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How extensive (long) should hindcasts be?

How extensive (long) should hindcasts be?. Huug van den Dool Climate Prediction Center, NCEP/NWS/NOAA Suranjana Saha Environmental Modeling Center, NCEP/NWS/NOAA. Explained Variance (%) Feb 1981-2001; lead 3 (Nov starts); monthly T2m (US, CD data).

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How extensive (long) should hindcasts be?

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  1. How extensive (long) should hindcasts be? Huug van den Dool Climate Prediction Center, NCEP/NWS/NOAA Suranjana Saha Environmental Modeling Center, NCEP/NWS/NOAA

  2. Explained Variance (%) Feb 1981-2001; lead 3 (Nov starts); monthly T2m (US, CD data) Explained Variance=Square of Anom Correlation SEC : Systematic Error Correction; EW: Equal Weights CFS=CFS, USA; EC=ECMWF; PLA=Max Planck Inst, Germany; METF=MeteoFrance, France; UKM=UKMetOffice; INGV=INGV, Italy, LOD=LODYC, France; CERF=CERFACS, France

  3. Anomaly Correlation (%) Feb 1981-2001; lead 3 (Nov starts); monthly T2m (US, CD data) WITH SEC21 WITH SEC8 SEC8-SEC21 Need more years to determine the SEC where/when the inter annual standard deviation is large SEC : Systematic Error Correction

  4. CONCLUSIONS • Without SEC (systematic error correction) there is no skill by any method (for presumably the best month: Feb) • With SEC (1st moment only), there is skill by only a few models (5 out of 8 are still useless) • MME not good when quality of models varies too much • MME3 works well, when using just three good models

  5. CONCLUSIONS (contd) • CFS improves the most from extensive hindcasts (21 years noticeably better than 8) and has the most skill. Other models have far less skill with all years included. • Cross validation (CV) is problematic (leave 3 years out when doing 8 year based SEC?) • Need more years to determine the SEC where/when the inter annual standard deviation is large

  6. 15-member CFS reforecasts 15-member CFS reforecasts

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