ERA5 / ERA5-Land
Free
ECMWF's hourly global reanalysis — the default gap-free climate forcing record for ungauged catchments worldwide.
MERRA-2
ActiveNASA's satellite-era atmospheric reanalysis — hourly global fields from 1980, the default alternative to ERA5.
by NASA GMAO / GES DISC
- Pricing
- Gov-Public
- License
- US Government (public domain)
- Commercial use
- Permitted
- Ecosystem
- Python, xarray, NetCDF
- Platform
- Windows, macOS, Linux
About MERRA-2
MERRA-2, produced by NASA's Global Modeling and Assimilation Office, is a global atmospheric reanalysis at roughly 0.5°×0.625° resolution and hourly timestep, covering 1980 to near-present, and distributed through GES DISC. It assimilates modern satellite observation types (aerosols, GPS radio occultation) that its predecessor MERRA lacked.
It sits alongside ERA5 as the other reanalysis engineers reach for — coarser in resolution but independent in modelling lineage, which makes it a useful cross-check when a single reanalysis product's biases are a concern.
Where it fits in the workflow
TerrainCatchmentRainfallRunoffRoutingHydraulicsMappingReporting
Alternatives to MERRA-2
Ranked by the topics, categories and workflow stages they share with MERRA-2.
NOAA CFSR / CFSv2
Gov-Public
NCEP's coupled atmosphere-ocean-land reanalysis, sub-daily, 1979–present — strong where ocean coupling matters.
Programmatic access to ERA5 and the Copernicus Climate Data Store — the world's reanalysis workhorse.
The longest satellite soil moisture record available — merged active+passive retrievals back to 1978, free, no login.
Caravan
Open Source
The open global large-sample hydrology dataset — thousands of catchments with forcing, attributes and streamflow.
NetSTORM
Free
CDM Smith's free rainfall statistics and STORM-method screening model — IDF analysis, disaggregation, CSO planning.