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HOME > Monitoring and Data > Oceanic & Atmospheric Data > Reanalysis Project
NCEP/NCAR Reanalysis Project (CDAS)
Sea-Ice Rerun
TOVS-Land Rerun
Regional Reanalysis
Plots and Data
CDAS On-Line Data
What is It All About?
Things are Not Perfect ... Problem Report
How to Get the Data
12/22/2011: Bad snow analyses for 12/18/2011 and 12/19/2011. In process of rerunning.
4/01/2005: Reran CDAS from 2004080100 to 2004032212 because of a problem with the use of the sea-ice analyses. Please replace all v1.0 CDAS data with the new version. More details are available.
7-7-2003: Reran CDAS From 2003050900 to 2003062618 because much of the satellite data was missing for two days. Please replace all v1.0 CDAS with the new version. The lack of ATOVS data produced a cooling in the 200-50 mb level in the tropics as well as minor warming in the mid-troposphere and cooling in at the 850 mb level as shown here.
5-12-2003: Minor port, moved CDAS to new IBM computer (frost/snow) starting with the 2003050818 analyses. This is the fifth change in computers.

SEA-ICE Problem: Rerun from 8/2004 to 3/2005

The Sea-ice problem has been fixed. The datasets need to be updated to the revised analyses (Aug 1, 2004-March 22, 2005). This same problem affected the NCEP/DOE Reanalysis and the operational spectral model

TOVS Problem: Rerun from 3/97 to 9/2001

The TOVS-land problem has be rerun. The data sets have been updated to the revised analyses (March 1, 1997-Sept 18, 2001).
detailed summary of observational data used by Reanalysis.
background error used by the assimilation system (SSI).
1/3/2000: Y2K problem: some observational data were being incorrectly rejected. This problem only affected the 12/31/1999 analyses were fixed 1/3/2000 (6pm).
News: Found a "truncation" error with the snow analyses. Fixed Dec 1. More details to follow.
Rotating Archives
CDAS is now updated daily and the daily updates are being stored in the "CDAS rotating archives." These archives include more data than in our on-line historical archives such as four times daily analyses and more daily-averaged fields. The historical archives will continue to be updated once a month.
Annual Reanalysis CD-ROMs
1950-2003 Reanalysis CD-ROMs are now available. Contact NCAR for more information.
The Reanalysis Synoptic CD-ROM with global 00Z analyses from 1979-1996 is available. Fields on this CD-ROM include HGT (1000 mb, 500 mb), WINDS (850 mb, 200mb) and OMEGA (500 mb). This CD-ROM, like the annuals, is GrADS compatible and includes an MS-DOS menu system and is available from NCAR.
  What is it all about ?
The NCEP/NCAR Reanalysis Project is a joint project between the National Centers for Environmental Prediction (NCEP, formerly "NMC") and the National Center for Atmospheric Research (NCAR). The goal of this joint effort is to produce new atmospheric analyses using historical data (1948 onwards) and as well to produce analyses of the current atmospheric state (Climate Data Assimilation System, CDAS).
Until recently, the meteorological community has had to use analyses that supported the real-time weather forecasting. These analyses are very inhomogeneous in time as there have been big improvements in the data assimilation systems. This played havoc with climate monitoring as these improvements were often produced changes in the apparent "climate". Even fundamental quantities such as the strength of the Hadley cell has changed over the years as a result of the changes in the data assimilation systems.
The quality and utility of the re-analyses should be superior to NCEP's original analyses because
a state-of-the-art data assimilation is used
more observations are used
quality control has been improved
the model/data assimilation procedure will remain essentially unchanged during the project
many more fields are being saved (ex. potential vorticity on isentropic surfaces, diabatic heating)
global (some older analyses were hemispheric)
better vertical resolution (stratosphere)
For more information ...
Blue Triangle 1996 BAMS Paper (Bulletin of the American Meteorological Society)
Blue Triangle 2001 BAMS Paper (Bulletin of the American Meteorological Society) (https)
Blue Triangle Misc. abstracts
Blue Triangle Types of Reanalysis Data
Blue Triangle Proc. of the First WCRP Intl. Conf. on Reanalysis (Silver Spring MD, 27-31 Oct 1997) WCRP-104, WMO/TD-No. 876
Blue Triangle Reanalysis prior to 1958
Blue Triangle The effect of satellite and aircraft data on Reanalysis (pdf)
Blue Triangle Detailed summary of observational data used by Reanalysis.
Blue Triangle Background error used by the assimilation system (SSI).
Feb 5 1999: Jan. 1999 CDAS is being rerun. A change in buffer table caused the GOES not to be used.
Problems with March 1997-December 1997 reanalyses were found which will require a rerun of the affected months. The problem is with the inclusion of too much Indian station data. More details are available.
Problems with aircraft winds used for 1976-1978 were discovered and the rerun was completed Jan 8, 1997. The aircraft data were transposed E-W which reduced the anomaly correlation by 5 points in a 5 day forecast. The effect of this bad jet-level data should be less severe in the lower troposphere. This web site will have the updated data after an examination and the Phoenix AMS meeting.
The "final" TOGA-COARE (Nov92-Feb93) analysis still needs to be rerun. The data on this web server is an interim analysis which doesn't use the TOGA-COARE data. Tapes from NCAR and CDC was well as the annual CD-ROMs contain the first version which is cold over the TOGA-COARE region.
Pre-QC observations counts are now available.
IBM/SP CDAS: Starting with May 1, 2000 Analyses Causes Changes.
Things are Not Perfect . . . Problem Report:
  • The Annual CD-ROM Demo Program Put the Wrong Date on Sample Plot 4 (Daily OLR).
  • 1976-1978 Rerun was Completed Jan. 9, 1998. This rerun corrects an error in positioning of some aircraft data (E/W transposed) New!
  • Poorly Encoded Surface/Mean-Sea-Level Pressure Observations were Rejected (1948-1967).
  • GRBSANL Grid was Misidentified.
Show Me the Data
Data Sources
Reading the Data
Other Related Sites:
arrow NCEP/AMIP-II DOE Reanalysis (Reanalysis-2)
arrow North American Regional Reanalysis (NARR)
arrow NCAR's page on NCEP/NCAR Reanalysis (Data, Documentation)
arrow CDC's Page on NCEP/NCAR Reanalysis (Plots, Data, Documentation)
arrow ECMWF Reanalysis Project (ERA-40) New!
arrow NCDC Cards Project
arrow Japanese 25-Year Reanalysis Project (JRA-25) New!
arrow Precipitation Intercomparison Project-3 Includes Reanalysis
arrow Climate Prediction Center Data Page (NCEP) (Plots, Data)
arrow IRI: CDAS/Reanalysis (Plots, Data)
arrow IRI: Climate Data Library
arrow GrADS
arrow Bob Kistler's Web Page (Includes Interesting Studies on Reanalysis)
arrow Land Mask, Elevation
arrow Random Notes on Reanalysis
arrow Portable Versions of Reanalysis Software
arrow Site Index (wgrib, grib2ctl, Reanalysis Random Notes)
Chain of Command:
arrow Department of Commerce
arrow National Oceanic and Atmospheric Administration 
arrow National Centers for Environmental Prediction
arrow Climate Prediction Center arrow Environmental Modeling Center
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Page last modified: November 5, 2002
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