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Enhancements and Verifications in Ocean Salinity Retrievals: L2OS Processing Updates

This document outlines recent updates and verifications in the Level 2 Ocean Salinity (L2OS) processing from September 2010. It discusses various actions taken to improve retrieval quality, including adjustments to outlier detection thresholds, improved model performance for wind speed, and ongoing product verification processes. Notably, the impacts of land contamination and instrument drift on salinity retrievals are also examined, alongside recommendations for new analysis techniques. The analysis highlights collaboration among organizations, ongoing issues, and future needs for refining empirical models.

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Enhancements and Verifications in Ocean Salinity Retrievals: L2OS Processing Updates

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  1. Level 2 Ocean Salinity QWG #2 13-14 September 2010 ARGANS & L2OS ESL

  2. L2OS DPGS retrievals CPU reset L1OP 330 L1OP 342 L1OS 314 OTTs December March June

  3. L2OS DPGS retrievals L1OP 344 & L2OS 316 December March June August

  4. L2OS DPGS good quality retrievals

  5. L2OS 0315 – L1OP 342 05/07/2010 L2OS 0315 – wrong OTT

  6. L2OS 0316 – L1OP 344 06/07/2010 L2OS 0316 & new OTTs using L1PP 340

  7. L2OS 0316 – L1OP 344 09/07/2010 L2OS 0316 & new OTTs using L1OP 344

  8. L2OS 0316 – L1OP 344 02/08/2010 L2OS 0316 & new OTTs using L1PP 340 with new FTR

  9. L2OS status • OTTs made from L1PP verified with L1OP (TN available) • Faraday rotation verified • Product verification ongoing • Configuration & tuning • Improved outlier detection threshold • Model 1 performs better retrieving wind speed instead of wind vectors • Testing AFFOV only or limited xi/eta • L1c full pol Stokes 3 & forward model mismatch – better to process dual from full? • Retrieval quality criteria need evaluation/refining • Empirical model needs tuning • Land contamination still an issue • Drift in retrieved salinity – instrument?

  10. Salinity drift 5 day average SSS2 9-13 July 2010

  11. Salinity drift 5 day average SSS2 28 July – 1 August 2010

  12. Salinity drift 5 day average SSS2 3-7 August 2010

  13. Salinity drift 5 day average SSS2 30 August – 3 September 2010

  14. Activity: OTT verification – L1PP/OP • Action: ARGANS • Status: verified (see TN) – difference between OP/PP same as between ascending/descending & models

  15. Activity: Faraday rotation angles & sign • Action: ARGANS • Status: L2OS 0316 verified with L1OP & L1PP • angles match L1OP 344 & L1PP exactly SM_OPER_MIR_SCSF1C_20100802T153816_20100802T163215_344_001_1

  16. Activity: attitude computation: xi/eta • Action: ARGANS • Issue: L2OS performs attitude computation with EECFI instead of using L1 angles, because xi/eta needed for applying OTTs in antenna frame • ESA TN from Montse version v3.4 (& 3.3) computes off-nadir angle using flat earth assumption – giving large errors. • Recommend new TN with spherical earth & mini-TDS for verification? • L2OS will use L1 angles & no longer need BFP/MISP/EECFI • all angles will be target to satellite

  17. Activity: Gibbs 2 & 3 analysis • Action: ACRI, LOCEAN • Status: • Joe analysed Gibbs 2, couldn’t make any sense of the data • TN available from Claire Henocq, SEPS-GS, dual pol only • Should be considered at L1, together with land contamination (& earth-sky) • L2OS will look at results when Gibbs 2/3 is known to be working

  18. Activity: OTT sensitivity/bias correction • Action: ICM, ACRI • OTT not stable – varies with latitude &/or land proximity (Jean-Luc’s TN) • Also see BEC’s presentation – analysis continuing

  19. Activity: Sensitivity of LO calibration frequency • Action: ICM • Status: waiting for improvements in retrieval quality before analysis • Requirements: • “controlled” drift situation • One month of full pol data acquired with LO calibrated every 6 min • Draft analysis plan (comparing two consecutive months, 10 + 6 min): • Tb statistics • SSS statistics • Number of retrievals • ...

  20. Activity: Full pol analysis comparing Stokes 3 & 4 with L1c • Action: ARGANS • Status: need 3rd Stokes correction in L1 or forward model (TBD)? • LOCEAN sent comparison to Raffaele showing L1OP not working (L1PP ok) • ARGANS & CLS: L1c & forward model Stokes 3 & 4 mismatch

  21. Activity: analysis of TEC accuracy/retrieval • Action: ARGANS • Status: ongoing Before correcting L2OS Faraday rotation angle (left); after (right)

  22. Activity: RFI Fiji RFI DPGS orbit: Dg_chi2_1 (left), Dg_chi2_P_1 (right)

  23. Activity: RFI Dg_num_outliers along swath – double peaks around N. New Zealand & Fiji

  24. Activity: RFI RFI uncorrected (left), corrected (right) full pol Fiji orbit: full from full

  25. Activity: RFI RFI uncorrected (left), corrected (right) full pol Fiji orbit: dual from full

  26. Activity: Semi-empirical roughness model improvement • Action: ICM • Status: • No updated parameters yet to be included in L2OS processor • Ongoing study (methodology prepared, first tests) • Need many orbits to have significant statistical analysis • Need a good filtering of the data, as well as the best possible OTT • More details by C. Gabarró on Wednesday

  27. Activity: stripping • Increase threshold for valid number of measurements Tg_num_meas_valid 16 (left), 30 (centre), 50 (right)

  28. Algorithm Improvements • Retrieve SSS1 using WS, not vectors • Add RFI support • use L1 flags & AUX_DGGRFI • detect at L2 • write L2 flags for users, analysis, & AUX_DGGRFI • OTT strategy • TEC

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