Argo Delayed-Mode Quality Control Workshop (DMQC-4) – 28/09/2009 – Toulouse
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The use of Satellite Altimeter data in Argo quality control
Limitations of the method in terms of pressure and salinity signals to be detected
Stéphanie GuinehutCLS, Space Oceanography Division
Argo Delayed-Mode Quality Control Workshop (DMQC-4) – 28/09/2009 – Toulouse
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Reminder of the method The main idea is to compare co-located :
– Altimeter Sea Level Anomalies (SLA) – and Dynamic Height Anomalies (DHA) from Argo T/S profiles
for each Argo float time series
Method :DHA = DH – Mean-DH / SLA
2 times series co-located in time and spaceSLA : AVISO combined mapsDHA : Argo Coriolis-GDAC data baseDH calculated from T/S profiles using a ref. level at 200, 400, 900, 1200 or 1900
dbar only data with : POSITION_QC = ‘0’, ‘1’, ‘5’, ‘8’
JULD_QC = ‘0’, ‘1’, ‘5’, ‘8’ PRES/TEMP/PSAL_QC = ‘1’ (DATA_MODE=‘R’) PRES_ADJ/TEMP_ADJ/PSAL_ADJ_QC = ‘1’ (DATA_MODE=‘A’/’D’)
Mean-DH : contemporaneous Argo mean dynamic height
Argo Delayed-Mode Quality Control Workshop (DMQC-4) – 28/09/2009 – Toulouse
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Impact of the reference level
Good data
Bad data
- Impact of the salinity drift increases with the ref level
Argo Delayed-Mode Quality Control Workshop (DMQC-4) – 28/09/2009 – Toulouse
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Representative anomalies
Spike Float : 5900155
Bad salinity data at depth
Argo Delayed-Mode Quality Control Workshop (DMQC-4) – 28/09/2009 – Toulouse
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Representative anomalies
Offset
Float : 1900581r : 0.61rms-diff : 2187.00 %mean-diff : 15 cmsamples : 69* statistics on DHA-Real
Salinity offsetVertically averaged correction applied= -0.243 psu
Argo Delayed-Mode Quality Control Workshop (DMQC-4) – 28/09/2009 – Toulouse
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SLA DHA (real-time)
Representative anomalies
Drift Float : 5900963
Evidence of a negative pressure drift
Figure : courtesy of Annie Wong
SP ~ –14 dbar
CYCLE NO ~ 119
SLA-DHA ~ 6 cm
Argo Delayed-Mode Quality Control Workshop (DMQC-4) – 28/09/2009 – Toulouse
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Little geographical variations of the impact Impact with reference level and offset
Limitations of the method in terms of pressure and salinity signals to be detected
Theoretical study using WOA05 fields salinity offset
Impact of a salinity offset of +0.05 psu on a (0-900)dbar DH
-3.41 -3.38 -3.35 -3.31 -3.28 -3.25 cm
Argo Delayed-Mode Quality Control Workshop (DMQC-4) – 28/09/2009 – Toulouse
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Limitations of the method in terms of pressure and salinity signals to be detected
Theoretical study using WOA05 fields pressure offset
Impact of a pressure offset of -10 dbar on a (0-900)dbar DH
-6 -4.9 -3.8 -2.7 -1.6 -0.5 cm
Large geographical variations of the impact + small seasonal variations Impact with offset, small differences with ref level
Argo Delayed-Mode Quality Control Workshop (DMQC-4) – 28/09/2009 – Toulouse
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Limitations of the method in terms of pressure and salinity signals to be detected
Tests on a particular float : WMO 5900963
Simulatedpressure offset of -15 dbar
Simulated pressure offset of +15 dbar
Pressure offset
cycles corr. mean(SLA-DHA)(cm)
rms(SLA-DHA)(cm)
rms(SLA-DHA) % rms(SLA)
corr. rms(SLA-DHA) % rms(SLA) ref
no offset 203 0.91 0.91 2.53 20.8 0.85 28-15 dbar 203 0.90 5.14 5.75 107.4 0.85 28+15 dbar 203 0.91 -3.36 4.12 55.1 0.85 28
Impact of the observed mean SLA-DHA differences Impact of the time series length
SL
A /
DH
A
SL
A -
DH
A
Argo Delayed-Mode Quality Control Workshop (DMQC-4) – 28/09/2009 – Toulouse
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Limitations of the method in terms of pressure and salinity signals to be detected
Observed mean SLA-DHA differences
Large-scale consistent signal Higher values in high variability regions
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 cm
Argo Delayed-Mode Quality Control Workshop (DMQC-4) – 28/09/2009 – Toulouse
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Limitations of the method in terms of pressure and salinity signals to be detected
Limitation of the method :
If 5 cm is considered to be the smallest offset to be detected between SLA and DHA
No much help for small offset/drift - compared to P/T/S analysis …
Reference level (dbar)
Min salinity offset (psu)
200 0.3400 0.17900 0.081200 0.061900 0.04
-50 -30 -25 -20 -15 -10 -5 dbar
Min pressure offset that can be detected – 900 dbar DH
Min salinity offset that can be detected