Re-Analyses Data

The term "re-analysis" is derived from the numerical analysis that is used in weather forecasts. The re-analysis data are calculated with models (similar to the ones used for weather prediction), that assimilate quality-assured monitoring data. The data contain global fields in different height levels of various parameters and are calculated over a long time period using all the appropriate observations. The aim of the re-analysis is to get a homogeneous data set, with high temporal and spatial resolution, that is suitable for the calculation of climatologies, for example.

The most important re-analysis products are:

American reanalyses of National Center for Environmental Prediction (NCEP):

European re-analysis of  European Centre for Medium-Range Weather Forecast  (ECMWF):

  • ERA40
  • ERA Interim

Japanese re-analyses:

NASA Goddard Space Flight Center re-analysis:

A comprehensive collection of several reanalyses can be found on http://reanalyses.org/.

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In the context of weather forecasting, the data produced for 0 o'clock are typically referred to as analysis. They are quickly available, but the quality is not as well as for the re-analyses.

  • American predictions and analyses of GFS
  • European predictions and analyses of ECMWF

Comparison of Reanalyses

Name Organization Time period Resolution Data assi- milation method Comments
JRA-25 JMA/CRIEPI 1979 – present T106 L40, global 3D-Var Originally limited to 2004, then continued as JCDAS (real time operation)
ERA-15 ECMWF 1979 - 1993 T106 L31, global 3D-OI Successor of FGGE.
ERA-40 ECMWF 09/1957 - 08/2002 TL159 L60, global 3D-Var Successor of ERA-15
ERA Interim ECMWF 1979 - present T255 L60, global 12h 4D-Var Originally limited to 1989. Successor of ERA-40.
NCEP/NCAR Reanalysis R1 NCEP/NCAR 1948 - present T62 L28, global 3D-Var is operated as CDAS.
NCEP/DOE R2 (NCEP-DOE AMIP-II reanalysis) NCEP/DOE 1979-present T62 L28 3D-Var is operated as CDAS.
NCEP NARR - North American Regional Reanalysis NCEP 1979 - present 32km 29PL, North America
NCEP CFSR - Climate Forecast System Reanalysis NCEP 1979 - 2008 T382 L64
GEOS1 NASA/DAO 1980–1995 2° x 2.5° L20 3D-OI + IAU
NASA MERRA NASA 1979 - present 0.5°(lat) x 2/3° (lon) L72, global
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