The 20th Century Reanalysis Project

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The 20th Century Reanalysis Project

• Jeff Whitaker, Gil Compo, Nobuki Matsui and
  Prashant Sardesmukh
• NOAA/ESRL and Univ. of Colorado/CIRES

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The 20th Century Reanalysis

• What
• A 6-hourly reanalysis from 1892-present
  (1918-1949 done so far), using only surface
  pressure observations.
• Why
• No daily gridded tropospheric-wide circulation
  dataset before 1948 exists.
• Evaluate models, understand causes for 20th
  century climate variations (e.g. 30s U.S.
  drought, 20-40s polar warming).
• How
• 56 member Ensemble Kalman Filter, T26L28 CFS03
  model.
• Includes analysis error estimate.

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Feasibility OSE

• Subset of operational ps obs for DJF 2004/2005.
• EnKF with CFS at T62, 3DVar and 4DVar with ECMWF
  IFS at T159 (courtesy Jean-Noel Thepaut).
• OSE with 1998 GFS in Feb 2006 BAMS.

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EnKF Error34 m
NCEP Operational
EC 4DVar Error31 m
EC 3DVar Error104 m
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Mean and Spread Dec 1, 1918-1949
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1918-1948 24-h forecast skill
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1918-1948 24-h forecast skill
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1918-1948 24-h forecast skill
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Uncertainty estimate (blue actual O-F, red
expected O-F)
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T700 Verification - Independent Obs(courtesy S.
Bronniman and A. Grant, ETH)
MAE 1.58 K Expected Error 1.71 K
MAE 1.59 K Expected Error 1.73 K
Assumes observation error of 1.5 K
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Z500 Verification - Independent Ob(courtesy S.
Bronniman and A Grant, ETH)
MAE 25.8 m Expected Error 23.7 m
Assumes observation error of 20 m
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Sep 1938 New England Hurricane
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1930s U.S. Drought(Precip)
Analyzed Anomalies (1918-1948 base period) with
Z500 field
Observed Anomalies (1895-2000 base period)
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1930s U.S. Drought(Precip)
Analyzed Anomalies (1918-1948 base period) with
MSLP field
Observed Anomalies (1895-2000 base period)
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1930s U.S. Drought(Temperature)
Analyzed Anomalies (1918-1948 base period) with
Z500 field
Observed Anomalies (1895-2000 base period)
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Summary

• Accuracy Mid-tropospheric circulation fields
  about as accurate as a 3-day forecast today.
• Timeline 1918-1949 done, full 1892-present done
  by end of 2008.
• Data Access Will be freely available from NCAR,
  NOAA/ESRL and NOAA/NCDC. 1918-1949 in early
  2008, rest late 2008/early 2009.
• For status updates, email jeffrey.s.whitaker_at_noaa.
  gov or gilbert.p.compo_at_noaa.gov