locodox : un outil matlab pour corriger les données argo ... · psat (%) partial pressure of...
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LOCODOX :a matlab toolbox to correct Argo-O2 data
Emilie Brion, Altran OuestVirginie Thierry, LOPS/IfremerCathy Lagadec, LOPS/IFREMER
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Argo Oxygen• Measurements done by
Aanderaa or Seabirdoptodes or other sensor(Rinko)
• 3 useful parameters: Dissolved oxygen
concentration: DOXY (µmol/kg)
Percentage of saturation PSAT (%)
Partial pressure of oxygenPPOX_DOXY (mBar)
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Optode aanderaa
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What is Locodox ?LOCODOX is a matlab toolbox designed to correct oxygen data following 3 methods :
WOA : based on climatological atlas(WOA09 in mL/L)
REF : based on in situ reference profiles collected at float deployment for instance
INAIR : based on in air oxygenmeasurements done by the float
LOCODOX produced delayed mode NetCDF files complying with argo 3.1 format and following the BGC/DOXY QC manuals
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Takeshita et al, 2013Bittig et Kortzinger, 2015
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Exemple of diagnostics
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QC Maps
Interpolation
Drift Correction
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Data
• DOXY, PTS (sensor pressure and temperatureif they exist, …)
• Pumped and unpumped profiles (near surface): « vertical sampling scheme »
« monoprofile » files
• PPOX, PT (sensor temperature if it exists).• To colocalise with NCEP data:
• Ascent End Time : timing associated withPPOX measurements if we have no othertiming data
• Argos localisation
« trajectory » files
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Methodology• Profiles, Traj• Climatology, InSitu Reference, atmospheric dataREAD
• Hook removal• Select QC 1 et 2QC
• Drift corrected if needed• Reference data interpolated on argo levels and
trackPREPARE
• Correction with WOA, REF or In Air• Compute correction on ascendant profilesCOMPUTE CORRECTION
• Apply to both ascendant and descendant profiles• Apply to both pumped and unpumped profilesAPPLY
• scientific calibration fields and history fieldsupdated (Argo Quality Control Manual for BioGeoChemical Data).
Write NetCDF
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Contrôle Qualité : Hook
Data used and considered for the correction are those witha QC = [1,2]
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Hook removal : Many profiles have a hook on about the first 50m of the ascending profile
LOCODOX proposes to the user to remove this hook by systematicallyapply a flag 4 to the base of the profiles:
If Pmax> 840 => [ QC = 4, data = NaN ] on the deepest 50m of the profile
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Interpolation
WOA Correctioninterpolation of WOA alongthe float path+ interpolation
on argo level
REF Correctioninterpolation of referencedata on levels of the Argo profile to be compared to
the reference profile
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Drift estimates and correctionLOCODOX estimate a temporal drift in comparing the Argo time serie with a reference time serie :
• WOA : WOA2009 interpolated on 5 float levelsbelow 1500db (every 100db)
• INAIR : NCEP data compared to float in air measurements (not coded yet)
LOCODOX suggests to not apply the drift correction if :• The timeserie < 1 year• Less than 10 profiles have a pressure max >
1500m• Drift is very small (less than 1,5 mumol/kg)
=> Operator decides
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Drift estimates and correction
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• Argo vs WOA• About 5 years of
data• Drift : -3,1841
umol/kg
⇒ But no correction is necessary
end
start
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WOA09 or REF correction
• Data from the Primary sampling profile (Vertical SamplingScheme)
• Ascending profilesArgo data
• Interpolation on Argo levelsReference data (WOA or in situ)
• Gradient : dDOXY/dz < 0,2 on argo and reference data• Remove outliers ( « argo – référence > +/- 2,8 std)
Data selection to be used for the regression
• DOXY_ADJUSTED=C1*DOXY + C0• if R2 < 0.8, a constant correction is applied and
DOXY_ADJUSTED=DOXY+C0
Linear regression between entre ARGO profile(s) and reference
profile(s) (WOA09 ou REF)
• Ascending and descending profiles• Primary and all other available profiles Application
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Based on Takeshita et al., 2013
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WOA09 or REF correction
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IN AIR correction
• PO2 NCEP (atmospheric reanalyses)• PO2 Optode acquired when the sensor is in the air:
available in « trajectory » file (PPOX)• PO2 Optode acquired in the water (subsurface) : in
current case, data are taken from the near-surface profile (DOXY converted as PPOX), also available in trajectoryfile
Data
• Takes into account bias due to the occasionalsubmersion of the sensor during the in air data acquisition (c : submersion factor, m : correction)
• PO2(air,obs)=c*pO2(water,obs)+(1-c)/m*pO2(air, ncep)Regression
• 𝒑𝒑𝑶𝑶𝟐𝟐(𝒐𝒐𝒐𝒐𝒐𝒐)𝒄𝒄𝒐𝒐𝒄𝒄𝒄𝒄𝒄𝒄𝒄𝒄𝒄𝒄𝒄𝒄𝒄𝒄 = 𝒎𝒎 × 𝒑𝒑𝑶𝑶𝟐𝟐(𝒐𝒐𝒐𝒐𝒐𝒐)• Application aux données pompées et non pompées• Application aux profils ascendants et descendants
Correction : apply
correction factor m to
the rawdata
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Based on Bittig and Kortzinger, 2015
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IN AIR correction
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PSAT float raw PSAT float corrected PSAT WOA
PO2 float water PO2 float in-air PO2 ncep
PO2 float water corrected PO2 float in-air corrected
m = 1,0026 mBar
R2 = 95%
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Comparison
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Raw data
REF corr data
INAIR corr data
WOA corr data
Profils moyens
Hook
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Output
Monocycle NetCDF files complying with argo format 3.1• Update the « DOXY_adjusted » fields:
DOXY_adjusted, DOXY_adjusted_qc,, DOXY_adjusted_error
• Update metadata according to QC manuals: date_update, data_moded, data_state_indicator, parameter_data_mode, history fields, scientific calibfields
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ConclusionLOCODOX take it easy !• Input : NetCDF argo 3.1 files• 3 methods to correct the data depending on availability
of reference data• Output NetCDF argo 3.1 files, follow last Argo/Bio-Argo
recommendations, files went successfully through the format checker
• Easy to use and available to the community, but …
Warnings !• Still debugging the tool, some minor adjustements and
improvements are necessary• Some files are still in format version < 3.1• IN AIR correction method needs to be finalized; needs
to define storage of PPOX_DOXY and near-surface DOXY data
• REF correction: No tool to update the database with in situ reference profiles
• MATLAB + statistic Toolbox• Development stopped until next year (subcontract)
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Conclusion
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• We used LOCODOX with the floats we deployed in the North-Atlantic
• Note those floats were redecoded according to the last cookbook specifications
• 12 floats are now available on the GDAC with DM corrections. More soon
• We already corrected few bugs in LOCODOX• Still some adjustments to do
• PSAL of 1st profile flagged to 4, PSAL is used in LOCODOX DOXY_ADJUSTED=NaN and DOXY_AJUSTED_QC=1
• Need to manage multiple adjustment• Need to take into account that part of the files might be in
Dmode and the other part in Rmode
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Remarks on the storage of in air measurements / in water data used for the in air adjustment
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LOCODOX needs to know where to get in air and in water measurements for the in air adjustment
For some PROVOR/ARVOR floats, in air data are acquired at the end of the ascending profile (end of the unpumped profile):– The entire profile (PO2 and T) (with in water and in air data) are
stored in PPOX_DOXY in the traj file– In the future the in air measurements + last in water
measurement will be easily identifiable in a dedicated phase and stored in the PPOX data in the traj file
What is done for the other floats ? We need to agree on how to store those data.
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REFERENCES
Takeshita et al, 2013: A climatology-based quality control procedurefor profiling float oxygen data: Qc Procedure for Profiling FloatOxygen, J. Geophys. Res. Oceans, 118, 5640–5650, doi:10.1002/jgrc.20399
Bittig and Kortzinger, 2015: Tackling Oxygen Optode Drift: Near-Surface and In-Air Oxygen Optode Measurements on a Float Provide an Accurate in Situ Reference, JAOT, 32, 1536-1543, doi: 10.1002/jgrc.20399
Argo Quality Control Manual For BioGeoChemical data, sur le site web de l’Argo Data Management (http://www.argodatamgt.org/Documentation)
Argo User’s Manual, sur le site web de l’Argo Data Management (http://www.argodatamgt.org/Documentation)
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