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RE-ANALYSIS at ECMWF:

RE-ANALYSIS at ECMWF:. Status of ERA-40 Conclusions to date from ERA-40 Plans Adrian Simmons, Sakari Uppala and the ERA-40 team. ERA-40 (www.ecmwf.int/research/era). A re-analysis from September 1957 to August 2002

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RE-ANALYSIS at ECMWF:

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  1. RE-ANALYSIS at ECMWF: Status of ERA-40 Conclusions to date from ERA-40 PlansAdrian Simmons, Sakari Uppala and the ERA-40 team

  2. ERA-40 (www.ecmwf.int/research/era) • A re-analysis from September 1957 to August 2002 • Based on cycle 23r4 of ECMWF forecasting system - operational from June 2001 to January 2002 • Six-hourly 3D-Var analysis - operations uses 12-hourly 4D-Var • T159 horizontal resolution (~125km grid) - operations uses T511 (~39km grid)

  3. ERA-40 – External collaboration • Most of the older observations were supplied by NCAR via NCEP • EUMETSAT supplied reprocessed satellite winds (NESDIS did not) • Sea-surface temperature and sea-ice analyses were produced by the Met Office and NCEP • Validation partners (formal and informal) provided valuable feedback on plans and performance • External support came from EU, Fujitsu, IAP, JMA, PCMDI, WCRP, GCOS, …

  4. ERA-40 – Status • Production was completed in April 2003 • Much use made of data already in Europe via direct access to ECMWF archives and national data centres • 2.5o data are available on a public data server (www.data.ecmwf.int/data) • Data will be supplied to NCAR for UCAR use and general use in USA for research and education • Observations have been supplied to Japanese Meteorological Agency for use in JRA-25

  5. ERA-40 – ongoing activities • Documentation • Observation-related studies and reprocessing • Diagnosis of analyses • Production of atlas with Met. Dept., Reading University • Completion of twice-daily 10-day forecasts • “AMIP-style” run using ERA-40 model, boundary fields and forcings • Development of an updated reanalysis system

  6. Conclusions from ERA-40 – In-situ observations • Obvious deficiencies in collection of SYNOPS for early years • Encoding errors have been a source of delay and deficiency • Some observation types mis-assigned • Elimination of duplicates needs refinement • More work needed on bias correction (applied only to radiosonde temperatures from 1979 onwards)

  7. Conclusions from ERA-40 – General synoptic quality of analyses • Best for most recent years • Quite good throughout the period for the northern hemisphere troposphere and lower to middle stratosphere • Poor in southern hemisphere in early years • Some improvement in early 1970s • Big improvement in 1979

  8. Ops 2002/3 Ops 1980 Ops 1980 Ops 1980 Ops 2001 Ops 2001 ERA 2001 Anomaly correlations of 500hPa height forecasts Northern Hemisphere %

  9. Ops 2002/3 Ops 2001 Ops 1980 Anomaly correlations of 500hPa height forecasts Australia/New Zealand %

  10. Trends and interannual variability • Clear improvement on ERA-15 • Global temperature trends reasonably well captured from surface to lower stratosphere • Caution needed when looking at regional trends • Interpretation needs knowledge of • model biases • observation biases • observation coverage • analysis system

  11. CRU/Hadley Centre http:///www.cru.uea.ac.uk/cru/info/warming Trends and interannual variability ERA-40

  12. 1958-1968 1969-1979 1980-1990 1991-2001 Trends and interannual variability Anomaly in 2m temperature oC

  13. 1958-1968 1969-1979 1980-1990 1991-2001 Trends and interannual variability Anomalies in 2m temperature and 500hPa height oC

  14. 1958-1968 1969-1979 1980-1990 1991-2001 Missing SYNOPs Trends and interannual variability Anomaly in 2m temperature oC

  15. Trends and interannual variability Global-mean ERA-40 500hPa temperature Time series of MSU-2 brightness-temperature anomaly (K), from Wentz and colleagues Image produced by Remote Sensing Systems and sponsored by NOAA Climate and Global Change Program

  16. No sonde bias correction before 1979 VTPR bias correction problem Cold bias around southern winter pole in early years Parker & Alexander (2002) Trends and interannual variability Global-mean ERA-40 70hPa temperature

  17. Hydrological cycle • Relatively low biases and good interannual variability in extratropical precipitation from short-range forecasts • Excessive rainfall over tropical oceans in satellite era: • increases as more data are assimilated • compounded by misinterpretation of Pinatubo aerosols • Water vapour over tropical oceans: • model biased dry compared with IR and MW data • analyses biased moist compared with SSM/I retrievals • Problems are: • model biases • observation biases and inhomogeneity of coverage • how to distribute analysis increments in horizontal and vertical

  18. OBS ERA-40 Precipitation over the Baltic catchment area (1981-2001)

  19. South-east Asia Tropical Africa Tropical America Equatorial Pacific Comparison with monthly-mean GPCP precipitation rates (1979-2001) Europe North America North Atlantic Arctic

  20. Aspects of tropical humidity analysis 0-6h forecasts Year

  21. ERA-40 SSM/I retrievals from Remote Sensing Systems Analysis Pinatubo Tighter QC of HIRS 0 - 6h forecast Aspects of tropical humidity analysis Year

  22. ERA-40 SSM/I retrievals from Remote Sensing Systems 24h forecast 24 - 36h forecast Aspects of tropical humidity analysis Year

  23. Stratosphere • QBO handled well • Several problems with temperature biases • due both to model biases and difficulties in radiance assimilation • worse in ERA-40 3D-Var than in operational 4D-Var • Too-strong Brewer-Dobson circulation • seen in humidity, and ozone when TOMS/SBUV data not assimilated • worse when model temperature biases are corrected by radiance assimilation

  24. Gan (1S, 73E) Representation of the QBO Canton Island (3S, 171W) 30hPa

  25. Severe SSU difficulties Warm model bias Bad VTPR bias-correction Cold analysis bias Global-mean temperature at 1hPa and 3hPa NOAA-3 1hPa Pre-satellite VTPR SSU AMSU 3hPa

  26. SSU-3 2hPa 5hPa SSU-2 SSU-1 100hPa MSU-4 North Pole Latitude South Pole Zonal-mean temperature difference January 1989 – January 1981 1hPa 10hPa 100hPa Model level Polar Polar problem marked from autumn 1998 onwards (with AMSU-A added) in ERA-40 but not operations

  27. 1 Model simulation 10 Breaks in production hPa 100 One year Equatorial specific humidity

  28. Blue: ERA-40 (TOMS and SBUV data assimilated 1979-1988 and 1991-2002) Red: Ground-based measurements (NOAA/CMDL) Total Ozone (Monthly means from1957 to 2002) (following Pascal Simon, Météo-France)

  29. Plans beyond ERA-40 • An interim reanalysis • Start next year, T159L60, latest version of forecasting system • Run from 1991 (tbd) onwards, continued in close to real time • Baseline for ongoing developments (e.g. constituent analysis) • Experimentation • observing system experiments • high-resolution 4D-Var analyses for specific cases • to validate new versions of forecasting system • Development of observational data base and processing software • An extensive new reanalysis in 2008 or beyond

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