Hourly Global Radiation Diagnostics from NASA MERRA-2 Reanalysis

MERRA-2 provides hourly time-averaged radiation diagnostics, including surface albedo, cloud area fraction, and top-of-atmosphere longwave flux. NASA's Global Modeling and Assimilation Office produced this reanalysis using the GEOS model version 5.12.4. The dataset covers the period from 1980 to the present, with data time-stamped at the central hour (e.g., 00:30 UTC).

Use Cases

• Analyze trends in surface incoming shortwave flux (solar radiation) and surface net downward shortwave flux to study changes in surface energy absorption.
• Model cloud radiative effects by correlating cloud area fraction and in-cloud optical thickness with outgoing longwave radiation at the top of the atmosphere.
• Validate climate model simulations of surface albedo against this reanalysis product across different geographic regions.
• Assimilate upwelling longwave flux at the top of the atmosphere observations to constrain atmospheric reanalysis models.

Strengths

• Data coverage spans from 1980 to present, providing over 40 years of continuous hourly observations.
• Produced by NASA's Global Modeling and Assimilation Office using the authoritative GEOS model, ensuring a consistent, physically-based record.
• Provides multiple key radiation diagnostics, including surface albedo and cloud area fraction, in a single collection.

Limitations

• Spatial resolution is 0.625 x 0.5 degrees, which may be too coarse for regional or local-scale studies.
• Data has a latency of approximately three weeks after the end of a month, limiting real-time applications.
• As a model reanalysis product, the data represents a best-estimate blend of observations and model physics, not direct measurements.

Provenance

Source

NASA Global Modeling and Assimilation Office (GMAO) via the Goddard Earth Sciences Data and Information Services Center (GES DISC).

Collection Method

Generated by the Goddard Earth Observing System Model (GEOS) version 5.12.4, assimilating satellite and observational data.

Time Range

1980 to present.

Freshness

Updated monthly with a ~3-week latency.

Geography

Global coverage at 0.625 x 0.5 degree resolution.