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Level 2 Ocean Salinity QWG #4

Level 2 Ocean Salinity QWG #4. 7-9 March 2011. ARGANS & L2OS ESL. Scientific status. Level 1 fixed cal reprocessing analysis (presentation by J. Tenerelli) Drift (impact of TP7 correction) Sun impact LO decimation study (TN/presentation by J. Font)

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Level 2 Ocean Salinity QWG #4

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  1. Level 2 Ocean Salinity QWG #4 7-9 March 2011 ARGANS & L2OS ESL

  2. Scientific status • Level 1 fixed cal reprocessing analysis (presentation by J. Tenerelli) • Drift (impact of TP7 correction) • Sun impact • LO decimation study (TN/presentation by J. Font) • Radiometric accuracy & sun flags (presentation by X. Yin) • OTT drift and quality analysis • OTT sensitivity study: • impact of galaxy signal, num. snapshots, time window (BEC presentation @ PM#20) • Outliers detection to identify RFI • Upgrading roughness models • Rough 1: foam effect added, change in surface spectrum • Rough 2: going to an empirical roughness correction • Rough 3: improving LUT, going to fully empirical model

  3. L2OS status L2OS 0316 enters its 9th month of processing in DPGS... 8 February 2011 10 January 2011 27 December 2010

  4. L2OS status • 317 history • delivered 22 November 2010; FAT passed 7 December 2010 • January installation delayed (L1OP not available) • new roughness model 3 LUT & OTTs for January calibration delivered early February • management meeting 9 February approves installation 317 • 18-25 February IDEAS reject 317 due to AUX_BULL_B validity period issues (40+ emails) • go-ahead for 317 to be installed in DPGS March... • Issues: • L2OS ESL lose 2+ months pre-reprocessing DPGS data analysis • L2OS processor development/testing for summer delivery still using L1OP 34x • no L1c 35x with correct RFI flags yet! • 500 history?

  5. New roughness 3 LUT SM_TEST_AUX_RGHNS3_20050101T000000_20500101T000000_001_012_8 (19/11/2010)

  6. New roughness 3 LUT SM_TEST_AUX_RGHNS3_20050101T000000_20500101T000000_001_013_8 (21/01/2011)

  7. Outlier detection • Outlier test: • abs((Tbmeas - Tbmodel) - correction) > nsig . sigmaTb • ATBD: • correction = median (Tbmeas - Tbmodel) • DPM & 0317: • correction = median (Tbmeas) – median(Tbmodel)

  8. Outlier detection TN analysis prepared by Claire Henocq, Jean-Luc Vergely & Jacqueline Boutin

  9. Outlier detection TN analysis prepared by Claire Henocq, Jean-Luc Vergely & Jacqueline Boutin No longer considered outliers New outliers

  10. Outlier detection • Number of outliers plotted against longitude (0317), latitude +- 1 degree • total outliers 8477, 1570 grid points

  11. Outlier detection • Number of outliers plotted against longitude (0318), latitude +- 1 degree • total outliers 7802, 1570 grid points

  12. Outlier detection: SSS1 0317 0318 delta (317-318) SM_OPER_MIR_SCSF1C_20100802T153816_20100802T163215_344_001_1

  13. Outlier detection: Dg_num_outliers 0317 0318 delta (317-318) SM_OPER_MIR_SCSF1C_20100802T153816_20100802T163215_344_001_1

  14. L1 & L2 RFI flags • L2 fm_l1c_rfi set if any of L1c flags set: • fml1c_rfi_mitigation • fml1c_rfi_strong • fml1c_rfi_point • L2OS 0317 sets fm_valid = false if fm_l1c_rfi set • Some orbits may have L1 RFI flags set over a wide area, eg SM_TEST_MIR_SCSF1C_20100315T080748_20100315T090119_350_001_0 • So L2OS 0317 will find too few measurements for many grid points, leading to missing salinity retrievals

  15. L1 & L2 RFI flags 0317 0318 few outliers? SM_TEST_MIR_SCSF1C_20100315T080748_20100315T090119_350_001_0

  16. Rain Rate ECMWF rain rate is metres/hour (103 litres per m2 per hour), not mm/hr Max values are typically 0.02-0.03 in storms. AUX_CNFOSD/F sets Tg_max_rainfall = 2, so Fg_sc_rain is never set ECMWF Rain_Rate Fg_sc_rain (Tg_max_rainfall = 0.002)

  17. Presentation by J. Tenerelli: land contamination • Radiometric accuracy & sun flags (presentation by X. Yin) • RFI detection (presentation by P. Spurgeon)

  18. Validation of current DPGS L2OS • Using L3 operationally generated by CP34 • SMOS SSS (10 days L3 product) – WOA2005 SSS (climatology for February)

  19. SMOS SSS (10 days L3 product) – Argo at -7.5 m (same period) Bias 0.26 psu STD 0.81 psu Still a lot to improve!

  20. Towards reprocessing • L2OS upcoming improvements for (May/June) delivery (v500) • RFI detection/mitigation • Fg_ctrl_suspect_RFI (no impact on schema), Dg_num_RFI_outliers (UDP schema change) • switch RFI detection on/off, add threshold(s) to AUX_CNFOSD/F • roughness model & configuration tuning • ICM empirical model without flat sea - analysis and algorithm design: CRR impact assessment N/A • fixed PRs: • outlier detection ATBD/DPM mis-match – detected 1 February • mis-use of L1 RFI flags – detected 27 January • wrong ECMWF rain rate units & Tg_max_rainfall/Fg_sc_rain – detected 4 February • BULL_B validity issues – detected 18 February • On-going studies • errors in ECMWF WS (compared to SSMI) lead to bias in SSS – work continuing • investigate sun/galactic glint models (mismatch with SMOS data)

  21. ECMWF/SSMI WS: example of difference

  22. ECMWF/SSMI WS: Average SSSsmos-SSSargo in classes of 1m/s of WSecmwf-WSssmi WSecmwf-WSssmi (m/s)

  23. Time series & site statistics site monitoring: S. Pacific

  24. Site monitoring: S. Pacific (ascending)

  25. Site monitoring: S. Pacific (descending)

  26. Site monitoring: S. Pacific SSS1/2 correlation

  27. SMOS, ARGO (August 2010)& CLIMATOLOGICAL SSS Colocation +/- 5 days, +/-50km, center swath +/-300km, Ascending orbits

  28. SMOS Model 1 - ARGO SSS (3-31 August 2010; asc orbits) versus wind speed (center of orbit)

  29. OTT/drift analysis • Objective • determine OTT drift & required update frequency • Analyse DPGS L2OS 316 salinity drift in stable South Pacific zone (0-30S) • retrieved salinity with sigma_SSS error • SSS anomaly (retrieved – climatology) • Generate new OTT with 0317 for 0, +1, +2, +4, +7, +13, +28, +43 days • 02/08/2010, 03/08/2010, 04/08/2010, 06/08/2010, 09/08/2010, 15/08/2010, 30/08/2010, 14/09/2010 • Compare DPGS L2OS 0316 SSS drift with new OTT drift • Reprocess reference orbit 02/08/2010 with 0317 & new OTT • plot SSS & anomaly drift

  30. DPGS 0316 drift, Aug-Dec 2010 Selected South Pacific orbits, 0-30S, xswath ±300km, unfiltered, with sigma_SSS

  31. DPGS 0316 43 day drift Selected South Pacific orbits, SSS – climatology, 0-30S, xswath ±300km, unfiltered

  32. OTT drift OTT1 delta for selected South Pacific orbits 0-30S, 03/08/2010 to 29/11/2010

  33. Correlation between OTT & DPGS drift OTT delta versus mean SSS for selected South Pacific orbits 0-30S

  34. Reprocessing ref orbit with new OTT 02082010 orbit reprocessed 0317 with OTT from later dates

  35. OTT/drift analysis discussion • Purpose of OTT: • correct L1c TBs so L2OS can retrieve good quality salinity • secondary role: diagnostic for L1c quality • Issues • Wait for L1OP 350 & 317 in DPGS to analyse OTT correction? • Wait for L1PP 500 & L2OS 500 June 2011 & analyse drift/OTT impact? • Perform analysis on fixed cal reprocessed commissioning data? • Analysis strategies • Routine generation of OTT drift statistics? • UDP SSS anomalies or other metrics (eg time-series statistics, collocation match-ups) • Other? • OTT strategies • One per day/week/month etc (eg mid-week – good for commissioning data) • from a single orbit • average of several orbits – eg one ascending & one descending • abrupt transition between OTTs or smoothed – running average? • One size fits all – single OTT for entire reprocessing?

  36. Algorithm validation • Once new L1 500 and L2OS 500 are implemented in DPGS, we will check: • Effectiveness of OTT strategy • Ascending/descending differences • Land contamination • RFI properly removed • Impact of sun and galactic signals • Performance of new roughness models. Comparison of SMOS to Argo and climatology • Timetable?

  37. Decisions proposed to QWG #4 • Increasing LO calibration frequency • RFI outlier detection at L2OS • Removing sun correction at L1 • Extend L1 SUN_POINT flag to a circle around sun • Flagging suspenders at L1

  38. Remembering SSS requirements • R-4.6.2-004 The accuracy of the ocean salinity data products with a 50 km spatial resolution shall be <= 1.2 PSU.Note: This OS Level-2 accuracy requirement corresponds to :·  snapshot images (100) of one pixel taken during one single pass,·  usage of the narrow swath,·  full spatial coverage,·  ocean temperature of 277 K • G-4.7.2-005 The accuracy of the ocean salinity maps outside coastal areas, after averaging over 200 km x 200 km x 10 days space-time domain, shall be <= 0.1 PSU, after corrections by using vicarious calibration, namely by periodical imaging of one or more well-known reference sources.

  39. On statistics • During 10 minutes 500 SMOS snapshots are acquired • Calibrating LO every 10 min means loosing 5 snapshots, then the error in building an L3 map by averaging L2 products (wrt no calibration) increases by sqrt (500)/sqrt(495) = 1.005 • Calibrating every 2 min, 25 snapshots are lost, the L3 error increases by sqrt(500)/sqrt(475) = 1.026 • Going back to one orbit, the increase of usable snapshots @10 min compared to @2 min implies an error reduction of sqrt(495)/ sqrt(475) = 1.02 • This 2% reduction on the required SSS error means 0.02 psu • We showed that calibrating @2 min instead of @10 min implies an error reduction by 0.2 psu (clean Pacific), 0.5 psu in global average

  40. AOB • NIR 2 week calibration • impact on salinity TBD • ascending/descending? • Monitoring products

  41. Solar flare? SM_OPER_MIR_OSDAP2_20110215T015901_20110215T025302_316_002_1

  42. L1c software error flag 20110302T062507 – 20110302T071906

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