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New dataset of highly resolved atmospheric forcing fields for 1850-2009

New dataset of highly resolved atmospheric forcing fields for 1850-2009 Frederik Schenk & Eduardo Zorita. Working Packages. ANALOG RECONSTRUCTION. 1957 - 2007. 1850 - 2009. Motivation. I. Climatic aspects extention back to 1850: „Rebound from Little Ice Age“

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New dataset of highly resolved atmospheric forcing fields for 1850-2009

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  1. New dataset of highly resolved atmospheric forcing fields for 1850-2009 Frederik Schenk & Eduardo Zorita

  2. Working Packages ANALOG RECONSTRUCTION 1957 - 2007 1850 - 2009

  3. Motivation • I. Climatic aspects • extention back to 1850: „Rebound from Little Ice Age“ • e.g. changes of ocean climate 1850 – 1900? • long period prior to large human impact (i.e. nutrient loads) • II. Methodical aspects • avoid spatiotemporal interpolation • daily resolution using long historical station data since 1850 • high spatial resolution of 0.25° x 0.25° for N-Europe • reconstruct „full“ variability + extremes • linear regression yields variability << 50% (von Storch et al. 2004) • non-linear approach  Analog-Method von Storch et al. (2004): Reconstructing Past Climate from Noisy Data. Science, Vol. 306, No. 5696, pp. 679-682.

  4. Outline • - Short introduction of the Analog-Method • - Used data for the reconstruction • - Results & reconstruction skills • - Recommendations & limitations

  5. The Analog-Method 1) Generate consistent Analog fields = numerical downscaling 2) Find Analog fields for station data = statistical upscaling Zorita & von Storch (1999): The Analog Method as a simple statistical Downscaling Technique: Comparison with more complicated Methods. Journal of Climate, Vol. 12.

  6. ANALOGS … 1957-01-01 2007-11-30 Analog-Method: find for : 1850 2009 Reconstruction PREDICTOR (station data) …

  7. Settings • Test: Cross-wise cal/val for 25 years • Predictand = daily analogs from RCAO model • Predictor = SLP (N=23 stations, daily resolution) • Predictor = T2m (N=22 stations, only monthly) • Increase sample size for analogs (~4500/mon): • days of month m analogs in M {m-1, m, m+1} • allows seasonal shifts if forced by predictor • BUT: doesn‘t work for daily temperature... 

  8. Used Data Timeseries: Measurements Analog-Fields: Regional Model Output

  9. Analogs of Atmospheric Fields • Atmospheric Fields for: • Sea-Level-Pressure [Pa] • U- and V-Winds [m/s] • Relativ Humidity [%] • Total Cloud Cover [%] • Precipitation [mm] • Temperature [K] Source RCAO Swedish Regional Climate Model with Coupled Ocean-Model for Baltic Sea

  10. Daily SLP Station Data • EMULATE Mean Sea Level Pressure data set (EMSLP) •  provides 86 stations (~ 20 for RCAO-domain) •  partly covers 1850 - 2002, updates from WMO etc. Ansell, T. J. et al. (2006) Daily mean sea level pressure reconstructions for the European - North Atlantic region for the period 1850-2003', Journal of Climate, vol 19, No. 12, pp 2717-2742.

  11. Missing Data Total N = 23 stations

  12. Results & Reconstruction Skills Calibration-Validation for 1958-1983 vs. 1984-2007 Calibration for final Reconstruction 1958-2007 Reconstruction for 1850-2009

  13. SLP  SLP-fields Fieldcor for JUN 1958-1983 Fieldcor for JAN 1958-1983 Calibration: 1984-2007

  14. SLP  U-Wind-fields Fieldcor for JUN 1958-1983 Fieldcor for JAN 1958-1983 Calibration: 1984-2007

  15. SLP  Precipitation Fieldcor for JUN 1958-1983 Fieldcor for JAN 1958-1983 Calibration: 1984-2007

  16. SLP  Rel. Humidity Fieldcor for JUN 1958-1983 Fieldcor for JAN 1958-1983 Calibration: 1984-2007

  17. SLP  Tot. Cloud-Cover Fieldcor for JUN 1958-1983 Fieldcor for JAN 1958-1983 Calibration: 1984-2007

  18. Analysis of Daily Wind Speed Wind speed distribution 99% treshhold values

  19. Histcount for wind speed January (N = 1550) number of events T-Test and F-Test for 0.01: no significant difference

  20. Histcount for wind speed July (N = 1550) number of events T-Test and F-Test for 0.01: no significant difference

  21. 99 Percentiles of Wind Speed 99% treshold values for daily wind speed for JANUARY (1958-2007) RCAO RECONSTRUCTION

  22. 99 Percentiles of Wind Speed Deviation of 99% treshold values for daily wind speed (REC – RCAO)

  23. 99 Percentile of wind speed 99% treshold for wind speed [m/s] Deviation of 99% treshold [m/s] T-Test and F-Test for 0.01: no significant difference

  24. Temperature Reconstruction weak physical link to SLP  alternative reconstruction

  25. Temperature – Struggle within • SLP is weak physical predictor for daily T2m • e.g. climate change = ΔT2m but ≠ ΔSLP • no daily T2m data available prior to 1900 • BUT monthly T2m is available from 1850 • Idea: T2m predictor  monthly T2m-field-reconstr. • Add daily T2m-anomalies reconstructed by SLP • Result: 100% daily variance, good monthly CC • BUT low daily correlation, low auto correlation

  26. SLP+T2m  Temperature With use of monthly T2m predictor Reconstruction by SLP only

  27. Recommendations & Limitations Who should use the data?

  28. Daily vs. Monthly Scale • Monthly scale: • - all variables are showing promising skills • Daily scale: • - SLP, WIND, CLOUDS show very good skills • - PREC, HUMIDITY good in DJFM, satisfying JJA • - T2m problematic

  29. Reconstruction Skills

  30. Thank you!„No data = no problems“ time is over ;-)

  31. Special Thanks to • Lars Bärring (SMHI) • Tuija Ruoho-Airola (FMI Helsinki) • Ari Venäläinen (FMI Helsinki) • Christine Luge (University of Jena) • Gerard van der Schrier (ECA&D)

  32. Analog-Method Stat. Downscaling Stat. Upscaling Sample of Analogs PREDICTOR PREDICTAND PREDICTAND PREDICTOR Zorita & von Storch (1999): The Analog Method as a simple statistical Downscaling Technique: Comparison with more complicated Methods. Journal of Climate, Vol. 12.

  33. T2M monthly means SLP daily anomalies

  34. SLP  T2m ?

  35. Best-Of „Missmatches“

  36. Best-Of „Missmatches“

  37. 15th of April 2007 Atmospheric Blocking: Similar SLP-pattern can cause warm and cold T2m effects, i.e. in spring

  38. Short Wave radiation in ECHO-G

  39. Short Wave radiation in ECHO-G

  40. 99% Treshhold for daily Rain 99% treshold values for daily precipitation for JANUARY (1958-2007) RCAO RECONSTRUCTION

  41. 99% REC - RCAO Deviation of 99% treshold values for daily precipitation (REC – RCAO)

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