Realtime QC

Profile data

We perform the following automated, realtime, quality control checks on all profile data collected by the UK floats. The tests are conducted in the order listed and quality control flags are assigned.

The first 16 tests are standard in Argo data management and are defined in the Argo Quality Control Manual. However BODC implements two additional tests, the profile envelop and the freezing point test. Further information is provided here.

  1. Impossible date — Tests for sensible observation date and time values.
  2. Impossible location — Tests for sensible observation latitude and longitude values.
  3. Position on land — Tests whether the observation position is on land.
  4. Impossible speed — Tests for a sensible distance travelled since the previous profile.
  5. Global range — Tests that the observed temperature and salinity values are within the expected extremes encountered in the oceans.
  6. Regional range — Tests that the observed temperature and salinity values are within the expected extremes encountered in particular regions of the oceans.
  7. Deepest pressure — Tests that the profile does not contain pressures higher than the highest value expected for a float.
  8. Pressure increasing — Tests that pressures from the profile are monotonically increasing.
  9. Spike — Tests salinity and temperature data for large differences between adjacent values.
  10. Gradient — Tests to see if the gradient between vertically adjacent salinity and temperature measurements are too steep.
  11. Digit rollover — Tests whether the temperature and salinity values exceed a floats storage capacity.
  12. Stuck value — Tests for all salinity or all temperature values in a profile being the same.
  13. Density inversion — Tests for the case where calculated density at a higher pressure in a profile is less than the calculated density at an adjacent lower pressure.
  14. Grey list — Tests whether the sensor identifier is present in a list that has been collated to identify sensors which are experiencing problems.
  15. Sensor drift — Tests temperature and salinity profile values for a sudden and important sensor drift.
  16. Frozen profile — Tests for the case where a float repeatedly produces the same temperature or salinity profile (with very small deviations).
  17. Profile envelop — Tests that temperature and salinity profile values are within an envelope of permitted values within depth ranges. On failure the QC test identifier value 2000000000000H is used.
  18. Freezing point — Tests if the profile temperature at a given pressure and salinity is less than the calculated freezing point temperature. On failure the QC test identifier value 4000000000000H is used.

Quality control flags

Flag valueMeaningComment
0No QCNo quality control performed.
1Good dataAll quality control tests passed.
2Probably good data 
3 Bad data. Potentially correctable Test 14 failed, all other tests passed. These data are not to be used without scientific correction.
4Bad data Data have failed one or more tests, excluding test 14.
5Value changed 
8Interpolated value
9Missing value 
Ministry of Defence (MOD)    National Oceanography Centre, Southampton (NOCS)     Met Office     British Oceanographic Data Centre (BODC)     Department for Environment Food and Rural Affairs (Defra)