This document is the Argo quality control (QC) manual for nitrate concentration, where the metadata parameter name for the state variable is NITRATE with units μmol kg-1. The document describes two levels of quality control:

• The first level is the “real-time” (RT) quality control system, which always includes a set of agreed-upon automatic quality-control tests on each measurement. Data adjustments can also be applied within the real-time system, and quality flags assigned accordingly.
• The second level is the “delayed-mode” (DM) quality control system where data quality is assessed in detail by a delayed-mode operator and adjustments (based on comparison to high-quality reference fields) are derived. As mentioned, these adjustments can then be propagated forward and applied to incoming data in real-time until the next delayed-mode assessment is performed.