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Quality control method

ARGO Quality control method

  • 01Platform identification

  • 02Impossible date test

  • 03Impossible location test

  • 04Position on land test

  • 05Impossible speed test

  • 06Global range test

  • 07Regional range test

  • 08Pressure increasing test

  • 09Spike test

  • 10Top and bottom spike test

  • 11Gradient test

  • 12Digit rollover test

  • 13Stuck value test

  • 14Density inversion

  • 15Grey list

  • 16Gross Sal.or temp. sensor drift

  • 17Visual QC

  • 18Frozen profile test

  • 01

    Platform identification

    Every centre handling float data and posting them to the GTS will need to prepare a metadata file for each float and in this is the WMO number that corresponds to each float ptt. There is no reason why, except because of a mistake, an unknown float ID should appear on the GTS.
  • 02

    Impossible date test

    This test requires that the Julian day of a float profile be later than 1st January 1997 and earlier than the current date of the check (in UTC time). Hence if JULD = number of days elapsed since 1st January 1950, then this test checks that 17167 <= JULD < UTC date of check
  • 03

    Impossible location test

    This test requires that the observation latitude and longitude from a float profile be sensible.
    Latitude in range −90 to 90 , Longitude in range −180 to 180
  • 04

    Position on land test

    This test requires that the observation latitude and longitude from a float profile be located in an ocean.
    Use can be made of any topography/bathymetry file that allows an automatic test to check if a position is located on land.
  • 05

    Impossible speed test

    Drift speeds for floats can be generated given the positions and times of the floats when they are at the surface and between profiles.
    In all cases we would not expect the drift speed to exceed 3 ms−1. If
  • 06

    Global range test

    This test applies a gross filter on observed values for pressure, temperature and salinity.
    The ranges need to accommodate all of the expected extremes encountered in the oceans.
    Pressure cannot be less than −5 dbar , Temperature in range −2.5 to 40.0°C , Salinity in range 2 to 41.0 PSU
  • 07

    Regional range test

    This test applies to certain regions of the world where conditions can be further qualified. In this case, specific ranges for observations from the Mediterranean Sea and the Red Sea further restrict what are considered sensible values.
    <Red sea> Temperature in range : 21.7℃~40.0 ℃ , Salinity in range : 2.0psu~ 41.0psu
    <Mediterranean Sea> Temperature in range : 10.0℃~40.0 ℃ , Salinity in range : 2.0psu~ 40.0psu
  • 08

    Pressure increasing test

    This test requires that the profile has pressures that are monotonically increasing
  • 09

    Spike test

    The difference between sequential measurements, where one measurement is significantly different from adjacent ones, is a spike in both size and gradient.
    Test value = | V2 – ( V3 + V1 ) / 2 | - | ( V3 – V1 ) / 2 |
  • 10

    Top and bottom spike test

  • 11

    Gradient test

    This test is failed when the difference between vertically adjacent measurements is too steep.
    Test value = | V2 – ( V3 + V1 ) / 2 |
  • 12

    Digit rollover test

    When the range is exceeded, stored values rollover to the lower end of the range. This rollover should be detected and compensated for when profiles are constructed from the data stream from the float. This test is used to make sure the rollover is properly detected.
  • 13

    Stuck value test

    This test looks for measurements of temperature and salinity in a profile being identical.
  • 14

    Density inversion

    This test compares potential density between valid measurements in a profile, in both directions, i.e. from top to bottom, and from bottom to top.
  • 15

    Grey list

    This test is implemented to stop the real-time distribution on the GTS of measurements from a sensor that is not working correctly.
  • 16

    Gross Sal.or temp. sensor drift

    This test is implemented to detect a sudden and significant sensor drift.
    It calculates the average temperature and salinity from the deepest 100 dbar of a profile and the previous good profile. Only measurements with good QC are used.
  • 17

    Visual QC

    This is subjective visual inspection of float measurements by an operator.
    To avoid delays, this test is not mandatory before real-time distribution.
  • 18

    Frozen profile test

    This test is used to detect a float that reproduces the same profile (with very small deviations) over and over again.