Delayed-mode quality control of oxygen, nitrate and pH data on SOCCOM
biogeochemical profiling floats
Abstract
The Southern Ocean Carbon and Climate Observations and Modeling (SOCCOM)
project has deployed 194 profiling floats equipped with biogeochemical
(BGC) sensors, making it one of the largest contributors to global
BGC-Argo. Post-deployment quality control of float-based oxygen,
nitrate, and pH data is a crucial step in the processing and
dissemination of such data, as in-situ chemical sensors remain in early
stages of development. In-situ calibration of chemical sensors on
profiling floats using atmospheric reanalysis and empirical algorithms
have been shown to bring accuracy to within 3 μmol O2 kg-1, 0.007 pH
units, and 0.5 μmol NO3- kg-1. Routine quality control efforts utilizing
these methods can be conducted manually through visual inspection of
data to assess sensor drifts and offsets, but more automated processes
are preferred to support the growing number of BGC floats and reduce
subjectivity among delayed-mode operators. Here we present a methodology
and accompanying software designed to easily visualize float data
against select reference datasets and assess quality control adjustments
within a quantitative framework. The software is intended for global use
and has been used successfully in the post-deployment calibration and
quality control of over 250 BGC floats, including all within the SOCCOM
array. Results from validation of the proposed methodology are also
presented which can provide a metric for tracking data adjustment
quality through time.