About AusWaves

Overview

Australia’s Integrated Marine Observing System (IMOS) has recently established the new Coastal Wave Buoys facility. This facility collects essential data for understanding coastal processes and changes driven by waves and ocean water temperature. Accurate observations of these parameters are required to verify and improve marine forecasts, inform marine operations and recreation, and form the basis for an improved understanding of ocean and coastal processes.

The IMOS Coastal Wave Buoys facility complements the existing network of offshore and nearshore wave buoys that are deployed around Australia and maintained by a variety of federal and state government agencies as well as university research groups. The central IMOS Coastal Wave Buoys facility is based at The University of Western Australia but is comprised of a network of regional sub-facilities based in each state. The data included here is a compilation of near real-time data from sites supported by both IMOS and other organisations who provide their data.

This website has been designed to display the near real-time data collected by these surface wave buoys and to allow download of all archived data. Our wave data is available via in near real-time and delayed mode (processed data from onboard memory cards) via the IMOS Australian Ocean Data Network (AODN). See below for more details on data processing and availability.

Australia’s Integrated Marine Observing System (IMOS) is enabled by the National Collaborative Research Infrastructure Strategy (NCRIS). IMOS acknowledges the Traditional Custodians and Elders of the land and sea on which we work and observe, and recognise them as Australia’s first marine scientists and carers of Sea Country. We pay our respects to Aboriginal and Torres Strait Islander peoples past and present.

Check out how some of our data has been used around Australia!

Instrumentation and Mooring Design

The IMOS Coastal Wave Buoys facility utilises Sofar Ocean’s Spotter wave buoy to collect surface wave data. The Sofar Spotter is a 0.4 m diameter wave buoy that utilizes a GNSS (aka GPS) receiver to derive the buoy’s horizontal and vertical displacements. These displacement data are then processed assuming the buoy follows the ocean surface using standard spectral processing methods (Kuik et al., 1988). Additional data available on this website are collected using Sofar Ocean’s smart mooring, which relies on the Spotter for wave data but also include additional temperature sensors near the surface and sometimes also at the sea bottom, and a Datawell Waverider Mk4, which is a large format (0.9 m diameter) accelerometer based wave buoy.

The wave buoys are all moored in shallow to intermediate (~15 – 80 m) water depth and follow the mooring guidelines outlined in the Australian Wave Buoy Operations and Data Management Guidelines (Hansen and Kinsela, 2023).

Data Description and Analysis

Surface wave buoys measure their motion at the water surface due to the waves using an accelerometer and/or GNSS receiver. The motions (in both the vertical and horizontal directions) are typically recorded approximately twice a second for a period of 30 to 60 minutes with these data then used to calculate statistics that attempt to represent the wave conditions over this time period. Over a 30- or 60-minute analysis period, there will be waves of many different sizes, of differing periods (the time between successive wave crests) and coming from different directions. To derive parameters that attempt to statistically describe the wave field, the buoy motions are processed using spectral analysis. The most common parameters resulting from this spectral analysis are the:

Significant wave height (Hs) which roughly equates to the average of the largest one-third of the waves recorded in a given analysis period.
Peak period (Tp) and peak direction (Dp) which are the most commonly occurring period and direction of the waves recorded in a given analysis time period (note that for waves and wind the convention is that the direction reported is the direction from).
Mean period (Tm) and direction (Dm) which are the energy-weighted average wave period and direction.
Peak and mean directional spreading which are an indication of how variable the wave directions are. If the directional spreading is small most waves are approaching from the peak/mean direction.

Additional parameters measured by some of the buoys include wind speed and direction as well as surface and bottom water temperature. The Sofar Spotter buoys provide an estimate of the wind speed and direction based on the buoy’s measurement of the short period wind waves (see a more detailed description here). Surface temperatures are recorded by both Datawell and Sofar buoys via a thermistor mounted to the wave buoy hull. Finally, simultaneous surface and bottom temperatures are recorded by Sofar Smart Moorings, which include a surface (~1 m below surface) and near bottom (~1 to 5 m above bottom) temperature sensor incorporated into the mooring.

The above parameters are calculated on-board the buoys and transmitted at 30-minute to 2-hour intervals via 4G or Iriduium satellite internet. Based on the needs of the supporting project (and data transmission budget) some buoys also transmit back more detailed output from the spectral analysis which allows us to calculate (and show on the website) what is called the two-dimensional spectrum (calculated using the maximum entropy estimation method following Lygre and Krogstad, 1986). The two-dimensional spectrum is useful as it allows you to visualize the distribution of wave energy across both period and directional space. In the below example of a two-dimensional spectrum from Torbay near Albany (WA), you can see three distinct regions of wave energy representing different sources, each with separate periods and directions. First, the most energy (red/yellow areas) is arriving from the southwest and has a period of about 11 seconds, these are the dominant conditions at the site when these data were recorded. Second, you can see a patch of energy between 20 and 25 seconds from the south-southwest. This very long period energy is indicative of a new swell arriving from a distant storm in the Southern Ocean. Finally, you can see energy with periods of 10 seconds and less from the south-southeast. The short period of these waves indicates they were mostly likely generated by local winds.

Quality control

Once the data is received by a server at UWA it is run through an automated quality control process to try and identify and remove any bad measurements (for example caused by temporary submergence of a buoy). The automated quality control is completed following the tests detailed in the QARTOD manual for surface waves. When data is downloaded from AUSWAVES (see below), a CSV is generated which contains the quality control flags for wave data (QF_waves), surface temperature (QF_sst), and bottom temperature (QF_bott_temp), where its collected. For all quality flags, the following convention is used: 1 = good data; 2 = not assessed; and 4 = bad data. For all parameters, ‘-9999’ denotes missing data or data that is not collected at a site.

Usage and Data Acquisition

All data on AUSWAVES is available via a Creative Common license (CC BY 4.0). You are welcome to download data the real-time and archived data directly from AUSWAVES by selecting the date range and then clicking ‘export data’. Please follow the Terms and Conditions statement on the download window for how to appropriately acknowledge the data source for each wave buoy (see below). We also ask that you provide some info on where you are based and how you plan to use the data — all other fields are optional.

Both real-time and delayed mode data are available via AODN as part of the ‘Wave buoys Observations – Australia – near real-time’ and ‘Wave buoys Observations – Australia -delayed (National Wave Archive)’ data collections.

We value your feedback — please let us know how you are using this wave data and if you have suggestions on how we can improve things.