Reanalysis-1 / Reanalysis-2

A global plot of Reanalysis-1 mean relative humidity for the month of January 1948. Notably arid regions of the globe are marked in deep shades of blue. This image was produced by downloading one file of Reanalysis-1 data through NOMADS and visualizing with the Grid Analysis and Display System (GrADS).

The National Centers for Environmental Prediction (NCEP) is involved with two global reanalysis projects in joint ventures with other organizations. The first is the NCEP/NCAR Reanalysis (Reanalysis-1), a global reanalysis of atmospheric data spanning 1948 to present. It was created in cooperation with the National Center for Atmospheric Research (NCAR). The second project is the NCEP/DOE Reanalysis (Reanalysis-2) project, a global reanalysis of atmospheric data spanning 1979 to present. It was created in cooperation with the Department of Energy (DOE). Gridded data from Reanalysis-2 are available through the NOAA National Operational Model Archive and Distribution System (NOMADS).

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A plot of Reanalysis-2 average monthly temperature for July 1979 by latitude and height (decreasing pressure surfaces). Temperatures are in degrees Kelvin (freezing is approximately 273K, or 0°C, or 32°F). Northern latitudes are to the right in this diagram. This image was produced by downloading Reanalysis-2 data through NOMADS then visualizing with NASA’s Panoply visualization tool.

Many data sources went into the generation of both reanalyses: surface observations, upper-air balloon observations, aircraft observations, and satellite observations. Both reanalyses are a global set of gridded weather data at a 2.5 degree by 2.5 degree horizontal resolution. The main difference between these two global reanalysis projects is the starting date of their period of records. The year 1979 was chosen as a beginning date with Reanalysis-2 as it coincides with the date of modern satellite weather ingest. Reanalysis-1 begins in the year 1948, and the data input pattern, better known as data assimilation, changes over the course of this reanalysis, making it an inconsistent (though still scientifically valid) reanalysis record due to there being no satellite ingest in the early part of the Reanalysis-1 dataset.

More information on Reanalysis-1 and Reanalysis-2 is available at the NCEP Reanalysis home pages.

Product Types

6-Hourly Reanalysis

Model	Grid/Scale	Period of Record	Model Cycle	Output Timestep	Data Access Links
6-Hourly Reanalysis-2	Global, 2.5deg by 2.5deg	01Jan1979 - 30Sep2005	Monthly	6-hourly, 00-18UTC	FTP HTTPS HAS

Monthly Means

Model	Grid/Scale	Period of Record	Model Cycle	Output Timestep	Data Access Links
Reanalysis-2 Monthly Means	Global, 2.5deg by 2.5deg	Jan1979 - Mar2006	Monthly	Monthly	FTP HTTPS HAS

Data Usage Notes

Ingest of Reanalysis-2 data at NCEI stopped with a complete, fixed period of record of 01Jan1979 through 30Sep2005. Additional Reanalysis-2 data may be obtained; please see the link to the Climate Prediction Center (CPC) Reanalysis-2 home page below.