Skip to main content
U.S. flag

An official website of the United States government

Global Data Assimilation System

The National Center for Environmental Prediction (NCEP) uses the Global Data Assimilation System (GDAS) to interpolate data from a variety of observing systems and instruments onto a three-dimensional grid. NCEI provides access to this gridded output data, which is used to initialize the NCEP Global Forecasting System (GFS) model.

Products

Product Grid/Scale Period of Record Model Cycle Output Timestep Data Access Links
GDAS Snow, Ice, SST, Satellite, Ship, Aircraft (GRIB and BUFR)
  • 1°x1°
  •  0.5°x0.5° 
  • 0.25°x0.25°
01Jan2001–Present (approx. one year to present online)

4/day: 00, 06, 12, 18UTC

Anl, +00, +03, +06, +09 hours HTTPS
GDAS - Daily Tar Files 1°x1° 01Jan2001–21Feb2012

4/day: 00, 06, 12, 18UTC

Anl, +00, +03, +06, +09 hours HAS
GDAS - Hourly Tar Files
  • 1°x1°
  • 0.5°x0.5°
  • 0.25°x0.25°
13Feb2012–Present

4/day: 00, 06, 12, 18UTC

4/day: 00, 06, 12, 18UTC HAS
GDAS - Daily BUFR Files
  • 1°x1°
  • 0.5°x0.5°
  • 0.25°x0.25°
13Feb2012–Present

4/day: 00, 06, 12, 18UTC

Anl, +00, +03, +06, +09 hours HAS

Specifications

Input Data Formats

Due to the variety of assimilated data types, input data are available in several formats, including:

  • Binary Universal Form for the Representation of meteorological data (BUFR)
  • Institute of Electrical and Electronics Engineers (IEEE) binary
Output Data Formats
  • World Meteorological Organization (WMO) Gridded Binary (GRIB)
Observation Types
  • Surface
  • Balloon
  • Wind Profiler
  • Aircraft Reports
  • Buoy
  • Radar
  • Satellite