Moored instrument data
The CLIVAR Moored Instrument Data Assembly Centre (MIDAC) is located at BODC and was established in 2004. Our mandate is to acquire, quality control, archive and deliver the moored instrument data collected during CLIVAR. Our aim is to expand the high quality moored instrument data set which was collected during WOCE (World Ocean Circulation Experiment). We will ensure the long-term safeguarding of the data which will be made readily available online.
BODC has extensive expertise in handling moored instrument data and has maintained a Current Meter Inventory for over 20 years.
The MIDAC deals with moored time series data in delayed mode, rather than data from real time observing systems. Moorings may consist of instruments which make fixed point measurements such as conventional current meters or instruments such as Acoustic Doppler Current Profilers (ADCPs) which measure parameters (e.g. current velocity) at multiple depths through the water column. We also handle other types of moored instrument such as thermistor chains or sediment traps.
Data are received directly from the principal investigators after the mooring has been recovered. All incoming data go through standard BODC quality control procedures to bring them up to a consistent standard. The data are converted to a common format (netCDF) and then screened using in-house graphical software.
Currently data are available on request but will later be distributed via this web site.
Data which were not collected specifically for CLIVAR may also be included (CLIVAR-relevant data). Any deep water moored instrument data which are not currently readily accessible may be seen as a valid contribution to CLIVAR. All principal investigators are encouraged to submit their moored instrument data so that it can be preserved and made available.
Uses of moored instrument data
Moored arrays of current meters are essential for obtaining direct measurements of ocean current structure. Data can be used to determine velocities, transports and fluxes of defined currents or throughflows and their variability. These provide valuable information for model validation, property flux calculations, and for comparison with geostrophic, ADCP and altimeter-derived velocities where they are coincident. Estimates of heat flux across hydrographic sections require accurate determination of the western boundary currents. Single moorings and incoherent (spacing larger than the mesoscale) large-scale arrays can provide insights into the vertical structure and variability of the eddy field.
The duration that moored instruments can remain in the water is dependent on the battery life and frequency of sampling as well as being constrained by the logistics (ship availability) for deployment and recovery. Typically arrays are deployed for one or two years at a time, and may be repeatedly recovered and re-deployed to obtain the long temporal coverage required for variability studies.
Other sources of mooring data
CLIVAR also sponsors the tropical moored buoy network. This consists of three arrays including the Tropical Atmosphere Ocean (TAO) and Triton arrays in the Pacific, and the Pilot Research Moored Array in the Tropical Atlantic (PIRATA). Data are available on-line from the Pacific Marine Environmental (PMEL) Laboratory of NOAA in near real time including variables such as temperature, wind, rainfall and salinity. ADCP data are available after the moorings have been recovered. Real-time telemetry of upper ocean currents from point Doppler current meters are under development.
An observing system of moorings, OceanSITES (OCEAN Sustained Interdisciplinary Timeseries Environment observation System) is also being developed under recommendation from the Ocean Observations Panel for Climate (OOPC), together with the CLIVAR Ocean Observations Panel.
Other CLIVAR DACs
A network of CLIVAR Data Assembly Centres (most of which were active during WOCE) are dealing with the different data types. Some of these DACs operate in real-time. The DACs will work together to ensure integration across data streams and to improve methods of data dissemination.