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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). Many data sources went into the generation of both reanalyses:  surface observations, upper-air balloon observations, aircraft observations, and satellite observations. Data from both reanalyses are available as 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. Gridded data from both Reanalysis-1 and Reanalysis-2 are available through NOMADS. More information on Reanalysis-1 and Reanalysis-2 is available at the NCEP Reanalysis homepages.

A scatter plot of Reanalysis-1 global 1000hPa (near-surface) temperatures versus global 850hPa (about 5000 feet) temperatures for June 1, 1952. Temperatures are in degrees Kelvin. This plot shows the general tendency of temperatures at 5000 feet to follow the trend of air temperatures close to the surface. Generally, the temperatures at the two levels are said to be well correlated. Correlation does not imply causality. This plot was generated by downloading a Reanalysis-1 file through NOMADS and visualizing the data with GNU Octave, an open-source software set similar to Matlab.

A plot of average monthly temperature by latitude and height (decreasing pressure surfaces). Temperatures are in degrees Kelvin (freezing is approximately 273 degrees Kelvin, or 0 degrees Celsius, or 32 degrees Fahrenheit). 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.