OTT rate deployment GPOD experiment SMOS vs ARGO comparison QWG10 – ESRIN 4-6 February 2013

1. OTT rate deployment GPOD experiment SMOS vs ARGO comparison QWG10 – ESRIN 4-6 February 2013 Justino Martínez & Carolina Gabarró and BEC team SMOS Barcelona Expert Centre Pg. Marítim de la Barceloneta 37-49, Barcelona SPAIN E-mail: smos-bec@icm.csic.es URL: www.smos-bec.icm.csic.es

2. Motivation of GPOD experiment • After last reprocessing campaign important differences in SSS L3 maps were detected. • DPGS operational • L2 products distributed by DPGS in real-time • High variability in SSS bias • These differences are correlated between ascending and descending • Reprocessed • Last reprocessing campaign from 2010/01/12 to 2011/12/22 • More stable behavior • Reason for the differences? Difficult to conclude, different processing conditions were applied: differentdifferentsameonly 1.5 monthsdifferent

3. Tested zones

4. L2 filtering rules L2 - REPR - DPGS total L1c measures <= 90 ACROSS TRACK FILTER • L2PP CNF - file Max iterations reached > 20 Poor fit quality High retrieval sigma > 5 Values out of range (0 .. 42) … VALID L1C RATE +/- 400 km POOR RETRIEVAL L2PP CNF - file Suspect ICE > 50% Rain > 2 l/h Many Outliers > 20% Galactic noise > 10% #measures < 30 … valid L1c measures less than total L1c measures / 3 POOR GEOPHYSICAL HIGH WIND FILTER 1x1 gridsize 10 daysaverageover retrievedSSS - every 3 days Wind speed > 12 m/s BINNING PROCESS

5. Argo values computation Robust interpolation applied to 7.5 m depth 3 interpolation methods on T and SSS compare cells to study the temporal evolution of • SMOS-ARGO Differencesbetweenthe mean and eachinterpolated T and SSS belowthe 5% 1x1 gridsize 10 daysaverageover Argo SSS - every 3 days BINNING PROCESS

6. Differences DPGS vs reprocessed ASCENDING MEAN(SMOS-ARGO) 122 South Eastern Pacific - OTT GLOBAL 127 Tarfaya • DPGS shows high temporal variations • Oscillations not clear correlated with NIR • Pattern independent of the zone. • Linked to the OTT generation zone? • . 124 South Western Tropical Pacific 131 Southern Ocean

7. Differences DPGS vs reprocessed DESCENDING MEAN(SMOS-ARGO) GLOBAL 122 South Eastern Pacific - OTT Tropics • 126 • Equatorial Oceans 131 Southern Ocean • Correlation: Oscillations take place with the same period in ascending and descending. Maxima at • February/March • May/June • October/November • .

8. Differences DPGS vs reprocessed DESCENDING ASCENDING GLOBAL SUN SUN SUN Descending case: SUN affects OTT generation in Feb/Mar and Oct/Nov Ascending case: SUN effects OTT generation in May/June A fast response in OTT deployment is critical in a rapidly changing environment as when Sun is crossing FOV (in DPGS the OTT is computed using L1C from 1-2 weeks earlier and applied during a month) As reportedbyARGANS: Sun in OTT

9. G-POD study Comparison study focused in the OTT deployment rate. Will increasing the OTT generation rate solve the problem? G-POD Recently reprocessed data using G-POD system from 2011/12/23 to 2012/02/29 differentsamesame

10. G-POD study GLOBAL 60S:60N MEAN(SMOS-ARGO) Descending Ascending Purple line: Reprocessing campaign. It can be compared with G-POD experiment results (red line) Red line: G-POD experiment Very different from DPGS (blue line) At a first glance it seems to improve results but it is necessary to carry out a more accurate study

11. Analysisprocedure • Wedepartfrom 10-day SSS mapscomputedevery 3 days • Our target isto compare temporal stability of G-POD and DPGS • Problem: lownumber of points in our time series • Proposedsolution: howwellfitour series to a straight line? • Proceduretoquantifythedegree of improvement • Compute drift (linear fitting) f(t)=at +b of each time series y(t) (G-POD and DPGS) • We use thenonlinearlast-squaresLevenberg-Marquardtmethodalgorithmtofind linear fitting (a and b) and its error (Da and Db) • Substractdritfto time series • e(t) = y(t) - f(t); De(t) = Dy(t) + Df(t) • Compute a measureabouthowfariseachpoint of thevaluee=0 • Thismeasured can be computedforeachpoint (L3 maps) and compare histograms. Thelowerd, thebestfit

12. Results by zone ASCENDING 2 GLOBAL 1 3 In this case 15-days OTT introduces a clear Improvement Eachpointindicatesthe central date of 10-days L3 maps Horizontal errorbarsincludeeach 10-days period. Vertical errorbarsindicatethe error of the mean.

13. Results by zone ASCENDING Tropics 122 South Eastern Pacific - OTT

14. Results by zone ASCENDING 124 South Western Tropical Pacific • 126 • Equatorial Oceans

15. Results by zone ASCENDING 127 Tarfaya 131 Southern Ocean

16. Results by zone DESCENDING Tropics 122 South Eastern Pacific - OTT

17. Results by zone DESCENDING 124 South Western Tropical Pacific • 126 • Equatorial Oceans

18. Results by zone DESCENDING 127 Tarfaya 131 Southern Ocean

19. Conclusions • A fast response in OTT generation and deployment is critical in a rapidly changing environment as when Sun is crossing the FOV • Two strategies: • Center L1C orbits used for OTT generation in the OTT validity period • Generate OTT more frequently (15 days) • To implement this option it is necessary an automatic method to generate OTT with the same quality as the current method (manual) L2 production should be in delayed mode

21. Differences DPGS vs reprocessed ASCENDING

22. Differences DPGS vs reprocessed ASCENDING

23. Differences DPGS vs reprocessed DESCENDING

24. Differences DPGS vs reprocessed DESCENDING

25. G-POD resultsbyzone ASCENDING

26. G-POD resultsbyzone ASCENDING

27. G-POD resultsbyzone DESCENDING

28. G-POD resultsbyzone DESCENDING

29. G-POD resultsbyzone ASCENDING

30. G-POD resultsbyzone ASCENDING

31. G-POD resultsbyzone DESCENDING

32. G-POD resultsbyzone DESCENDING

33. G-POD resultsbyzone ASCENDING

34. G-POD resultsbyzone ASCENDING

35. G-POD resultsbyzone DESCENDING

36. G-POD resultsbyzone DESCENDING