Argo Real-time Quality Control Process

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Argo Real-time Quality Control Process

• NOAA/AOML Y.-H. DANESHZADEH,
• R. MOLINARI, R. SABINA, C. SCHMID
• CIMAS/UM E. FORTEZA, X. XIA, H. YANG

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Guiding Philosophy of the international real-time
DACs

• PROVIDE TO THE INTERNATIONAL OPERATIONAL AND
  RESEARCH
• OCEANIC COMMUNITIES PROFILES OF TEMPERATURE AND
  SALINITY
• RESULTING FROM ARGO FLOATS THAT MEET THE
  FOLLOWING
• CRITERIA
• DATA HAVE BEEN MANAGED IN A UNIFORM MANNER
• DATA ARE FREE
• DATA ARE READILY ACCESSIBLE
• DATA ARE AVAILABLE WITHIN A TIMELY MANNER
• DATA HAVE BEEN QUALITY CONTROLLED TO REMOVE THE
  MOST
• EGREGIOUS ERRORS
• COST OF REAL TIME QUALITY CONTROL IS REASONABLE

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Number of profiles quality controlled per year
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Atlantic Data Coverage
Positions of the floats that have delivered data
within the last 30 days
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How an Argo float works
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Data flow
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Real-time processing system
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Delayed-mode processing system
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Delayed-mode processing system
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Automatic quality control

1. Platform Identification
2. Impossible Date (valid not before 1997)
3. Impossible Location (-180 to 180, -90 to 90)
4. Position on Land (ETOPO5)
5. Impossible Speed (lt3m/s)
6. Global Range (-2.5 to 40C, 0 to 41 psu)
7. Regional Range (Red Sea, Mediterranean Sea)
8. Pressure Increasing
9. Spike ( V2 - (V3 V1)/2 - (V3 - V1) / 2 )

Documents are at http//www.ifremer.fr/coriolis/cd
c/argo_rfc.htm
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Regional Range tests, definitions
Red Sea Temperature in range 21.7 to 40.0oC
Salinity in range 0.0 to 41.0 Mediterranean
Sea Temperature in range 10.0 to 40oC
Salinity in range 0.0 to 40.0
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Spike test examples
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Automatic quality control

• Top and Bottom Spike (no top spike test, bottom
  spike test currently under development)
• Gradient ( V2 - (V3 V1)/2 )
• Digit Rollover test (part of decoders)
• Stuck Value (e.g. all values of T the same)
• Density Inversion (gradient must be gt0)
• Grey List (decided by PI Operator)
• Gross Salinity or Temperature Sensor Drift Test
  (checks if values in the deep ocean change too
  much, dT gt1oC, dS gt0.5 psu)

Documents are at http//www.ifremer.fr/coriolis/cd
c/argo_rfc.htm
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Bottom spike examples
Currently no test is available to detect this
problem.
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Gradient test examples
If spikes are not excluded prior to application,
then the test may flag some good points as bad.
salinity
level
salinity
level
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Density inversion test examples
Current version top to bottom.
Flags wrong point because of three bad values
around a good one.
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Density inversion test examples
New version top to bottom and bottom to top.
One flag at wrong point because of three bad
values around a good one.
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Automatic quality control

1. Visual QC at AOML currently triggered by failure
   of any of the other tests on the profile data
   (except for grey list test). Additionally
   triggered by climatology/reanalysis test.
2. Frozen profile (gt5 almost identical consecutive
   profiles).
3. Deepest pressure test pressure may not exceed
   nominal profile pressure given in the meta file
   by more than 10.

Documents are at http//www.ifremer.fr/coriolis/cd
c/argo_rfc.htm
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Visual quality control
Two cases of bad profiles that can not be
detected by the standard Argo QC tests. For these
a climatology test that triggers a visual QC can
be very helpful.
temperature
level
salinity
level
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Results of frozen profile test
Blue circles indicate that T (top) or S (bottom)
failed the test.
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Quality control statistics
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Quality control statistics
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US Argo DAC web page at AOML
http//www.aoml.noaa.gov/phod/ARGO/HomePage