1. The 20th Century Reanalysis Project Jeff Whitaker, Gil Compo, Nobuki Matsui and Prashant Sardesmukh NOAA/ESRL and Univ. of Colorado/CIRES

2. 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. 30’s U.S. drought, 20-40’s polar warming). How: –56 member Ensemble Kalman Filter, T26L28 CFS03 model. – Includes analysis error estimate.

3. Feasibility OSE Subset of operational p s 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.

4. EnKF Error=34 m EC 4DVar Error=31 m EC 3DVar Error=104 m NCEP Operational

5. Mean and Spread Dec 1, 1918-1949

6. 1918-1948: 24-h forecast skill

9. Uncertainty estimate (blue actual O-F, red expected O-F)

10. T700 Verification - Independent Obs (courtesy S. Bronniman and A. Grant, ETH) MAE = 1.59 K Expected Error = 1.73 K* MAE = 1.58 K Expected Error = 1.71 K* * Assumes observation error of 1.5 K Anom Corr = 0.87Anom Corr = 0.90

11. Z500 Verification - Independent Ob (courtesy S. Bronniman and A Grant, ETH) * Assumes observation error of 20 m Anom Corr = 0.96 MAE = 25.8 m Expected Error = 23.7 m*

12. Sep 1938 New England Hurricane

13. 1930’s U.S. Drought (Precip) Observed Anomalies (1895-2000 base period) Analyzed Anomalies (1918-1948 base period) with Z500 field

14. 1930’s U.S. Drought (Precip) Observed Anomalies (1895-2000 base period) Analyzed Anomalies (1918-1948 base period) with MSLP field

15. 1930’s U.S. Drought (Temperature) Observed Anomalies (1895-2000 base period) Analyzed Anomalies (1918-1948 base period) with Z500 field

16. 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@noaa.gov or gilbert.p.compo@noaa.gov jeffrey.s.whitaker@noaa.gov gilbert.p.compo@noaa.gov