TRMM_3B31: Combined Radar-Radiometer Monthly Precipitation

TRMM_3B31 provides monthly, 0.5-degree gridded precipitation data by calibrating wide-swath radiometer retrievals with high-quality, narrow-swath radar data. This combined product from the Tropical Rainfall Measuring Mission (TRMM) satellite is preserved in HDF4 format, with newer versions available in GPM's HDF5 format. The algorithm calculates monthly adjustment ratios for each vertical layer within the satellite swath overlap region, filtering out sea ice.

Use Cases

• Calibrating satellite precipitation algorithms based on the described radar-radiometer adjustment method.
• Analyzing monthly precipitation climatologies at a 0.5-degree spatial resolution.
• Studying vertical profiles of precipitation and cloud microphysics in tropical and subtropical regions.
• Validating numerical weather prediction models using a long-term, satellite-derived precipitation record.

Strengths

• Provides a calibrated, combined product leveraging both radar and radiometer sensors from TRMM.
• Features a permanent preservation state, indicating long-term archival stability.
• Spatial resolution is explicitly defined as 0.5 degree x 0.5 degree.

Limitations

• Metadata completeness is low: column names, row counts, and exact temporal coverage are unknown.
• The dataset is in a legacy HDF4 format, with newer GPM HDF5 versions recommended for use.
• Conflicting 'last updated' dates exist between sources (2026 vs. 2015), creating uncertainty about provenance.

Provenance

Source

National Aeronautics and Space Administration (NASA)

Collection Method

Satellite remote sensing from the Tropical Rainfall Measuring Mission (TRMM).

Freshness

2026-04-09 21:39:23.304306 (from datagov, though this appears to be a future date which may be an error)

Geography

Likely global, focusing on tropical and subtropical regions covered by TRMM.