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Entry · Data sources

MERRA-2: MERRA-2 reanalysis (estimated temperature)

Where does the estimated temperature used by the panels come from?

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

Acronyms: SIN, National Interconnected System.

In one sentence

NASA reanalysis: a model of the GEOS data assimilation system that reconstructs past weather on a 0.5° by 0.625° grid; the most recent days come from GEOS-IT until MERRA-2 replaces them.

Real example

SIN temperature anomaly over 30 days

+0.1 °CNature of the data: Estimated

Aug 29, 2026 to Sep 27, 2026 · SIN (27 states, weighted by population)

Source: NASA, POWER Daily API (T2M), agregado pela Scrutiniums. Reference up to Sep 27, 2026. Captured on Sep 30, 2026.

SIN temperature anomaly over 30 days compared with the same window from 2001 to 2025, with the reanalysis cells and the states weighted by population.

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

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

Why it matters

It gives the temperature of any point in the country with the same rule since 1981, which allows comparing a period with the average of many years; the observatory uses the temperature of the most populated areas of each state.

How it is measured

Air temperature at 2 meters, daily mean, maximum and minimum, by grid cell, read through the NASA POWER service.

Unit: °C (air temperature at 2 meters)

Not to be confused with

What cannot be concluded

  • It is a model estimate, not a station measurement; the check against INMET stations was not done (INMET did not respond in the collection attempts).
  • The end of the series comes from GEOS-IT and changes when MERRA-2 arrives.

Related entries

See in the panel

Official source

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

    In other words: POWER's meteorological variables come from the MERRA-2 assimilation model, a version of NASA's GEOS system, and from GEOS-IT, which has the same grid. GEOS-IT is processed every day and appended to the end of the MERRA-2 series to provide data with a delay of about two days; the MERRA-2 values in the series are usually updated every few months. The meteorological grid is ½° latitude by ⅝° longitude, and the sources table on the same page says MERRA-2 starts on Jan 1, 1981.

    Literal excerpt from the document
    “the meteorological data source is ½° latitude by ⅝° longitude grid from GMAO MERRA-2. [...] Meteorological parameters are derived from NASA's GMAO MERRA-2 assimilation model and GEOS-IT. MERRA-2 is a version of NASA's Goddard Earth Observing System (GEOS) Data Assimilation System (Bosilovich, M. G., et al., 2016). GEOS-IT has the same grid resolution as MERRA-2 (and the same model physics less selected observations and surface rain gauge normalized precipitation). The POWER team processes GEOS-IT data on a daily basis, and it is appended to the end of the MERRA-2 daily time series to provide low latency products, which are generally ready within about two days of real-time. The MERRA-2 values in the resulting daily time series are typically updated every several months.”

Documents accessed and text checked on Oct 1, 2026.