Climate Data

NCEP-NCAR (R1): An Overview

NCEP-NCAR (R1) is the original reanalysis effort. It uses a frozen global state-of-the-art global data assimilation system (as of 11 January 1995). The original database was enhanced (additional, quality checked datasets) by NCAR's Data Support Section. Originally planned to span 1957-96 ("40-Year Reanalysis Project"), it was extended back to 1948 and continues to this day.

Key Strengths:

  • Global Data Set
  • Longest running reanalysis that uses rawindsonde data
  • Used in many publications so it can be used as a baseline reference for many computations

Key Limitations:

  • Antiquated (1994) data assimilation/model
  • Low spatial and temporal moisture variability over oceans (mainly model 'first guess' fields)
  • relatively poor Southern Hemisphere

Technical Notes

Kalnay et al (1996) provide a four class partitioning of the R1 output analyzed variables. Specifically:

  • Class A: Variables that are "strongly influenced" by observations. 
  • Class B: Variables where both observations and the model influence the output (e.g., humidity and surface temperature).
  • Class C: Variables created by the model and data assimilation schemes (e.g., clouds and precipitation).
  • Class D: Fixed climatological values.

Years of Record

1948/01 to 2022/06
temporal metadataID:



Sub-daily | Daily | Monthly

Data Time Period Extended?

yes, data set is extended


Spatial Resolution

2.5°x2.5°; 3 hPA top

Ocean or Land


Missing Data Flag

spatially complete

Data Assimilation Method

Model Resolution used to create reanlaysis

T62 - 28 levels

Model Vintage (reanalysis)


Input Data

Rawindsondes; ICOADS, station data, aircraft, satellite retrievals

Earth system components and main variables

Data Access: Please Cite data sources, following the data providers' instructions.

Usage Restrictions

varies by download site
  1. Kalnay et al.,1996: The NCEP/NCAR 40-Year Reanalysis Project. Bull. Amer. Meteor. Soc., 77, 437–471.
  2. Kistler, R., et al, 2001: The NCEP-NCAR 50-Year Reanalysis: Monthly Means CD-ROM and Documentation. Bull. Amer. Meteor. Soc., 82, 247-267

Key Figures

Click the thumbnails to view larger sizes



Climate Data Guide Image: Taylor Diagram NCEP NCAR Reanalysis Taylor Diagram NCEP NCAR Reanalysis

Cite this page

National Center for Atmospheric Research Staff (Eds). Last modified 12 Jun 2022. "The Climate Data Guide: NCEP-NCAR (R1): An Overview." Retrieved from

Acknowledgement of any material taken from this page is appreciated. On behalf of experts who have contributed data, advice, and/or figures, please cite their work as well.