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Entry · Data sources

IMERG: Satellite-estimated precipitation (IMERG)

Where does the satellite rainfall estimate come from?

● checked against the primary source on Oct 1, 2026Source: NASA

Acronyms: EAR, Stored Energy.

In one sentence

Rainfall estimate from NASA's GPM mission, which combines several satellites on a 0.1° grid (about 10 km), with a quick version (Late) and a final one, published about 3.5 months later.

Real example

30-day rainfall in the PARANAIBA basin

70 mmNature of the data: Estimated

Aug 16, 2026 to Sep 14, 2026 · PARANAIBA basin (largest maximum EAR)

Source: NASA, POWER Daily API (total precipitation (IMERG)), agregado pela Scrutiniums. Reference up to Sep 14, 2026. Captured on Sep 30, 2026. Dataset code at the source: IMERG_PRECTOT.

Rainfall accumulated over 30 days in the basin with the largest maximum EAR, estimated by IMERG.

See in the panel: Water and climate: rainfall and temperature

Estimated: Value obtained by a statistical procedure, with uncertainty.

Why it matters

Without a station in every basin, the average rainfall of a river basin can only be estimated from a grid; it is the input the observatory uses for rainfall by basin.

How it is measured

Daily precipitation (UTC day) at each grid point, read through the NASA POWER service; the Late version arrives in about 14 hours and is replaced by the Final one.

Unit: mm of precipitation per day

Not to be confused with

What cannot be concluded

  • It is an estimate, not a station measurement; the Late version lacks the rain gauge calibration of the Final one.
  • In POWER, IMERG only exists by day and in UTC time.

Related entries

Official source

  • NASA (Langley Research Center), projeto POWERPOWER Docs, Methodology, Data Sources (Precipitation section) 

    In other words: POWER rainfall comes from IMERG, the multi-satellite product of NASA's GPM mission, on a global grid of 0.1° by 0.1° (about 10 km). On the same page, the sources table says the Final version starts on Jan 1, 2001 and arrives 3.5 months behind real time, and the Late version covers the period after it, with a delay of about 14 hours.

    Literal excerpt from the document
    “POWER's higher resolution precipitation data is derived from NASA's Global Precipitation Measurement (GPM) mission's Integrated Multi-satellitE Retrievals for GPM (IMERG). The resolution of the IMERG precipitation data is a global 0.1° latitude by 0.1° longitude grid (approximately 10 km).”

Documents accessed and text checked on Oct 1, 2026.