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OSI-SAF METOP-A PROTOTYPE preliminary results

OSI-SAF METOP-A PROTOTYPE preliminary results. P.LeBorgne, H. Roquet, S. Péré MF/CMS. OUTLINE. OBJECTIVES BT SIMULATIONS? PROTOTYPE RESULTS BT simulations SST calculations DISCUSSION Alternate BT simulation adjustments CONCLUSIONS (as of March 2013!). OBJECTIVES.

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OSI-SAF METOP-A PROTOTYPE preliminary results

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  1. OSI-SAF METOP-A PROTOTYPEpreliminary results P.LeBorgne, H. Roquet, S. Péré MF/CMS

  2. OUTLINE • OBJECTIVES • BT SIMULATIONS? • PROTOTYPE RESULTS • BT simulations • SST calculations • DISCUSSION • Alternate BT simulation adjustments • CONCLUSIONS (as of March 2013!) OSI-SAF workshop, Lannion 5-6 March 2013

  3. OBJECTIVES • METOP-A has shown satisfactory results (since 2007) • …but shows regional biases (see Anne’s talk) • No algorithmic solution (see Sonia’s talk) • Accounting for actual atmospheric absorption is needed • A prototype for processing METOP-A has been built • Specifications for processing METOP-B expected before June! OSI-SAF workshop, Lannion 5-6 March 2013

  4. Simulations must be « exact »: they should produce the same BTs as would be observed, given a surface temperature and atmospheric profiles Simulations? • Accounting for actual atmospheric absorption? • 2 main (BT simulation based) approaches: • OE (Merchant et al 2008,2009,2013) • Bias correction (LeBorgne et al, 2011, Petrenko et al, 2011) • SST= guess + S ai (obsBTi-simBTi) OSI-SAF workshop, Lannion 5-6 March 2013

  5. Adjustment needed Simulations? • Differences (short scales?): • Guess distinct from reality • NWP profiles distinct from reality • Errors (short scales?): • Cloud contaminated observations • Errors (larger scales?): • Unaccurate filter functions/calibration errors • RTM errors • Profile sampling errors OSI-SAF workshop, Lannion 5-6 March 2013

  6. Guess differences (nighttime DW!) OSI-SAF workshop, Lannion 5-6 March 2013

  7. Guess differences (nighttime DW!) OSI-SAF workshop, Lannion 5-6 March 2013

  8. Clouds in ECMWF profiles Model vapor too high Dry atmosphere in reality Model vapor too low Humid halo around clouds Profile differences OSI-SAF workshop, Lannion 5-6 March 2013

  9. BT simulations-observations T108 T120 T37 Routine monitoring: cases where SST has been calculated OSI-SAF workshop, Lannion 5-6 March 2013

  10. BT simulations-observations T108 T120 T37 « cloud free » cases: qual. levels > 3; |simBT108-obsBT108| < 1.5K; wind > 2ms-1 OSI-SAF workshop, Lannion 5-6 March 2013

  11. Mean BT difference (simu-obs) (T108) in March 2012 OSI-SAF workshop, Lannion 5-6 March 2013

  12. Mean water vapour content in March 2012 OSI-SAF workshop, Lannion 5-6 March 2013

  13. BT adjustment • Analytic solution not convincing (?) • Daily adjustment maps have been defined (same approach as for operational geostationary processing) • Built from filtered simulation- observation differences averaged… • over 10 days and 10° (lat lon) • Adjustment filtering conditions: • Solar zenith angle > 110 • |SSTope- guess| < 1K (cloud filtering and major guess errors) • |simuT108-obsT108| < 1.5K (cloud filtering and major profile errors) OSI-SAF workshop, Lannion 5-6 March 2013

  14. BT Adjustment for 10.8 mm on the 1rst of March OSI-SAF workshop, Lannion 5-6 March 2013

  15. BT difference (simu-obs) (T108) in March Mean BT difference (simu-obs) (T108) in March 2012 OSI-SAF workshop, Lannion 5-6 March 2013

  16. BT adjustment (T108) in March Mean BT adjustment (T108) in March 2012 OSI-SAF workshop, Lannion 5-6 March 2013

  17. Mean BT adjusted difference (simu-obs) (T108) in March 2012 OSI-SAF workshop, Lannion 5-6 March 2013

  18. BT simulations-observations T108 T120 T37 « cloud free » cases: qual. levels > 3; |simBT108-obsBT108| < 1.5K; wind > 2ms-1 OSI-SAF workshop, Lannion 5-6 March 2013

  19. BT adjusted simulations-observations T108 T120 T37 OSI-SAF workshop, Lannion 5-6 March 2013

  20. BT simulations conclusions • Good results on the average • Smoothing over 10 days and 10° does not resolve extreme (systematic) values nor small scale differences • Not optimal according to Tomazic: 3 days , 15° OSI-SAF workshop, Lannion 5-6 March 2013

  21. SST CORRECTIONS • SSTope= S ai (obsBTi) + cste • SSTsim= S ai (simBTi) + cste • SST_predicted_error= SSTsim-guess • Correction=- SST_predicted_error • SSTcor= SSTope + correction (LeBorgne et al, 2011) -IMPROVEMENTS?? -Comparison with GUESS (OSTIA) -Validation against buoy measurements OSI-SAF workshop, Lannion 5-6 March 2013

  22. SST corrections: comparison to OSTIA Before After Before After OSI-SAF workshop, Lannion 5-6 March 2013 Nighttime Daytime

  23. Daytime mean observed difference to OSTIA JUNE OSI-SAF workshop, Lannion 5-6 March 2013

  24. Qsol >110°! Daytime mean predicted difference to OSTIA JUNE OSI-SAF workshop, Lannion 5-6 March 2013

  25. Daytime mean observed difference to OSTIA SEPTEMBER OSI-SAF workshop, Lannion 5-6 March 2013

  26. Daytime mean predicted difference to OSTIA SEPTEMBER OSI-SAF workshop, Lannion 5-6 March 2013

  27. Nighttime mean observed difference to OSTIA SEPTEMBER OSI-SAF workshop, Lannion 5-6 March 2013

  28. Nighttime mean predicted difference to OSTIA SEPTEMBER OSI-SAF workshop, Lannion 5-6 March 2013

  29. SST corrections: comparison to buoy measurements (qual 3-4-5) Daytime Nighttime Qual >3; |guess-insitu|< 1.5; obst37 > simu-1.; obst108 > simu-1.5 OSI-SAF workshop, Lannion 5-6 March 2013

  30. SST corrections: comparison to buoy measurements (qual 5) Daytime Nighttime St dev. lower than OSTIA’s Qual >5; |guess-insitu|< 1.5; obst37 > simu-1.; obst108 > simu-1.5 OSI-SAF workshop, Lannion 5-6 March 2013

  31. Operational error vs latitude day night OSI-SAF workshop, Lannion 5-6 March 2013

  32. Corrected error vs latitude day night Northern High Latitudes?? OSI-SAF workshop, Lannion 5-6 March 2013

  33. Prototype: Conclusions • BT adjustments seem to work OK, but… • Adjutment parameters are not optimal (see Tomazic et al, 2013) • Threshold on solar zenith angle masks high latitudes by day • SST corrections work OK. • Global stats are improved • Regional biases are significantly reduced. • What’s going on at northern high latitudes? OSI-SAF workshop, Lannion 5-6 March 2013

  34. A New test • Tomazic’s optimal parameters 3 days x 15° • 3.7 mm adjustment as in proto • 10.8 and 12.0 mm adjustment: qsun > 90 or wind > 4 ms-1 • Applied in December 2011, March, June , September 2012 • Global results identical to the previous ones (no surprise) • Allows studying the northern high latitudes in daytime (June) OSI-SAF workshop, Lannion 5-6 March 2013

  35. No wind filtering OSI-SAF workshop, Lannion 5-6 March 2013

  36. Keeping wind > 6ms-1 OSI-SAF workshop, Lannion 5-6 March 2013

  37. OSI-SAF workshop, Lannion 5-6 March 2013

  38. OSI-SAF workshop, Lannion 5-6 March 2013

  39. Ope+cor OSTIA OSTIA vs wind Lat. > 50 N Daytime results in June 2012 vs latitude Ope JUNE 2012 ONLY OSI-SAF workshop, Lannion 5-6 March 2013

  40. Errors origin in June (latitudes > 50°N) OSTIA too cold (DW or other reasons) -> simulations too cold -> simulations over corrected -> simulated SSTs too large -> excessive (negative) corrections. OSI-SAF workshop, Lannion 5-6 March 2013

  41. Alternate BT adjustments • -1-No adjustment • -2-Constant adjustment • T37: +0.05; T108: +0.10; T120: -0.06 (from global statistics) • -3-Analytic formula adjust=a*S+b*S2+c*sst+d*sst2+e*lat+ f* w*S+g* (w*S)2 +h*1/ w +k* (1/ w)2 +cste, • Constant and analytic coefficients derived on MDB with reinforced cloudiness and DW filtering conditions OSI-SAF workshop, Lannion 5-6 March 2013

  42. Day 40865 Ope Ope+cor OSTIA No BT adjust Constant adjust Analytic adjust. d 0.11 -0.06 -0.04 0.39 -0.01 -0.05 s 0.51 0.46 0.32 0.57 0.54 0.50 Night 31449 d -0.05 -0.08 -0.09 0.13 -0.05 -0.06 s 0.35 0.33 0.31 0.36 0.36 0.35 Alternate BT adjustments: global resultsDec+ March+ June + Sept Analytic adjustment not convincing OSI-SAF workshop, Lannion 5-6 March 2013

  43. Alternate BT adjustments: errors vs lat. Dec+ March+ June + Sept Daytime Ope All 4 months OSI-SAF workshop, Lannion 5-6 March 2013

  44. Alternate BT adjustments: errors vs lat. Dec+ March+ June + Sept Daytime Ope + prototype correction All 4 months OSI-SAF workshop, Lannion 5-6 March 2013

  45. Alternate BT adjustments: errors vs lat. Dec+ March+ June + Sept Daytime Analytic adjustment All 4 months OSI-SAF workshop, Lannion 5-6 March 2013

  46. Alternate BT adjustments: errors vs lat. Dec+ March+ June + Sept Daytime Constant adjustment All 4 months OSI-SAF workshop, Lannion 5-6 March 2013

  47. Summary + conclusions as of March 2013 • A prototype has been run for one year (Dec 2011-Nov 2012) • BT adjustment daily maps (10°, 10 days), no explicit DW masking • Corrected SST results are good (nighttime qual 5 better than OSTIA) • Suspicion of problems at Northern High Latitudes -> New experiment (4 months) • At high lats: BT adjustment overest.-> SST correction overest. -> negative bias • Alternate BT adjustments tested: no better solution ? • More work needed • to understand HL problems (DW effect, OSTIA)?? • to refine analytic adjustment (or combine both approaches?) OSI-SAF workshop, Lannion 5-6 March 2013

  48. Extra slides

  49. METOP sumer daytime errors 2nd quarter 3rd quarter Arctic Atlantic vs Barent Sea ? OSI-SAF workshop, Lannion 5-6 March 2013

  50. June Sept cases 53 106 T108 adjust +0.12 -0.12 T108 new adjust -0.02 -0.15 T120 adjust -0.01 -0.27 T120 new adjust -0.14 -0.28 Results: d(s) -0.24 (0.34) -0.11 (0.35) New results -0.09 (0.33) -0.09 (0.27) Effect of reducing BT corrections • Reducing DW effect to OSTIA: • 30% coverage of the pixel grid • |ope-guess_sst| < 0.5 • wind >7 ms-1 • BT adjustment is reduced • (lesser effect in Sept.) • Results are improved OSI-SAF workshop, Lannion 5-6 March 2013

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