National Aeronautics and Space Administration

NOTE: MERRA production has been discontiued with the completion of analyses through February 29, 2016.
MERRA-2 is now available.

MERRA-Land is a land-only ("off-line") replay of the MERRA land model component with two key changes from MERRA:

1. MERRA-Land precipitation forcing is based on merging a gauge-based data product from the NOAA Climate Prediction Center with MERRA precipitation.
2. The Catchment land surface model used in MERRA-Land was updated from the "MERRA" version (used in GEOS-5.2.0) to the "Fortuna-2.5" version (used operationally in GEOS-5.7.2 since Aug 2011).

These two changes lead to various science improvements that are documented, for a preliminary version of the MERRA-Land data product, in Reichle et al. (2011) and, for the official MERRA-Land data product, in the MERRA-Land documentation.

With a few exceptions, the MERRA-Land data appear more accurate than the original MERRA estimates and are thus recommended for those interested in using MERRA output for land surface hydrological studies. As an example, Figure 1 examines the drought conditions experienced across the western United States and along the East Coast during August 2002. The figure clearly demonstrates that MERRA-Land data are more consistent with the Drought Monitor than MERRA data.

Figure 1: Drought indicator derived from (top left) MERRA and (bottom left) MERRA-Land root zone soil moisture estimates for August 2002. Darker colors indicate more severe drought conditions. MERRA-Land estimates are more consistent than MERRA estimates with an independent drought assessment from the US Drought Monitor for 13 August 2002. The MERRA and MERRA-Land drought indicator is derived by ranking, separately for each grid cell, the normalized, monthly mean root zone soil moisture anomalies for June, July, and August of 1980 through 2011 and converting the rank for August 2002 into percentile units.

See MERRA-Land Data Access for information on requesting the data.

See also MERRA-Land References.