Climate Models and Reanalysis Data

Intro to Reanalysis Data

Reanalysis Data - Wind SpeedReanalysis is a scientific method for developing a comprehensive and consistent record of how the weather and climate are changing over time.  Reanalysis data relies on the assimalation of sensor data from multiple sources and numerical weather prediction models to produce a continually updated, gridded data set that describes the state of the Earth’s atmosphere at difference points in time and space.  Gridded reanalysis data is available from different sources.  The different data sources vary with respect to

  • spatial resolution,
  • time resolution,
  • the number of variables modeled,
  • the relative degree to which different sensor networks are used to produce the reanalysis data, and
  • the length of the historic data record.

Reanalysis data typically extends over several decades or longer, and covers the entire globe from the Earth’s surface to well above the stratosphere.  In practice, reanalysis data is frequently used as “observations” or the “true state” of the atmosphere when studying short-term variability and long-term changes. However, its is important to stress that reanalysis data may suffer from inconsistencies in the data collection system and biases in the assimilation or numerical models.  As a result, in certain locations, such as complex mountains, reanalysis data may have spurious trends. These issues can be addressed to some extent by comparing the output from different reanalyses, and comparing reanalysis output to independent sensor data.

Reanalysis Data Comparison Table

The following table compares the different reanalysis data sets available.  Click to enlarge.



ECMWF ERA Interim Reanalysis (1979-Present)

ecmwf_logoERA-Interim is supplied by the European Centre for Medium Range Forecasts (ECMWF) and was originally planned as an ‘interim’ reanalysis in preparation for the next-generation extended reanalysis data to replace ERA-40. It uses a December 2006 version of the ECMWF Integrated Forecast Model (IFS Cy31r2). It originally covered dates from 1 Jan 1989 but an additional decade, from 1 January 1979, was added later. ERA-Interim is being continued in real time. The spectral resolution is T255 (about 80 km) and there are 60 vertical levels, with the model top at 0.1 hPa (about 64 km).
1. Home Page
2. Data Downloads

NCEP/NCAR Reanalysis 1  (1948-Present)

NCARlogo1NOAA’s first generation reanalysis data was the first of it’s kind. The NCEP/NCAR reanalysis model is initialized with a wide variety of weather observations: ships, planes, RAOBS, station data, satellite observations and many more. By using the same model, scientists benefit from a consistent use of data and scientific results without the complication that model changes can cause. The dataset is kept current using near real-time observations.
1. Main Page
2. Pressure Level
3. Surface
4. Surface Fluxes
5. Other Fluxes
6. Tropopause
7. Derived Data
8. Spectral Coefficients
9. Direct FTP

NCEP-DOE Reanalysis 2 (1979-Near Present)

PrintNCEP, in conjunction with the US Department of Energy, produced a second version of their reanalysis data set starting from the beginning of the major satellite era. More observations were added, assimilation and resolution errors were corrected, and a better version of the reanalysis model is used.
1. Main Page
2. Pressure
3. Gaussian Grid
4. Spectral Coefficient Data
5. Surface Data
6. Search for Gridded Data
7. Direct FTP : Pressure (4x daily)
8. Direct FTP: Gaussian Grid (4x daily)
9. Direct FTP: Spectral Coefficients (4x daily)
10. Direct: FTP: Surface Data (4x daily)

NCEP CFSRR (1979-Present)

CFSRRlogoThe Climate Forecast System Reanalysis and Reforecast project is a third generation reanalysis product from NCEP. It is a global, high resolution, coupled atmosphere-ocean-land surface-sea ice system designed to provide the best estimate of the state of these coupled domains.  CFS uses the latest scientific approaches for assimilating observations from many data sources, including satellite data for solar radiances, CO2, trace gases and aerosols.  CFS also offers finer data resolutions.  CRS is disadvantaged when compared to other realanysis data sets since relatively few evaluations have been conducted so the performance is not as well-known.
1. NOAA Intro Page
2. CFS Homepage
3. CFS Documentation
4. CFS Data Access
5. Direct FTP
6. Direct HTPP

NASA/GEOS MERRA Reanalysis (1979-Present)

merraflood93MERRA is a NASA reanalysis for the satellite era using a major new version of the Goddard Earth Observing System Data Assimilation System Version 5 (GEOS-5). The Project focuses on historical analyses of the hydrological cycle on a broad range of weather and climate time scales.  MERRA data places the NASA EOS suite of observations in a climate context.  The model benefits from NASA’s improved land surface data and significantly expands the number of vertical data levels describing Earth’s atmosphere.
1. MERRA Products
2. Data Subsetitng Tool: Daily Product
3. Data Subsetting Tool: Monthly Product
4. Direct FTP : Daily Product
5. Direct FTP: Monthly Product
6. Direct FTP: Diurnal Product

NASA/GOES MERRA2 (1980-Present)

NASA_Goddard_footerMERRA2 is a NASA reanalysis for the satellite era using a major new version of the GEOS-5 produced by the NASA Global Modeling and Assimilation Office (GMAO). MERRA2 will assimilate observations not available to MERRA, and therefore, will provide the extension of MERRA into the future. Since there are numerous improvemnts and updates to the data assimilaiton, model and observing system, it will be redone from the begining of wide satellite data availability and continue beyond MERRA’s terminus. Production is anticipated to begin in Nov 2013 and continue for one year.
1. MERRA Blog
2. Data Access: TBD

NOAA-CIRES 20th Century Reanalysis V2 (1871-2011)

CIRESlogoThe 20th Century Reanalysis version 2 dataset contains global weather conditions and their uncertainty in six hour intervals from the year 1871 to 2010.  Additional observations and a newer version of the NCEP model that includes time-varying CO2 concentrations, solar variability, and volcanic aerosols are used in version 2. The long time range of this dataset raises fundamental questions about data quality and the true behavior of climate processes such as the Pacific Decadal Oscillation and the Atlantic Multidecadal Oscillation.  Notwithstanding, the NCEP data is widely referenced by climate scientists.
1. Home Page
2. Documentation
3. Additional Dataset details
4. 4x Daily Product: Pressure
5. 4x Daily Product: Single Level

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