.org/10.5194/essd-13-3869-2021

Change log:

As updates to this dataset are published, the changes will be recorded here.
- 2025-02-27 v1: Initial release of the dataset that is based on the northern-au-test.yaml. This has a limited spatial extent and 1-year simulation. This is only a spatial subset of the full dataset. This initial release has been archived (https://nextcloud.eatlas.org.au/apps/sharealias/a/AU_NESP-MaC-3-17_AIMS_EOT20-tidal-stats_v1).
- 2025-03-18 v1-1: Release of the full Australian geographic scope calculated over 5 years.

Tags: Australia, Marine
Organization: Australian Ocean Data Network