The Integrated Marine Observing System (IMOS) via the AODN Portal has created a single access point for marine data published by AODN contributors. The Portal incorporates a catalogue of metadata, a search interface driven by facets utilising controlled vocabulary terms, and a map interface that can be used to interact with AODN datasets and offers data download in a number of formats.
In the Data Deep Dive Series the Australian Ocean Data Network (AODN) will look at collections on the AODN Portal, describe the collection, give examples of current use and science and illustrate how the data can be obtained. Initially this will be for three collections over as many months.
In the research article “Observed bottom boundary layer transport and uplift on the continental shelf adjacent to a western boundary current” published in 2014, Amandine Schaeffer from the University of New South Wales has used temperature data from two IMOS coastal moorings located near Coffs Harbour.
Figure 1: Temporal evolution of temperature through the water column for two moorings off the coast of New South Wales. Supplied by Amandine Schaeffer.
The temporal evolution of temperature through the water column is shown for each mooring off Coffs Harbour (NSW), namely CH070 above the 70m isobath, approximately 16km from the coast, and CH100, above the 100m isobath and 26km from the coast. Note that the moorings have no surface expression to avoid interaction with boat traffic which is locally heavy. Instead, satellite sea surface temperature is plotted at the surface showing good agreement with the temperature variability at depth.
The majority of the temperature variability is due to the seasonal cycle, wind forcing and the intermittent intrusions of the East Australian Current (EAC) when it meanders towards the coast. Wind-driven upwelling are evidenced by episodes of cold water intruding into the surface layers (e.g. November 2012) in response to northerly winds. Episodes of EAC current encroachment (e.g. March 2010) appear as intense southward depth-averaged velocities (negative along-shelf), warm surface waters (since the EAC transports tropical waters poleward), and cold water intrusions in the bottom boundary layers (black contours).
The data presented in the research article has been collected by the National Mooring Network and is a subset of the following dataset collection “IMOS – Australian National Mooring Network (ANMN) facility – Temperature and salinity time-series” made freely available through the AODN Portal.
The National Mooring Network is a series of national reference stations and regional moorings designed to monitor particular oceanographic phenomena in Australian coastal ocean waters. All coastal moorings are collecting temperature data at several different depths using a range of different instruments. Most of the instruments measure temperature and pressure while for the ones only measuring temperature, the depth is computed from surrounding instruments during the processing step with the Matlab Toolbox.
The data is then stored in netCDF format. Each netCDF file contains data for a single instrument and for a single deployment.
For the two moorings used in the research article, it represents around 390 netCDF files across 43 deployments for the platform called CH070 and around 520 netCDF files across 41 deployments for the platform called CH100.
While all the data is available on the AODN Portal and on the THREDDS catalogue (see next paragraph on how to access it), the user has to do some further data processing in order to stitch the data across deployments and produce a plot like in figure 1.
Recently, the AODN has updated a python script to generate a temperature re-gridded product for all IMOS moorings.
The data is gridded temporally and spatially with a resolution of 60 minutes and a vertical resolution of 1 metre. The vertical extent may vary across deployments depending on the design of the mooring and the location of instruments along the mooring line.
By downloading this data product, the number of data files is reduced dramatically from 500 to around 40 netCDF files for the CH100 mooring for example. Moreover, the visualisation of 10 years of data is then simplified with the temporal and vertical grid applied to the data.
Where can I get it!
The AODN Portal
The AODN Portal is a single access point for marine data published by AODN contributors, including data collected by the Integrated Marine Observing (IMOS) National Mooring Network.
The AODN Portal is a 3-stage process to accessing data:
1. Select a Data Collection: search collections by parameter, organisation, platform and/or date and location,
2. Create a Subset of chosen data collections,
3. Download the selected data collection subsets.
In Step 1 any one of the facets or the keyword search can be used to search and find a collection. The following is one example for finding the IMOS National Mooring Network collections - from the ‘Platform’ facet select ‘Mooring and buoy’ > then select ‘Mooring’, currently 19 Mooring Collections will be displayed.
Direct links to the data collections on the AODN Portal -
IMOS Thredds Catalogue
The netCDF files are available on the IMOS THREDDS catalogue. Data files collected on coastal moorings are organised by Facility then Platform and finally by data product.
Taking the example of the Coffs Harbour CH100 mooring highlighted in figure 1, the individual netCDF files for each instrument and each deployment will be available in:
The corresponding temperature gridded product is available here: