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Stéphanie Guinehut CLS, Space Oceanography Division

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 Guinehut CLS, Space Oceanography Division. Reminder of the method. The main idea is to compare co-located :

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Stéphanie Guinehut CLS, Space Oceanography Division

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  1. The use of Satellite Altimeter data in Argo quality controlLimitations of the method in terms of pressure and salinity signals to be detected Stéphanie Guinehut CLS, Space Oceanography Division

  2. 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 space SLA : AVISO combined maps DHA : Argo Coriolis-GDAC data base DH 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

  3. Impact of the reference level • Good data • Bad data - Impact of the salinity drift increases with the ref level

  4. Representative anomalies • Spike Float : 5900155 • Bad salinity data at depth

  5. Representative anomalies • Offset Float : 1900581 r : 0.61 rms-diff : 2187.00 % mean-diff : 15 cm samples : 69 * statistics on DHA-Real Salinity offset Vertically averaged correction applied= -0.243 psu

  6. Representative anomalies • Drift Float : 5900963 SP ~ –14 dbar SLA-DHA ~ 6 cm Figure : courtesy of Annie Wong CYCLE NO ~ 119 Evidence of a negative pressure drift SLA DHA (real-time)

  7. Limitations of the method in terms of pressure and salinity signals to be detected • Theoretical study using WOA05 fields  salinity offset • Little geographical variations of the impact • Impact with reference level and 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

  8. Limitations of the method in terms of pressure and salinity signals to be detected • Theoretical study using WOA05 fields  pressure offset • Large geographical variations of the impact + small seasonal variations • Impact with offset, small differences with ref level 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

  9. Limitations of the method in terms of pressure and salinity signals to be detected • Tests on a particular float : WMO 5900963 • Impact of the observed mean SLA-DHA differences • Impact of the time series length Simulated pressure offset of -15 dbar SLA / DHA SLA - DHA Simulated pressure offset of +15 dbar

  10. 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

  11. 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 … Min salinity offset that can be detected -50 -30 -25 -20 -15 -10 -5 dbar Min pressure offset that can be detected – 900 dbar DH

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