Every observation carries a data descriptor, which is how you find out whether anyone is actually using your data.
| Flag | Meaning |
|---|---|
| Z | Preliminary, no QC applied |
| C | Coarse: passed level 1 validity |
| S | Screened: passed levels 1 and 2 (internal, temporal, statistical-spatial consistency) |
| V | Verified: passed levels 1 through 3, including spatial consistency |
| Q | Questioned: passed level 1, failed 2 or 3 |
| X | Rejected: failed level 1 |
To be useful to forecasters your observations need to reach S or V. Level 2 includes the internal consistency check that fails you when dewpoint exceeds temperature, plus a statistical-spatial check that flags stations failing most of the time over the preceding week.
To check your own flags, see the validation tools in Install, commission and maintain.