NLDAS-2¶

North American Land Data Assimilation System Phase 2 (NLDAS-2 — 0.125° hourly forcing and Noah, Mosaic and VIC land surface model output)

Available

At a glance¶

Note on period: Hourly forcing (FORA, FORB) starts at 13Z on 1979-01-01 and model output (Noah, Mosaic, VIC) around 00Z on 1979-01-02 (01Z for Noah and 00Z for Mosaic and VIC in CMR). Monthly files start in 1979-01 and the monthly climatology (MC) is a 40-year 1981–2020 average. On 2026-10-13 hourly Noah reached 2026-10-08 23Z, FORA 2026-10-09 12Z and the monthly files 2026-09.

Overview¶

NLDAS-2 is a land dataset for the conterminous US and surroundings run jointly by NASA, NOAA and partners. It provides 0.125° hourly forcing built from observation-based precipitation (CPC daily gauge analysis disaggregated with radar) and NARR meteorology, together with soil moisture, evapotranspiration, runoff, snow and energy fluxes from the Noah, Mosaic and VIC land surface models driven by that forcing, from 1979 onward. Despite the name, it is an open-loop simulation without data assimilation, and the forcing alone is widely used to drive other hydrological models. It is widely used for drought monitoring and hydrological research, and a successor, NLDAS-3 (1 km, North and Central America), is under development.

What changes with the successor¶

NLDAS-2 GRIB-1 (V002) → NLDAS-2 netCDF (V2.0)¶

Transition: 2024-08

V2.0, the same NLDAS-2 data rewritten as CF/ALMA-convention netCDF, was released in 2020–2021, and the GRIB-1 version (V002) stopped updating with data valid at 23Z on 1 August 2024.

Sources: NLDAS-2 GRIB-1 files no longer updated as of 1 August 2024 (NASA LDAS) · NLDAS-2 README (netCDF V2.0)

NLDAS-2 → NLDAS-3 Planned¶

NASA's third-phase NLDAS raises the resolution to 1 km, extends the domain to all of North and Central America, and moves to the Noah-MP model with satellite data assimilation. On 2026-10-13 only beta forcing for 2001–2023 was public on AWS; model output, announced as 'expected mid-2026', had not yet appeared. NLDAS-3 is not registered at GES DISC or in CMR.

Sources: NASA LDAS — NLDAS-3 · NLDAS-3 GitHub (NASAWaterInsight) · NLDAS-3 Drought Workshop 3 Slides (2025-04-10)

Available variables¶

Main variables from the NLDAS-2 netCDF (V2.0) README tables (Tables 3 and 6) and GES DISC files (NLDAS_FORA0125_H, NLDAS_NOAH0125_M). Names are ALMA-convention netCDF names and differ from the GRIB-1 PDS-number names. Mosaic and VIC output use the same naming pattern and differ only in the soil variables (VIC uses SoilM_layer1 to 3, etc.). The optional secondary forcing FORB holds NARR precipitation, NARR hybrid-level temperature, humidity, pressure and wind with their height, aerodynamic conductance and more (see the README for the list).

instantaneous mean accumulated maximum minimum static — instantaneous: value at the time stamp · mean/accumulated/maximum/minimum: over the indicated interval · static: does not change with time

Primary forcing FORA (hourly, instantaneous at the top of the hour)¶

Primary forcing FORA (hourly, total over the previous hour)¶

Noah output — energy fluxes (hourly, previous-hour mean)¶

Noah output — water fluxes (hourly, previous-hour total)¶

Noah output — states (hourly, instantaneous at the top of the hour)¶

Monthly files (NLDAS_*0125_M)¶

The full variable list is in the official documentation.

How to get the data¶

• NASA GES DISC — NLDAS dataset list — HTTPS download / earthaccess / Earthdata Search / OPeNDAP / subsetting
  • Short names are NLDAS_0125_, version 2.0 (file names end in .020.nc). The GRIB-1 version (V002) has not been updated since 2024-08-01. SAC model output is not at GES DISC; it is only on the NOAA NCEP/EMC NLDAS website. A free Earthdata Login is required, and the old server (hydro1.gesdisc.eosdis.nasa.gov) may close after 30 September 2026, so switch to data.gesdisc.earthdata.nasa.gov or earthaccess.
• AWS us-west-2 direct access (S3) — Cloud storage (S3, in-region us-west-2 only)
  • Example: s3://gesdisc-cumulus-prod-protected/NLDAS/NLDAS_FORA0125_H.2.0/ — temporary credentials are required.
• NASA Giovanni — Web maps and time series; NetCDF, GeoTIFF and KMZ downloads
  • Quick area-mean time series.
• NASA LDAS — NLDAS — Documentation, FAQ and news
  • Forcing configuration, known issues, reprocessing notices and NLDAS-3 development news.

Example code¶

Uses earthaccess to download the FORA hourly files for 1 July 2023 and build the 00–24Z daily precipitation (mm). Because the 03Z file holds the 02–03Z total, the 24 files from 01Z that day to 00Z the next day are used. You will be asked for your Earthdata credentials on the first run.

import earthaccess
import xarray as xr

earthaccess.login()  # free NASA Earthdata account
results = earthaccess.search_data(
    short_name="NLDAS_FORA0125_H", version="2.0",
    temporal=("2023-07-01T01:00:00", "2023-07-02T00:00:00"),   # files 01Z to next-day 00Z = 00-24Z totals
    bounding_box=(-125, 25, -67, 53),
)
files = earthaccess.download(results, "nldas_fora_h")

ds = xr.open_mfdataset(files, combine="by_coords")
print(ds.time.values)                     # check there are 24 time steps
daily_precip = ds["Rainf"].sum("time")    # kg m-2 = mm, 2023-07-01 00-24Z
tmax = ds["Tair"].max("time") - 273.15    # highest of the hourly instantaneous values (deg C)
print(float(daily_precip.mean()), float(tmax.mean()))

Practical tips¶

• SWdown and LWdown are instantaneous in the FORA forcing but previous-hour means in the Noah output files. Check which file you use when computing daily mean radiation.
• Hourly Rainf is a previous-hour total (kg m-2 = mm), not a rate. Sum the 01Z to next-day 00Z files for a daily total; monthly Rainf is already the monthly total, so do not multiply by the number of days again.
• From August 2022 to 1 March 2024, an error in the NCEP R-CDAS snow-depth input made temperatures too warm, so snow, runoff and soil moisture (especially in winter 2022–23) were wrong; the period was reprocessed on 7 June 2024. Re-download any data for this period obtained before then.
• Known issues: unrealistic precipitation on the Canadian side of the US–Canada border in many years; isolated very dry spots from gauge quality-control problems; and a change in precipitation behaviour from 1 January 2012 due to a new interpolation algorithm, notably along the US–Mexico border, in western mountains and along coastlines. The README states these cannot be fixed by regenerating the data at this time.
• Mosaic output: the four evaporation fluxes had reversed signs in the GRIB files (corrected in netCDF), and canopy conductance has been incorrectly defined since 01Z on 2008-03-09, which carries over to netCDF.
• Noah soil moisture such as SoilM_0_100cm is in kg m-2 (mm). Divide by the layer thickness in mm to get volumetric water content.
• The old GRIB-1 version (V002) uses different variable names from netCDF V2.0 and has not been updated since 23Z on 2024-08-01. On 2026-10-13 no V002 collections appeared in NASA CMR, so move scripts to V2.0.
• The monthly climatology (MC) in the netCDF version averages 1981–2020 (40 years; the old GRIB version used 1980–2009). State the baseline when computing anomalies.

Notices and change history¶

References for your paper¶

Dataset citation¶

NLDAS-2 Noah hourly V2.0 (GES DISC) — DOI 10.5067/T4OW83T8EXDO

@misc{nldas2_noah0125_h,
  author    = {{NLDAS project}},
  editor    = {Mocko, David},
  title     = {{NLDAS} Noah Land Surface Model {L4} Hourly 0.125 x 0.125 degree {V2.0}},
  year      = {2020},
  publisher = {Goddard Earth Sciences Data and Information Services Center (GES DISC)},
  address   = {Greenbelt, MD, USA},
  doi       = {10.5067/T4OW83T8EXDO}
}

NLDAS-2 primary forcing (FORA) hourly V2.0 (GES DISC) — DOI 10.5067/THUF4J1RLSYG

@misc{nldas2_fora0125_h,
  author    = {{NLDAS project}},
  editor    = {Mocko, David},
  title     = {{NLDAS} Primary Forcing Data {L4} Hourly 0.125 x 0.125 degree {V2.0}},
  year      = {2020},
  publisher = {Goddard Earth Sciences Data and Information Services Center (GES DISC)},
  address   = {Greenbelt, MD, USA},
  doi       = {10.5067/THUF4J1RLSYG}
}

NLDAS-2 Noah monthly V2.0 (GES DISC) — DOI 10.5067/WB224IA3PVOJ

@misc{nldas2_noah0125_m,
  author    = {{NLDAS project}},
  editor    = {Mocko, David},
  title     = {{NLDAS} Noah Land Surface Model {L4} Monthly 0.125 x 0.125 degree {V2.0}},
  year      = {2020},
  publisher = {Goddard Earth Sciences Data and Information Services Center (GES DISC)},
  address   = {Greenbelt, MD, USA},
  doi       = {10.5067/WB224IA3PVOJ}
}

Reference papers¶

NLDAS-2 configuration and model intercomparison (Xia et al. 2012a) — DOI 10.1029/2011JD016048

@article{xia2012nldas2,
  author  = {Xia, Youlong and Mitchell, Kenneth and Ek, Michael and Sheffield, Justin and Cosgrove, Brian and Wood, Eric F. and Luo, Lifeng and Alonge, Charles and Wei, Helin and Meng, Jesse and Livneh, Ben and Lettenmaier, Dennis and Koren, Victor and Duan, Qingyun and Mo, Kingtse and Fan, Yun and Mocko, David},
  title   = {Continental-scale water and energy flux analysis and validation for the {North American Land Data Assimilation System} project phase 2 ({NLDAS-2}): 1. Intercomparison and application of model products},
  journal = {Journal of Geophysical Research},
  volume  = {117},
  number  = {D3},
  pages   = {D03109},
  year    = {2012},
  doi     = {10.1029/2011JD016048}
}

NLDAS project background (Mitchell et al. 2004) — DOI 10.1029/2003JD003823

@article{mitchell2004nldas,
  author  = {Mitchell, Kenneth E. and Lohmann, Dag and Houser, Paul R. and Wood, Eric F. and Schaake, John C. and Robock, Alan and Cosgrove, Brian A. and Sheffield, Justin and Duan, Qingyun and Luo, Lifeng and Higgins, R. Wayne and Pinker, Rachel T. and Tarpley, J. Dan and Lettenmaier, Dennis P. and Marshall, Curtis H. and Entin, Jared K. and Pan, Ming and Shi, Wei and Koren, Victor and Meng, Jesse and Ramsay, Bruce H. and Bailey, Andrew A.},
  title   = {The multi-institution {North American Land Data Assimilation System} ({NLDAS}): Utilizing multiple {GCIP} products and partners in a continental distributed hydrological modeling system},
  journal = {Journal of Geophysical Research: Atmospheres},
  volume  = {109},
  number  = {D7},
  year    = {2004},
  doi     = {10.1029/2003JD003823}
}

Acknowledgements¶

Cite the DOI of each product you use; the others are tabulated in the README (e.g. FORA monthly 10.5067/2DPKB5B5N14O, FORB hourly 10.5067/96S0R3LFOBTU, Mosaic hourly 10.5067/TS58ZCJZIWT5, VIC hourly 10.5067/45T7K120BJ2S). NASA asks that publications include: "The data used in this study were acquired as part of the mission of NASA's Earth Science Division and archived and distributed by the Goddard Earth Sciences (GES) Data and Information Services Center (DISC)." The README recommends Mitchell et al. (2004) for project background and Xia et al. (2012a, 2012b) for the NLDAS-2 configuration.

Information on the datasets used in this study was compiled with the help of the Korean Climate Data Navigator (KCDN) (Sim, 2026; https://doi.org/10.5281/zenodo.23300923).

Links¶

• NASA LDAS — NLDAS
• NLDAS-2 README (netCDF V2.0 variable tables, time conventions, DOI table)
• NLDAS FAQ
• NLDAS-2 reprocessing summary (2022-08 to 2024-03)
• GES DISC NLDAS_NOAH0125_H 2.0
• NASA LDAS — NLDAS-3