The 20th Century

Reanalysis Project

Jeff Whitaker, Gil Compo, Nobuki Matsui and Prashant

Sardesmukh

NOAA/ESRL and Univ. of Colorado/CIRES

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.

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.

EnKFError=34 m

EC 4DVarError=31 m

EC 3DVarError=104 m

NCEPOperational

Mean and Spread Dec 1, 1918-1949

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1918-1948: 24-h forecast skill

1918-1948: 24-h forecast skill

1918-1948: 24-h forecast skill

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

T700 Verification - Independent Obs(courtesy S. Bronniman and A. Grant, ETH)

MAE = 1.59 KExpected Error = 1.73 K*

MAE = 1.58 KExpected Error = 1.71 K*

* Assumes observation error of 1.5 K

Anom Corr = 0.87 Anom Corr = 0.90

Z500 Verification - Independent Ob(courtesy S. Bronniman and A Grant, ETH)

* Assumes observation error of 20 m

Anom Corr = 0.96

MAE = 25.8 mExpected Error = 23.7 m*

Sep 1938 New England Hurricane

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1930’s U.S. Drought(Precip)

Observed Anomalies(1895-2000 base period)

Analyzed Anomalies(1918-1948 base period)with Z500 field

1930’s U.S. Drought(Precip)

Observed Anomalies(1895-2000 base period)

Analyzed Anomalies(1918-1948 base period)with MSLP field

1930’s U.S. Drought

(Temperature)

Observed Anomalies(1895-2000 base period)

Analyzed Anomalies(1918-1948 base period)with Z500 field

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