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QWG-10 ESRIN 4-6 February 2013 Quality control study for SMOS data / Flags analysis C. Gabarró, J. Martínez, E. Olmedo M. Portabella, J. Font and BEC team.

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Presentation on theme: "QWG-10 ESRIN 4-6 February 2013 Quality control study for SMOS data / Flags analysis C. Gabarró, J. Martínez, E. Olmedo M. Portabella, J. Font and BEC team."— Presentation transcript:

1 QWG-10 ESRIN 4-6 February 2013 Quality control study for SMOS data / Flags analysis C. Gabarró, J. Martínez, E. Olmedo M. Portabella, J. Font and BEC team J. Boutin & N. Martin, LOCEAN J.L. Vergely, ACRI-st

2 SMOS-BEC Activities Overview, 12-June-2008, Barcelona SPAIN  Analysis of the best combination of L2 flags on L2 and L3 data quality: focus on the usefulness of Chi2 probability flag and galactic noise flag.  L2 comparison with ARGO floats data by selecting data with:  +/- 50 Km between SMOS & ARGO  +/- 5 days between SMOS & ARGO  L3 SMOS SSS with/without flag sorting compared with in situ optimal interpolation maps (ISAS/IFREMER)  Four different flags combinations have been tested at L2 and L3. The RMS (mean/std) and also number of points are important.  Three periods of time:  February -> low galaxy effect  March 2011 ascending -> large effect of galaxy  August -> large galaxy effect 2 / 10 Flagging combination Cases

3 SMOS-BEC Activities Overview, 12-June-2008, Barcelona SPAIN  Fg_ctrl_chi2_P: main goodness of fit indicator; flag on SSS is raised if the probablility that an anomaly occurs about the fit is >95% or less than 5% (too good fit adjustment)  Fg_ctrl_gal_noise: galactic noise flag; flag on SSS is raised if 10% of Tb along a dwell are discarded from the SSS retrieval (e.g. because they are affected by a scattered galactic noise >4K) = since these Tbs are removed from SSS retrieval, retrieved SSS should remain usable (although noisier)  In L2OS v5 Fg_gal_noise included in the Fg_ctrl_poor_geophysical and Fg_ctrl_chi2_P in Fg_ctrl_poor_retrieval 3 / 10 Tested flags

4 QWG-10 ESRIN 4-6 February 2013 4 / 10 Fg_ctrl_chi2 and Fg_ctrl_chi2_P filters description

5 QWG-10 ESRIN 4-6 February 2013 5 / 10 Fg_ctrl_chi2 and Fg_ctrl_chi2_P filters description

6 QWG-10 ESRIN 4-6 February 2013 6 / 10 Dg_chi2_P_X=GAMMq(Nm/2, Chi 2 *Nm /2) If Tg_chi2_P_min Fg_ctrl_chi2_P=0 => GOOD QUALITY Otherwise Fg_ctrl_chi2_P=1 => BAD QUALITY Sometimes the Chi 2 distribution does not match well with the theoretical one => useful indicator of problems for future studies..... Fg_ctrl_chi2_P filter description Nm=33Nm=97 Nm=137 Comparison of density functions (real->red theoretical->blue): >95% <5% BAD QUALITY GOOD QUALITYGOOD QUALITY GOOD QUALITYGOOD QUALITY GOOD QUALITYGOOD QUALITY >95% <5% BAD QUALITY

7 QWG-10 ESRIN 4-6 February 2013 Fg_ctrl_chi2 & Fg_ctrl_chi2_P 7 / 10 Most of the points filtered out by Fg_ctrl_chi2 are at the edges of the swath (for N<50) % of filtered points marchjunedesember 2011 Fg_ctrl_chi2 17.5816.2427.47 Fg_ctrl_chi2_P 29.5527.9939.13

8 becomes very negative for Chi2P>95% Chi2P>95% QWG10, 4-6 Feb. 2013

9 Std(SSSsmos-SSSargo) Chi2P>95% Chi2P<95% Chi2P<75% Std increases when Chi2P>95% => flag is useful for removing bad retrieval Std larger for 75%<Chi2P<95% =>Chi2_P good indicator of SSS quality Std remains at low values for Chi2P<75% QWG10, 4-6 Feb. 2013

10 Number of SMOS measurements: about 20% with Chi2P>95% Chi2P>95% All Chi2P 75%<Chi2_P<95% QWG10, 4-6 Feb. 2013

11 Galactic noise flag: Qualitative effect on SMOS SSS maps: Application of the flag suppress numerous SSS in latitudinal bands => large noise and missing pixels in these areas (e.g. In Southern hemisphere March 2011, ascending orbits) No obvious SSS bias when removing the flag QWG10, 4-6 Feb. 2013 SMOS SSS March 2011 asc orbits

12 Galactic noise flag: Qualitative effect on SMOS SSS maps: Application of the flag suppress numerous SSS in latitudinal bands => large noise and missing pixels in these areas (e.g. In Southern hemisphere March 2011, ascending orbits) No obvious SSS bias when removing the flag QWG10, 4-6 Feb. 2013 SMOS-ISAS SSS March 2011 asc orbits

13 Quantitative effect of Galactic noise flag on SMOS SSS: comparison with ARGO SSS over global Ocean SSS averaged over +/-5days, +/-50km around ARGO) Flag tested Flag not tested Number of colocations QWG10, 4-6 Feb. 2013

14 Quantitative effect of Galactic noise flag on SMOS SSS: comparison with ARGO SSS (Global Ocean) (SMOS SSS averaged over +/-5days, +/-50km around ARGO) Flag tested Flag not tested Mean difference SSSsmos-SSSargo QWG10, 4-6 Feb. 2013

15 Quantitative effect of Galactic noise flag on SMOS SSS: comparison with ARGO SSS (Global Ocean) (SMOS SSS averaged over +/-5days, +/-50km around ARGO) Flag tested Flag not tested Std difference SSSsmos-SSSargo QWG10, 4-6 Feb. 2013

16 Quantitative effect of Galactic noise flag on SMOS SSS: comparison with ARGO SSS in S. subtropical Pacific (10°S-30°S) (SMOS SSS averaged over +/-5days, +/-50km around ARGO) Flag tested Flag not tested Number of colocations QWG10, 4-6 Feb. 2013

17 Quantitative effect of Galactic noise flag on SMOS SSS: comparison with ARGO SSS in S. subtropical Pacific (10°S-30°S) (SMOS SSS averaged over +/-5days, +/-50km around ARGO) Flag tested Flag not tested Mean difference SSSsmos-SSSargo QWG10, 4-6 Feb. 2013

18 Quantitative effect of Galactic noise flag on SMOS SSS: comparison with ARGO SSS in S. subtropical Pacific (10°S-30°S) (SMOS SSS averaged over +/-5days, +/-50km around ARGO) Flag tested Flag not tested Std difference SSSsmos-SSSargo QWG10, 4-6 Feb. 2013 => We propose to remove Fg_Ctrl_gal_noise from Fg_poor_geophysical

19 QWG-10 ESRIN 4-6 February 2013 The following cases have been analyzed at L2 & L3:  Case 1: NO filtering by anything & Xswath=300km  Case 2: RFI=1, High_wind=1 (>12m/s), Poor_ret=1, Poor_geo=1, Xswath=300km: v5 Ctrl_poor_.. flags filtering  Case 3: RFI=1, High_wind=1, Poor_ret=1, Poor_geo=1 (- gal_noise), Xswath=300km  Case 4: RFI=1, High_wind=1, Poor_ret=1 (-chi2), Poor_geo=1 (- gal_noise ), Xswath=300km 19 / 10 Flagging combination Cases

20 QWG-10 ESRIN 4-6 February 2013 20 / 10 ASC/DES orbits 21-30 August [-60,60] DES ASC number of points decrease for fg_ctrl_gal_noise & not better RMS Same number of points only 300km of swath considered 1: No filter 2: poor_geo +poor_ret 3: poor_ret=1, poor_geo=1 (- gal_noise ) 4: poor_ret=1 (-chi2), poor_geo=1 (- gal_noise ) L2-ARGO Since only 300 Km are considered here GP with CHI2 set are already filtered by CHI2_P. Since only 300 Km are considered here GP with CHI2 set are already filtered by CHI2_P.

21 QWG-10 ESRIN 4-6 February 2013 21 / 10 ASC/DES orbits 21-30 August [-60,60] DES ASC number of points decrease for fg_ctrl_gal_noise -> not better values Same number of points only 300km of swath considered 1: No filter 2: poor_geo +poor_ret 3: poor_ret=1, poor_geo=1 (- gal_noise ) 4: poor_ret=1 (-chi2), poor_geo=1 (- gal_noise ) L2-ARGO mean & STD (L2-ARGO) mean & STD (mean(L2)-ARGO)

22 QWG-10 ESRIN 4-6 February 2013 ASC+DES 21-30 August [-60,60] 22 / 10 1: No filter 2: poor_geo +poor_ret 3: poor_ret=1, poor_geo=1 (- gal_noise ) 4: poor_ret=1 (-chi2), poor_geo=1 (- gal_noise ) ASC+DES mean & STD (L2-ARGO) mean & STD (mean(L2)-ARGO) L2-ARGO

23 QWG-10 ESRIN 4-6 February 2013 23 / 10 ASC/DES orbits 21 Feb-2 Mar [-60,60] ASC DES 1: No filter 2: poor_geo +poor_ret 3: poor_ret=1, poor_geo=1 (- gal_noise ) 4: poor_ret=1 (-chi2), poor_geo=1 (- gal_noise ) L2-ARGO

24 QWG-10 ESRIN 4-6 February 2013 ASC+DES orbits 21 Feb-2 Mar [-60,60] 24 / 10 1: No filter 2: poor_geo +poor_ret 3: poor_ret=1, poor_geo=1 (- gal_noise ) 4: poor_ret=1 (-chi2), poor_geo=1 (- gal_noise ) L2-ARGO ASC+DES Similar results for region [-30,30]

25 QWG-10 ESRIN 4-6 February 2013 ASC/DES orbits August/Feb [-10,10] 25 / 10 DES ASC AugustFebruary NOW pseudo L3 similar BIAS & less STD 1: No filter 2: poor_geo +poor_ret 3: poor_ret=1, poor_geo=1 (- gal_noise ) 4: poor_ret=1 (-chi2), poor_geo=1 (- gal_noise )

26 QWG-10 ESRIN 4-6 February 2013 CONCLUSIONS  Better results are obtained when NOT using Fg_ctrl_gal_noise, both at Level 2 and Level 3 analysis -> this filters out many good points during some periods of time.  We consider flag Fg_ctrl_Chi2 should not be used because is theoretically incorrect (should depend on Nm) and GP with bad retrieved are already filtered by Fg_ctrl_Chi2_P.  Large variability on the L2 SMOS data is observed at high latitudes (-40, -60).  Still some land sea contamination is observed. 26 / 10

27 SMOS-BEC Activities Overview, 12-June-2008, Barcelona SPAIN 27 / 10 mean(L2) – ARGO : Pseudo L3 L2 SMOS data with the same ARGO float measurement are averaged -> pseudo L3 5- 24 june 2011 (reprocessed data) Large variability are high latitudes Land Sea contamination Effect or RFI? STD (SMOS) per ARGO (mean(L2 SSS) – ARGO)

28 Extra slides QWG10, 4-6 Feb. 2013

29 SMOS-BEC Activities Overview, 12-June-2008, Barcelona SPAIN Definition of Fg_ctrl_poor_retrieval & Fg_ctrl_poor_geophysical in v500 If (Fg_ctrl_many_outliers(igp) = = true or Fg_ctrl_sunglint(igp) = = true or Fg_ctrl_moonglint(igp) = = true or Fg_ctrl_gal_noise(igp) = = true or Fg_ctrl_gal_noise_pol(igp) = = true or Fg_ctrl_num_meas_low(igp) = = true or Fg_sc_TEC_gradient(igp) = = true or Fg_sc_suspect_ice(igp) = = true or Fg_sc_rain(igp) = = true ) then Fg_ctrl_poor_geophysical (igp) = true If (Fg_ctrl_retriev_fail(igp) = = true or Fg_ctrl_range(igp) = = true or Fg_ctrl_sigma(igp) = = true or Fg_ctrl_chi2(igp) = = true or Fg_ctrl_chi2_P(igp) = = true or Fg_ctrl_marq(igp) = = true or Fg_ctrl_reach_maxiter(igp) = = true) Then Fg_ctrl_poor_retrieval(igp) = true 29 / 10

30 QWG-10 ESRIN 4-6 February 2013 ASC/DES orbits 21-30 August [-30,30] 30 / 10 1: No filter 2: poor_geo +poor_ret 3: poor_ret=1, poor_geo=1 (- gal_noise ) 4: poor_ret=1 (-chi2), poor_geo=1 (- gal_noise ) ASC DES

31 QWG-10 ESRIN 4-6 February 2013 ASC/DES orbits 21 Feb-2 Mar [-30,30] 31 / 10 DES ASC 1: No filter 2: poor_geo +poor_ret 3: poor_ret=1, poor_geo=1 (- gal_noise ) 4: poor_ret=1 (-chi2), poor_geo=1 (- gal_noise )

32 QWG-10 ESRIN 4-6 February 2013 Analysis on L3 MAPS ON DESCENDING 32 / 10 GALACTIC NOISE FLAG ON Descending & August [-60,60] [-30,30] -0. 50 0.9 0.4 1.0 0.55 L3 Maps 1ºx1º SMOS-ARGO Mean(L3-ARGO) STD(L3-ARGO) -0.15 -0. 50 STD(L3-ARGO) Mean(L3-ARGO) -0.15 Mean STD Best results

33 SMOS-BEC Activities Overview, 12-June-2008, Barcelona SPAIN 33 / 10 Fg_ctrl_chi2 filter description Xi 2 /Nm>1.35 ALL THESE POINTS ARE FILTERED Nm=33 Nm=97 Nm=137 Xi 2 /Nm>1.35 ALL THESE POINTS ARE FILTERED Xi 2 /Nm>1.35 ALL THESE POINTS ARE FILTERED Comparison of distribution functions (real->grey theoretical->green): PORTION OF DISGARDED POINTS IS NOT ALLWAYS THE SAME

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