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On SMOS SSS biases in 2012 ... SMOS – In situ comparisons in SPURS region

On SMOS SSS biases in 2012 ... SMOS – In situ comparisons in SPURS region. J. Boutin*, N. Martin*, O. Hernandez*, G. Reverdin* *LOCEAN. Mean SSS in OTT region (2012: real time SSS; OTT not well phased). 2012. What differences between:

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On SMOS SSS biases in 2012 ... SMOS – In situ comparisons in SPURS region

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  1. On SMOS SSS biases in 2012 ... SMOS – In situ comparisons in SPURS region J. Boutin*, N. Martin*, O. Hernandez*, G. Reverdin* *LOCEAN

  2. Mean SSS in OTT region(2012: real time SSS; OTT not well phased) 2012 • What differences between: • using a bias correction method based on observed SSS biases in the ‘OTT region’ wrt to updating OTT • using WOA climatology as reference or ISAS (interpolated in situ measurements) and using whole ‘OTT area’ (45°S-5°S) or a reduced area (30°S-5°S) N. Martin e al. 2012

  3. Mean SSS in OTT region(2012: real time SSS; OTT not well phased) 2012 Before the catch-up reprocessing, we test an adhoc correction (OCOR): For each point in the OTT area (140W-95W; 45S-55S): DSSS=SSSsmos-SSSwoa => DTb(DSSS, SSS, SST, WS) => <DTb>ott In each ocean pixel: DSSS=f(<DTb>ott, SSS, SST, WS)

  4. Adhoc correction (OCOR): For each point in the OTT area (140W-95W; 45S-55S): DSSS=SSSsmos-SSSwoa => DTb(DSSS, SSS, SST, WS) => <DTb>ott In each ocean pixel: DSSS=f(<DTb>ott, SSS, SST, WS) Daily<DTb>ott Ascending orbits 5 day running mean of <DTb>ott Ascending orbits WOA, 5S-45S ISAS, 5S-45S WOA, 5S-30S ISAS, 5S-30S Various curves using WOA SSS or ISAS SSS, 5S-30S or 5S-45S as reference => weak differences (<0.1K but not completely negligible) Daily<DTb>ott very noisy => we use 5day running means computed on ascending and descending orbits separetly and using WOA as reference

  5. Adhoc correction (OCOR): For each point in the OTT area (140W-95W; 45S-55S): DSSS=SSSsmos-SSSwoa => DTb(DSSS, SSS, SST, WS) => <DTb>ott In each ocean pixel: DSSS=f(<DTb>ott, SSS, SST, WS) Daily<DTb>ott Descending orbits 5 day running mean of <DTb>ott Descending orbits WOA, 5S-45S ISAS, 5S-45S WOA, 5S-30S ISAS, 5S-30S Various curves using WOA SSS or ISAS SSS, 5S-30S or 5S-45S as reference Daily<DTb>ott very noisy => we use 5day running means computed on ascending and descending orbits separetly and using WOA as refernce

  6. BIASES on monthly SSS maps with respect to ISAS SSS Ascending orbits Descending orbits REPR-ISAS WOA-ISAS OTT Area 45°N- 45°S OCOR-ISAS Less variable biases with OCOR than with REPR because of daily correction ‘Global’ biases very different from biases in OTT region!!

  7. Different biases in OTT region and other regions......

  8. STD of (SMOSOCOR SSS - SMOSREPR SSS) Ascending orbits Descending orbits 45°N- 45°S The temporal variation of biases within 15days + the variation of the biases in the FOV => std >0.1 on monthly 1° maps!!! Almost no difference between applying a mean daily bias (OCOR_1day) or a 5 days running mean (OCOR_5days)

  9. STD of (SMOS SSS - ISAS SSS) for OCOR and OTT_Repr corrections Ascending orbits Descending orbits OTT Area 45°N- 45°S Although OTT_REPR correction is not daily, std (SMOS-ISAS) is equivalent (or even smaller) for REPR than for OCOR => a mean correction is less efficient than a varying OTT correction (at least with uncorrect galactic map!)

  10. October 2012 Desc. OCOR-ISAS REPR-ISAS Over 45S-45N : OCOR-ISAS : -0.17 (std=0.47) REPR-ISAS : 0.28 (std=0.45)

  11. Summary A correction deduced from mean SSS bias over ‘OTT area’ corrects a large part of biases but remains less efficient than updating OTT Needs for updating OTT more frequently than every 2 weeks will improve But Large north-south biases remain In ‘OTT region’ : North-south variations of biases and SSS variations wrt climatology responsible for uncertainty in OTT <0.1K

  12. SPURS area

  13. Large scale bias between SMOS & AQUARIUS averaged over SPURS area We first correct for a mean bias between SMOS & WOA or AQUARIUS & WOA

  14. Comparisons SMOS-Toucan & Colibri (+/-9jours, +/-50km) Mean and standard deviation of SSS SMOS – SSS TSG for each campaign (Colibri and Toucan). Correction of bias B1 is applied. In green: colocalisations in October 2011 Mean negative bias because WOA SSS often lower than in situ SSS

  15. SSS in October 2011 in SPURS region SMOS SSS theoretical error

  16. SSS in October 2011 in SPURS region

  17. SSS in August 2012 during the STRASSE campaign

  18. Boutin et al., AGU 2012

  19. Summary of SPURS comparisons Once large scale seasonal bias has been corrected, rms error of SMOS SSS ~0.2; SMOS allows a good monitoring of SSS spatial structures at 50-100km scale

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