Monthly twelve-digit hydrologic unit code aggregations of the National Hydrologic Model Precipitation-Runoff Modeling System modeling application for Alaska, 1980-2021 (ver. 2.0, February 2026)

This data release contains spatially and temporally summarized simulated variables from the National Hydrologic Model infrastructure with the Precipitation-Runoff Modeling System (NHM-PRMS) modeling application forced with Daymet version 4 for the spatial extent of Alaska (Koczot and others, 2025) from January 1980 through December 2021. Variables are summarized to a monthly time step at a twelve-digit hydrologic unit code spatial resolution for two model-application calibration results: (1) precalibration and (2) byPOIobs. For descriptions of the modeling application calibrations, see Koczot and others (2025). The following estimates of flux and storage are included: total monthly precipitation, evapotranspiration, lateral flow, surface runoff, quickflow, interflow, recharge, groundwater flow, and average monthly snow water equivalent, interflow storage, groundwater storage, total storage, and soil moisture. These data can be found in the NetCDF file, titled “AK_huc12_monthly_nhmprms_daymet_1980_2021.nc” for the precalibration result and "AK_byPOIobs_huc12_monthly_nhmprms_dayment_1980_2021.nc" for the byPOIobs result. In addition to monthly data, two variables at a daily timestep were summarized to a spatial unit of a twelve-digit hydrologic unit code: (1) soil moisture fraction (AK_huc12_daily_soil_moisture_fraction_nhmprms_daymet_1980_2021.nc for the precalibration result and AK_byPOIobs_huc12_daily_soil_moisture_fraction_nhmprms_daymet_1980_2021.nc for the byPOIobs result) and (2) snow water equivalent (AK_huc12_daily_pkwater_equiv_nhmprms_daymet_1980_2021.nc for the precalibration result and AK_byPOIobs_huc12_daily_pkwater_equiv_nhmprms_daymet_1980_2021.nc for the byPOIobs result). Two supplementary files are included that provide the spatial weights or fractions that are used to “weight” model estimates in the area-weighting process (“AK_weights_hru_to_huc12_nhmprms_daymet.csv”) and contain the total fractional area within each twelve-digit hydrologic unit code that is covered by the modeling output ("AK_summed_weights_per_huc12_nhmprms_daymet.csv"). The latter is important for filtering the data where the fractional coverage may be less than one.

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