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Cabled observatories will produce long time series of real time physical ocean data -- revealing: Trends Long-period fluctuations (>1 year) Events But, without sensor drift histories and laboratory inter-calibration, trends and events will be lost in: Sensor drift Calibration variability.
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Cabled observatories will produce long time series of real time physical ocean data -- revealing: Trends Long-period fluctuations (>1 year) Events But, without sensor drift histories and laboratory inter-calibration, trends and events will be lost in: Sensor drift Calibration variability Data Quality Issues
Data Quality Issues • Accurate real time temperature data is easily achieved -- drift rates are typically 0.002 °C/year • Accurate real time conductivity and oxygen data is more difficult to achieve: • Conductivity and oxygen are subject to fouling – especially at shallow depths • Polarographic oxygen sensors drift even before deployment
Calibration Policies • ARGO program: careful handling minimizes these problems in deep deployments • Most accurate time series will still require: • Post deployment processing to correct drift • Comprehensive plan for sensor calibration • Conversion of data to scientific units will be performed on shore
Recommendations • Establish comprehensive calibration plan: • Pre-deployment and post deployment calibrations • Inter-lab comparisons • Maintain sensor calibration history as part of the data library • Associate or attach this drift history to unprocessed data