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Reanalysis and climate monitoring

Reanalysis and climate monitoring. Lennart Bengtsson Environmental System Science Centre University of Reading, UK. Thanks to ECMWF Uppala and Simmons. Reanalysis and climate monitoring. Achievements Challenges Vision. Reanalysis. Why reanalysis? Background What has been achieved

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Reanalysis and climate monitoring

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  1. Reanalysis and climate monitoring Lennart Bengtsson Environmental System Science Centre University of Reading, UK Thanks to ECMWF Uppala and Simmons Reanalysis and climate monitoring Lennart Bengtsson

  2. Reanalysis and climate monitoring • Achievements • Challenges • Vision Reanalysis and climate monitoring Lennart Bengtsson

  3. Reanalysis • Why reanalysis? • Background • What has been achieved • Limitations Reanalysis and climate monitoring Lennart Bengtsson

  4. Why reanalysis? • It is required to integrate different kind of observations in a consistent way making it possible to project the observation on suitable scales of motion. • Such an approach is needed for a systematic control of observational quality. • Many studies require access to data in gridded form. • This include diagnostic and predictive studies needed for an integrated assessment of observational data. Reanalysis and climate monitoring Lennart Bengtsson

  5. Examples of re-analyses • FGGE-1 ( ECMWF and GFDL) 1979 • ERA-15 (ECMWF) 1990 • ERA-40 (ECMWF) 2001 • NCAR/NCEP- ( US Org.) 1988 • JMA - 25 ( Japan Met Agency) 2005 Reanalysis and climate monitoring Lennart Bengtsson

  6. How can we measure the value (operational and otherwise) of new observing systems? • To use observations on its own is not feasible. • Observational information must be assimilated by a model as information will have to be combined by other observations in time and space. • Information content carried by the model based on previous data is as large or larger than the actual observations on its own. • Observations must be controlled and filtered against an estimate, best provided by a dynamical projection of an ensemble of other data. Reanalysis and climate monitoring Lennart Bengtsson

  7. Re-analyses applications • Assessing the value of observing systems • Numerical weather prediction • Detection of climate change • Understanding the climate system Reanalysis and climate monitoring Lennart Bengtsson

  8. Re-analyses applications • Assessing the value of observing systems • Numerical weather prediction • Detection of climate change • Understanding the climate system Reanalysis and climate monitoring Lennart Bengtsson

  9. How the observations were used in the analysis (feedback) Input observations • Conventional • Surface • Upperair • Aircraft • Satellite products • Conventional feedback • Surface • Upperair • Aircraft • Satellite products NWP system Observations and observation equivalents from the model and analysis in database  Quality and departure information TOVS radiances TOVS feedback Bias modules SSMI feedback SSMI radiances AIRS radiances AIRS feedback O3 feedback O3 data (Input and feedback observations in BUFR code) Reanalysis and climate monitoring Lennart Bengtsson

  10. Erroneous CLIMAT data in CRUTEM2v, corrected in HadCRUT3 (Brohan et al., 2006) Inadequate SYNOP coverage in ERA-40 Comparison of reanalysis and land-station values Surface air temperature anomaly (oC) with respect to 1987-2001 Europe ERA-40 – CRUTEM2v Reanalysis and climate monitoring Lennart Bengtsson

  11. METEOSAT Reprocessed Winds Reanalysis and climate monitoring Lennart Bengtsson

  12. Re-analyses applications • Assessing the value of observing systems • Numerical weather prediction • Detection of climate change • Understanding the climate system Reanalysis and climate monitoring Lennart Bengtsson

  13. The principle of error reduction in data assimilation Reanalysis and climate monitoring Lennart Bengtsson

  14. Evolution of 1-Day Forecast Error, Lorenz Error Growth, and Forecast Skill for ECMWF Model(500 hPa NH Winter) 2007 8 1.2* 0.91 Reanalysis and climate monitoring Lennart Bengtsson

  15. Improvements in NWP from Miyakoda (1972) to 2002. Courtesy ECMWF How long to get to D+10 in winter? Reanalysis and climate monitoring Lennart Bengtsson

  16. The impact of observations on forecast skillExperiments with different observing systemsDJF 1990/91 using ERA40 observations • The control system (using all observations) • A terrestrial based system ( radio-sondes and aircraft obs.) • A satellite based system ( satellites and surface pressure) • A surface based system ( surface observations) Reanalysis and climate monitoring Lennart Bengtsson

  17. Global forecasts DJF 90/91 • 7- day forecasts, every 6hr. • Later ECMWF model T159/L60 • Extra-tropics 20-90N and 20-90S • 500 hPa Z, normalized SD for the period • Tropics 20N-20S • Wind vector field 850 and 250hPa Reanalysis and climate monitoring Lennart Bengtsson

  18. Observing systems and predictive skillNorthern Hemisphere extra-tropicsBengtsson and Hodges, 2004 Reanalysis and climate monitoring Lennart Bengtsson

  19. Observing systems and predictive skillSouthern Hemisphere extra-tropicsBengtsson and Hodges, 2004 Reanalysis and climate monitoring Lennart Bengtsson

  20. Observing systems and predictive skillTropics V 250 hPaBengtsson and Hodges, 2004 Reanalysis and climate monitoring Lennart Bengtsson

  21. Northern Hemisphere Ops 2003 Ops 1980 Ops 1980 Ops 1980 Ops 2001 Ops 2001 % ERA 2001 ERA 2001 Anomaly correlations of 500hPa height forecasts Northern Hemisphere % Reanalysis and climate monitoring Lennart Bengtsson

  22. Ops 2003 Ops 1980 Ops 2001 % ERA 2001 Anomaly correlations of 500hPa height forecasts Australia/New Zealand % Reanalysis and climate monitoring Lennart Bengtsson

  23. Re-analyses applications • Assessing the value of observing systems • Numerical weather prediction • Detection of climate change • Understanding the climate system Reanalysis and climate monitoring Lennart Bengtsson

  24. Linear trend in two-metre temperature (1979-2001) Mean over land: 0.32OC/decade Mean over land: 0.30OC/decade Based on ERA-40 reanalysis of SYNOP data (Simmons et al., 2004) Based on monthly CLIMAT station data (CRUTEM2v; Jones and Moberg, 2003) Reanalysis and climate monitoring Lennart Bengtsson

  25. Linear trend in two-metre temperature (1979-2001) 0.32OC/decade 0.27OC/decade Mean over land: 0.30OC/decade Based on ERA-40 reanalysis of SYNOP data, sub-sampled to match CRUTEM2V Based on monthly CLIMAT station data (CRUTEM2v; Jones and Moberg, 2003) Reanalysis and climate monitoring Lennart Bengtsson

  26. 500hPa temperature fits for two Antarctic stations Reanalysis and climate monitoring Lennart Bengtsson Radiosonde ERA-40

  27. CRUTEM2v (Jones and Moberg, 2003) ERA-40 Trend and variability in two-metre temperature Linear trend (1979-2001): CRUTEM2v 0.31OC/decade ERA-40 0.28OC/decade NCEP 0.19OC/decade Reanalysis and climate monitoring Lennart Bengtsson

  28. MSU-4 data analyzed by Mears et al. (2003) ERA-40 equivalent from Ben Santer Trend and variability in lower stratospheric temperature Linear trend: MSU-4 - 0.39OC/decade ERA-40 - 0.30OC/decade NCEP - 0.82OC/decade Reanalysis and climate monitoring Lennart Bengtsson

  29. Tropical water-vapour content Reanalysis and climate monitoring Lennart Bengtsson

  30. Re-analyses applications • Assessing the value of observing systems • Numerical weather prediction • Detection of climate change • Understanding the climate system Reanalysis and climate monitoring Lennart Bengtsson

  31. 1971 - 2000 90th percentile of significant wave height February m Global wave climatology atlas S. Caires, A. Sterl, G. Komen and V. Swail http://www.knmi.nl/onderzk/oceano/waves/era40/atlas.html Reanalysis and climate monitoring Lennart Bengtsson

  32. Hurricane Katrina August 2005ECMWF operational analyses, 850 hPa vorticity Reanalysis and climate monitoring Lennart Bengtsson

  33. Prediction of Atlantic hurricanes are influenced by ENSOResults from a general circulation model integrated over 30 years comparing active seasons from less active Temperature difference Measure of divergence ECHAM5/OM ERA-40 prediction verification Vertical wind shear Reanalysis and climate monitoring Lennart Bengtsson

  34. Challenges • Trends in the free atmosphere • The water cycle • Surface fluxes between the surface and the atmosphere • Extending the re-analyses back in time before upper air observations Reanalysis and climate monitoring Lennart Bengtsson

  35. ERA-40/ L60 ERA-Interim/ L91 81 km 65 km Reanalysis and climate monitoring Lennart Bengtsson

  36. ERA-Interim 1989  to continue as CDAS ERA-40 1957-2002 • Data-assimilation system T159L60  T255L91 New humidity analysis and improved model physics 3D-Var FGAT 12 hour 4D-Var • Satellite level-1c radiances Better RTTOV and improved use of radiances especially IR Assimilation of rain affected radiances from SSM/I Adaptive bias correction • Improved use of radiosondes Bias correction and homogenization based on ERA-40 • Correction of SHIP/ SYNOP surface pressure biases • Use of reprocessed Meteosat winds • New set of Altimeter wave height data 1991 Reanalysis and climate monitoring Lennart Bengtsson

  37. ERA-new ERA-40 Operations Much improved 500hPa height forecasts Anomaly correlation of 500hPa height, averaged for 12UTC forecasts from 1 January to 31 December 1989 Northern hemisphere Southern hemisphere Reanalysis and climate monitoring Lennart Bengtsson Day

  38. ERA-new ERA-40 Operations Much improved tropical 850hPa wind forecasts RMS error of vector wind, averaged for 12UTC forecasts from 1 January to 31 December 1989 vs analyses vs radiosondes Reanalysis and climate monitoring Lennart Bengtsson Day

  39. Global precipitation-evaporation 1989 (+12h forecast) ERA-Interim (test) = 0.01 ERA-40 = 0.23 ERA-40 23 year Climate = 0.32 Reanalysis and climate monitoring Lennart Bengtsson

  40. In summary • Reanalysis does have a role to play in the study of recent climate trends • It can help in the detection and correction of problems in the instrumental record • ERA-40 represents a clear step forward for the depiction of trends • Insights into deficiencies are provided by analysis and background fits to observations, analysis increments and comparisons with simulations and other reanalyses • There is considerable potential for improvement of reanalysis – more so than for improvement of the database of past observations? Reanalysis and climate monitoring Lennart Bengtsson

  41. Visions • Extending the re-analyses to incorporate the full 20th century. How feasible is this? • Extending re-analyses to the fully coupled climate system. • To incorporate bio-geochemical processes • Applying re-analyses ideas on other planetary atmospheres ( e.g Venus, Mars) Reanalysis and climate monitoring Lennart Bengtsson

  42. 500mb Height Analyses for 0Z 20 Dec 2001 Full NCEP Climate Data Assimilation System (CDAS) (120,000+ obs) Climatological Ensemble Filter (EnsClim) 1895 (308 surface pressure obs) RMS = 96 m CDAS-SFC obs only 1895 (308 surface pressure obs) RMS = 96 m Kalman / Ensemble Filter (EnsFilt) 1895 (308 surface pressure obs) RMS = 49 m 5500 m contour is thickened Reanalysis and climate monitoring Lennart Bengtsson

  43. Emission now 8PgC 2002-06 4.9 PgC annually ca.60% Reanalysis and climate monitoring Lennart Bengtsson

  44. ERA-70? ERA-Interim • Could start in 2010 depending on resources • ~ 1940  • Important components Recovery of observations Variational technique aimed for reanalysis Comprehensive adaptive bias handling Handling of model bias Improved SST & ICE dataset Reanalysis and climate monitoring Lennart Bengtsson

  45. Some comments to climate monitoring • Climate monitoring should be undertaken in an integrated mode applying the conceptual ideas from the re-analyses • Major efforts are needed to determine biases so overlapping of satellite sensors is needed as well as the use of complementary instruments ( e.g. GPS occultation versus temperature retrievals) • Operational time of particular instruments should ideally cover representative climate periods ( several decades) Reanalysis and climate monitoring Lennart Bengtsson

  46. END Any questions? Reanalysis and climate monitoring Lennart Bengtsson

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