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EXTENDING THE LAND SEA CONTAMINATION CHARACTERIZATION TO THE EXTENDED ALIAS-FREE FIELD OF VIEW

EXTENDING THE LAND SEA CONTAMINATION CHARACTERIZATION TO THE EXTENDED ALIAS-FREE FIELD OF VIEW Joe Tenerelli (CLS) and Nicolas Reul (IFREMER) SMOS Quality Working Group #15 ESA ESRIN 6-8 October 2014. REMINDER OF THE PROBLEM.

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EXTENDING THE LAND SEA CONTAMINATION CHARACTERIZATION TO THE EXTENDED ALIAS-FREE FIELD OF VIEW

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  1. EXTENDING THE LAND SEA CONTAMINATION CHARACTERIZATION TO THE EXTENDED ALIAS-FREE FIELD OF VIEW Joe Tenerelli (CLS) and Nicolas Reul (IFREMER) SMOS Quality Working Group #15 ESA ESRIN 6-8 October 2014

  2. REMINDER OF THE PROBLEM There is a significantbiasin the retrievedsurface salinityaround all of the continents, and thisbiasseems to bestable over the entiremission. By significant I meanthat the biasescanexceed 2 pss, while the range of SSS over the global oceansis 30-40 pss (awayfrom river plumes and freshwaterlenses). Wewill call thisbias land-sea contamination, or LSC.

  3. AN EXAMPLE OF LSC AROUND AUSTRALIA BASED UPON ARGO MEASUREMENTS FROM 2010-2013

  4. AN EXAMPLE OF LSC AROUND SOUTH AMERICA BASED UPON ARGO MEASUREMENTS FROM 2010-2013

  5. GLOBAL LSC IN TERMS OF FIRST STOKES PARAMETER The LSC is global: ASCENDING PASSES FOR MAY 2011: FIRST STOKES PARAMETER BIAS

  6. GLOBAL LSC IN TERMS OF RETRIEVED SALINITY The LSC is global: ASCENDING PASSES FOR MAY 2011: RETIEVED SALINITY BIAS

  7. GLOBAL LSC IN TERMS OF RETRIEVED SALINITY Note: In thispresentation SMOS SSS isretrievedusing the first Stokes parameterand a simple linearretrievalalgorithm. ASCENDING PASSES FOR MAY 2011: RETIEVED SALINITY BIAS

  8. LSC IS SCENE-DEPENDENT The biases are alsoscene-dependentand thereforechange as the distribution of land over the front halfspace changes:

  9. THE LSC CORRECTION Given the preceding, we suppose that the ‘land contamination’ bias in polarization p maybeexpressed as whereis the pass direction, are the geographic longitude and latitude and are the usualdirectorcosinecoordinates. As a first test wedeveloped a coarselookup table over just the alias-free field of view (AF-FOV). Hereweextend the results to the extended alias-free field of view (EAF-FOV). ∆Tp(D,λg,θg,ξ,η),

  10. KEY POINTS OF THE EMPIRICAL LSC CORRECTION • latitude-longitude grid: 0.5x0.5 deglat-longrid • Directorcosinegrid: 0.025x0.025 directorcosineunitsratherthan 0.1x0.1 directorcosineunits • Twolookup tables are calculated: One for RFI-flaggedsnapshots and another for non-RFI-flagged (nominal) snapshots. • 41,469 half-orbits are used to compute the mission average land contamination. • Biases in all four Stokes parameters are computed. • Final correction isweighted by a functionthatapproacheszero as the fraction of land in the front halfspaceapproaches 0.2% and approaches one as the fraction approaches 1%. • The correction alsoapproacheszero as the ice fraction approached 0.02%.

  11. DISCRETIZATION

  12. PROCESSING STEPS (1) Accumulate data intodailymaps on 0.5°x0.5° lat-longrid; removegridpointswith no measurements; introducelinearindexing for retainedgridpoints Successive snapshots (‘scene’) (Tx,Ty,Uxy,Vxy) on hexgrid Flag scene for RFI: Tx > 500 K or Ty > 500 K or Uxy > 200 K Accumulate data intomonthlymaps; keeptrack of pointwisemeasurementcounts Computebias relative to forward model (ref. SSS is WOA-2009) for all four Stokes parameters in instrument polarization basis Createseparatemonthly files for each variable RFI-free RFI-flagged Average the monthly Stokes parameterbiasmaps over the full period(Jan 2010-June 2014) Gridbiases onto ISEA-4H9 grid and identify (xi,eta) bins

  13. PROCESSING STEPS (2) Applysimilarweightingfunctionthatramps to 0 as the ice fraction approaches 0.02%. Removegridpointswithfewerthan 10 passes enteringinto the average Set correction to zerosouth of 60°S latitude For each (xi,eta) cell, removeaveragebias over all (lat,lon) cellswith no land or ice in the front half-space; removes impact of the choice of OTT Merge all Stokes parameterbiases (single precision) into a single file for eachpass direction and for RFI and non-RFI-flaggedscenes. Each file is 2.45 GB in size with about 88 million gridpoints in each. Applylinearweightingfunction to biaseswhichramps down from 1 at FHS land fraction of 1% to 0 at land fraction of 0.2%.

  14. DISCRETIZATION

  15. EXAMPLE BIAS OVER EAF-FOV

  16. MEASUREMENT COUNT FOR THE AVERAGING non-RFI-flaggedsnapshots

  17. EXAMPLE MAP OF THE FIRST STOKES BIAS non-RFI-flaggedsnapshots

  18. MEASUREMENT COUNTS FOR THE AVERAGING RFI-flaggedsnapshots

  19. EXAMPLE MAP OF THE FIRST STOKES BIAS RFI-flaggedsnapshots

  20. EVALUATION OF THE CORRECTION Global perspective for May 2011 Impact in areas with stable SSS: Australia and South America in May 2011 using ISAS as the reference Comparisonwith ARGO data aroundAustralia and South America over the period 2010-2013 Impact in areas withstronglyvarying SSS: Panama and the Amazon plume regions

  21. EVALUATION OF THE CORRECTION Global perspective for May 2011 Impact in areas with stable SSS: Australia and South America in May 2011 using ISAS as the reference Comparisonwith ARGO data aroundAustralia and South America over the period 2010-2013 Impact in areas withstronglyvarying SSS: Panama and the Amazon plume regions

  22. INITIAL EVALUATION OF THE CORRECTION USING THE MONTH OF MAY 2011 AND THE ISAS MONTHLY MAP FIRST STOKES PARAMETER DIVIDED BY TWO BEFORE CORRECTION

  23. INITIAL EVALUATION OF THE CORRECTION USING THE MONTH OF MAY 2011 AND THE ISAS MONTHLY MAP FIRST STOKES PARAMETER DIVIDED BY TWO AFTER CORRECTION

  24. INITIAL EVALUATION OF THE CORRECTION USING THE MONTH OF MAY 2011 AND THE ISAS MONTHLY MAP DESCENDING-ASCENDING BIAS BEFORE CORRECTION

  25. INITIAL EVALUATION OF THE CORRECTION USING THE MONTH OF MAY 2011 AND THE ISAS MONTHLY MAP DESCENDING-ASCENDING BIAS AFTER CORRECTION

  26. EVALUATION OF THE CORRECTION Global perspective for May 2011 Impact in areas with stable SSS: Australia and South America in May 2011 using ISAS as the reference Comparisonwith ARGO data aroundAustralia and South America over the period 2010-2013 Impact in areas withstronglyvarying SSS: Panama and the Amazon plume regions

  27. INITIAL EVALUATION OF THE CORRECTION USING THE MONTH OF MAY 2011 AND THE ISAS MAPS First considertwo areas with stable surface salinitywhose distribution iswell-measured by ARGO floats.

  28. INITIAL EVALUATION OF THE CORRECTION USING THE MONTH OF MAY 2011 AND THE ISAS MAPS First considertwo areas with stable surface salinitywhose distribution iswell-measured by ARGO floats.

  29. INITIAL EVALUATION OF THE CORRECTION USING THE MONTH OF MAY 2011 AND THE ISAS MAPS First considertwo areas with stable surface salinitywhose distribution iswell-measured by ARGO floats.

  30. INITIAL EVALUATION OF THE CORRECTION USING THE MONTH OF MAY 2011 AND THE ISAS MAPS

  31. INITIAL EVALUATION OF THE CORRECTION USING THE MONTH OF MAY 2011 AND THE ISAS MAPS CORRECTION REDUCES VARIATION OF BIAS WITH LAND FRACTION OUTSIDE THE FUNDAMENTAL HEXAGON

  32. INITIAL EVALUATION OF THE CORRECTION USING THE MONTH OF MAY 2011 AND THE ISAS MAPS CORRECTION REDUCES VARIATION OF BIAS WITH LAND FRACTION OUTSIDE THE FUNDAMENTAL HEXAGON

  33. INITIAL EVALUATION OF THE CORRECTION USING THE MONTH OF MAY 2011 AND THE ISAS MAPS

  34. INITIAL EVALUATION OF THE CORRECTION USING THE MONTH OF MAY 2011 AND THE ISAS MAPS BIAS APPEARS AS SOON AS LAND APPEARS OUTSIDE THE FUNDAMENTAL HEXAGON

  35. INITIAL EVALUATION OF THE CORRECTION USING THE MONTH OF MAY 2011 AND THE ISAS MAPS BIAS APPROACHES 2.5 PSU AS THE LAND FRACTION APPROACHES 0.9.

  36. INITIAL EVALUATION OF THE CORRECTION USING THE MONTH OF MAY 2011 AND THE ISAS MAPS

  37. INITIAL EVALUATION OF THE CORRECTION USING THE MONTH OF MAY 2011 AND THE ISAS MAPS

  38. INITIAL EVALUATION OF THE CORRECTION USING THE MONTH OF MAY 2011 AND THE ISAS MAPS CORRECTION SEEMS TO REDUCE THE ABSOLUTE ERROR TO ABOUT 150-200 KM FROM THE COAST. CORRECTION IS LESS EFFECTIVE WITHIN 150 KM OF THE COAST.

  39. EVALUATION OF THE CORRECTION Global perspective for May 2011 Impact in areas with stable SSS: Australia and South America in May 2011 using ISAS as the reference Comparisonwith ARGO data aroundAustralia and South America over the period 2010-2013 Impact in areas withstronglyvarying SSS: Panama and the Amazon plume regions

  40. ARGO COLLOCATIONS: AUSTRALIA

  41. ARGO COLLOCATIONS: AUSTRALIA ARGO-SMOS collocations are binnedinto 50 km wide bands (as a function of distance to coast). Biases are thencomputed in these bands. TIME PERIOD: 2010-2013

  42. ARGO COLLOCATIONS: AUSTRALIA UNCORRECTED SMOS SSS

  43. ARGO COLLOCATIONS: AUSTRALIA CORRECTED SMOS SSS

  44. ARGO COLLOCATIONS: AUSTRALIA

  45. ARGO COLLOCATIONS: AUSTRALIA biasreduction of about 0.5 pss

  46. ARGO COLLOCATIONS: AUSTRALIA Impact of the LSC correction drops rapidlywithin about 200 km of the coast

  47. ARGO COLLOCATIONS: AUSTRALIA biasreduction of about 0.8 pss

  48. A COMPARISON WITH SHIP TSG DATA WITHOUT LSC CORRECTION

  49. A COMPARISON WITH SHIP TSG DATA WITH LSC CORRECTION

  50. ARGO COLLOCATIONS: SOUTH AMERICA

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