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UPDATE ON GALACTIC NOISE CORRECTION Joe Tenerelli SMOS Quality Working Group # 9 ESA ESRIN

UPDATE ON GALACTIC NOISE CORRECTION Joe Tenerelli SMOS Quality Working Group # 9 ESA ESRIN 24 October 2012. PLAN. Briefly r eview the problem of scattered galactic radiation. Show impact on retrieved salinity . Review the seasonal dependence of the signal.

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UPDATE ON GALACTIC NOISE CORRECTION Joe Tenerelli SMOS Quality Working Group # 9 ESA ESRIN

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  1. UPDATE ON GALACTIC NOISE CORRECTION Joe Tenerelli SMOS QualityWorking Group #9 ESA ESRIN 24 October 2012

  2. PLAN Brieflyreview the problem of scatteredgalactic radiation. Show impact on retrievedsalinity. Review the seasonaldependence of the signal. Look at the impact of the simple specularreflection solution. Motivatedevelopment of more complicatescatteringmodels. Review the performance and problemswith the pre-launch Kirchhoff scattering model, focusing on descending passes. Introducedevelopment of empirically fit geometricalopticsmodels. Show differencesbetweenmodelsderivedfromascending and descending passes. Compare distributions of SSS biases for the variousmodels as a function of scatteredgalacticbrightness.

  3. Cosmic+Galactic (up to 8 K afterscattering) (Tx+Ty)/2 Faraday rotation atm absorption (trans = 0.995) atm absorption (trans = 0.995) atmemission (2 K) atmemission (2 K) Galactic radiation incident from all directions scattering by rough surface specular (100 K) +rough (10 K) surface emission

  4. (Tx+Ty)/2 bias +1 K SSS bias -2 psu

  5. SEASONAL AND PASS DIRECTION VARIATION

  6. SCATTERING OF GALACTIC RADIATION 5 m/s

  7. SEASONAL AND PASS DIRECTION VARIATION April 2 June 25 Sep 20

  8. SEASONAL AND PASS DIRECTION VARIATION June 25 Sep 20 April 2

  9. IMPACT OF CELESTIAL SKY BRIGHTNESS Averaging the scatteredcelestialskybrightnessalong alias-free portions of dwelllines: No correction for reflectedcelestialsky radiation leads to strongalong-track bands of negative SSS anomalies:

  10. IMPACT OF CELESTIAL SKY BRIGHTNESS No correction for reflectedcelestialsky radiation leads to strongalong-track bands of negative SSS anomalies:

  11. IMPACT OF CELESTIAL SKY BRIGHTNESS No correction for reflectedcelestialsky radiation leads to strongalong-track bands of negative SSS anomalies:

  12. IMPACT OF CELESTIAL SKY BRIGHTNESS No correction for reflectedcelestialsky radiation leads to strongalong-track bands of negative SSS anomalies:

  13. IMPACT OF CELESTIAL SKY BRIGHTNESS Correction assuming a specular surface:

  14. IMPACT OF CELESTIAL SKY BRIGHTNESS Correction assuming a specular surface:

  15. IMPACT OF CELESTIAL SKY BRIGHTNESS The preceding Kirchhoff formulation (using the Kudryavtsevwave spectral model) undercorrects for the celestialsky radiation, leaving a noticablealong-track band of negative SSS bias (or high brightnesstemperaturebias):

  16. IMPACT OF CELESTIAL SKY BRIGHTNESS Initial fix for commissioning phase reprocessingwas to use the ‘least rough’ Kirchhoff solution available, corresponding to a 10-m wind speed of 3 m/s. This significantlyreduced the along-track bands of negative SSS bias, but somenoticablebandingremains:

  17. GEOMETRICAL OPTICS GALACTIC MODEL Take high-frequencylimit of the Kirchhoff approximation for scattering cross sections: Obtain expression in terms of slopeprobability distribution: Assume Gaussianslopeprobability distribution. Then fit the slope variance:

  18. FITTING A GEOMETRICAL OPTICS MODEL TO THE DATA: APPROACH Use reconstructedbrightnesstemperatures over the alias-free field of view Correct for running-averaged OTT. OTT basedupondescending passes in first half of year and ascending passes in second half of year, to avoid large influence of galactic radiation uponOTTs. Removal AF-FoVaveragedbias as derivedfrom time-latitude biasevolution. Subtract model predictedbrightnesstemperature, excluding contribution fromcelestialskybrightness. Project resulting ‘residual’ brightnesstemperaturesinto a regular 1ox1ogrid in celestialcoordinates. Use all data fromJune 2010-July 2012. Fit model on ascending and descending passes separately.

  19. FITTING A GEOMETRICAL OPTICS MODEL TO THE DATA: ASCENDING PASSES SMOS residuals Examplegeometricaloptics trial solutions

  20. FITTING A GEOMETRICAL OPTICS MODEL TO THE DATA: ASCENDING PASSES SMOS residuals Examplegeometricaloptics trial solutions

  21. FITTING A GEOMETRICAL OPTICS MODEL TO THE DATA: ASCENDING PASSES

  22. FITTING A GEOMETRICAL OPTICS MODEL TO THE DATA: ASCENDING PASSES

  23. IMPACT OF CELESTIAL SKY BRIGHTNESS Reflected radiation for ascending passes in March not as strong as for descending passes in Sep/Oct:

  24. IMPACT OF CELESTIAL SKY BRIGHTNESS Scattered radiation for ascending passes in March also not as strong as that for descending passes in Sep/Oct:

  25. IMPACT OF CELESTIAL SKY BRIGHTNESS

  26. IMPACT OF CELESTIAL SKY BRIGHTNESS

  27. FITTING A GEOMETRICAL OPTICS MODEL TO THE DATA: DESCENDING PASSES SMOS residuals Examplegeometricaloptics trial solutions

  28. FITTING A GEOMETRICAL OPTICS MODEL TO THE DATA: DESCENDING PASSES SMOS residuals Examplegeometricaloptics trial solutions

  29. FITTING A GEOMETRICAL OPTICS MODEL TO THE DATA: DESCENDING PASSES

  30. FITTING A GEOMETRICAL OPTICS MODEL TO THE DATA: DESCENDING PASSES

  31. FITTING A GEOMETRICAL OPTICS MODEL TO THE DATA: DESCENDING PASSES

  32. COMPARING THE ASC AND DESC MSS FITS • At high incidence angles, optimal mean square slopes for descending passes are lowerthanthose for ascending passes. Discrepancyislargestat 50o incidence angle (where the GO fit ismostproblematic). • Atlow incidence angles, the opposite istrue. • Change occurssomewherebetween 20o and 40o incidence angle.

  33. AN EXAMPLE OF THE FIT 40o incidence angle Descending passes 6-8 m/s ECMWF surface wind speed first Stokes parameter: (Tx+Ty)/2

  34. FITTING A GEOMETRICAL OPTICS MODEL TO THE DATA: DESCENDING PASSES Descending SMOS

  35. FITTING A GEOMETRICAL OPTICS MODEL TO THE DATA: DESCENDING PASSES Descendinggeometricaloptics model

  36. FITTING A GEOMETRICAL OPTICS MODEL TO THE DATA: DESCENDING PASSES Descendinggeometricaloptics model

  37. FITTING A GEOMETRICAL OPTICS MODEL TO THE DATA: DESCENDING PASSES Kirchhoff model at 3 m/s

  38. LOWER SURFACE WIND SPEED 40o incidence angle Descending passes 3-6 m/s ECMWF surface wind speed first Stokes parameter: (Tx+Ty)/2

  39. LOWER SURFACE WIND SPEED Descendinggeometricaloptics model

  40. LOWER SURFACE WIND SPEED Kirchhoff model at 3 m/s Kirchhoff model at 3 m/s underpredictsscatteredbrightnessalonggalactic plane and overpredictsit on eitherside.

  41. COMPARING ASCENDING AND DESCENDING GEOMETRICAL OPTICS MODEL FITS 40o incidence angle Descending passes 3-6 m/s ECMWF surface wind speed first Stokes parameter: (Tx+Ty)/2

  42. COMPARING ASC AND DESC GO MODELS DescendingEmpirical GO model – SMOS derived (Tx+Ty)/2:

  43. COMPARING ASC AND DESC GO MODELS AscendingEmpirical GO model – SMOS derived (Tx+Ty)/2: Ascendingempirical GO model underpredictsscatteredcelestialskybrightnessalong the galactic plane and overpredictsit on eitherside:

  44. COMPARING ASC AND DESC GO MODELS Descending - AscendingEmpirical GO model Descendingpassempirical GO model predicts A more sharplypeaked distribution of scatteredcelestialsky noise:

  45. ORIENTATION ANGLE DEPENDENCE A possible explanation for descending-ascendingdifferences in scatteredgalactic radiation for a givenspecular point… galacticbrightness scattering cross sections surface

  46. ORIENTATION ANGLE DEPENDENCE The brightness incident atantenna for anygivenspecular point dependsupon orientation of the incidence plane. Modelspredictthis and the data alsosuggestsuch a dependence.

  47. IMPACT OF THE ORIENTATION ANGLE

  48. SPECULAR REFLECTION OF THE GALAXY AT VERY LOW ECMWF 10 METER WIND SPEEDS

  49. IMPACT OF CELESTIAL SKY BRIGHTNESS In some cases itappearsthat the galactic radiation isspecularlyreflectedat ECMWF surface wind speeds below 2-3 m/s. But thisis not always the case:

  50. IMPACT OF CELESTIAL SKY BRIGHTNESS Green circles: evidence of specularreflection of galactic radiation

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