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.

Version History Summary:
First Published: May 2025
Version 2.0: January 2026

本数据集发布内容包含基于搭载降水-径流模拟系统（Precipitation-Runoff Modeling System, PRMS）的国家水文模型基础设施（National Hydrologic Model infrastructure）所生成的时空聚合模拟变量，该NHM-PRMS模拟应用以Daymet第4版数据作为强迫驱动场，空间覆盖阿拉斯加地区（Koczot等，2025），时间跨度为1980年1月至2021年12月。所有变量以12位水文单元代码（twelve-digit hydrologic unit code, HUC12）作为空间分辨率，按月时间步长进行聚合，对应两组模型应用校准结果：(1) 预校准（precalibration）结果；(2) byPOIobs校准结果。关于模型应用校准的详细说明，请参见Koczot等（2025）。本次发布包含以下通量与蓄水量估算结果：月均总降水量、蒸散发、侧向流、地表径流、快速流、壤中流、补给量、地下水径流，以及月均雪水当量、壤中流蓄水量、地下水蓄水量、总蓄水量与土壤含水量。上述数据分别存储于NetCDF格式文件中，预校准结果对应文件为"AK_huc12_monthly_nhmprms_daymet_1980_2021.nc"，byPOIobs校准结果对应文件为"AK_byPOIobs_huc12_monthly_nhmprms_dayment_1980_2021.nc"。除月尺度数据外，另有两组日尺度变量被聚合至12位水文单元空间尺度，分别为：(1) 土壤水分占比：预校准结果对应文件为"AK_huc12_daily_soil_moisture_fraction_nhmprms_daymet_1980_2021.nc"，byPOIobs校准结果对应文件为"AK_byPOIobs_huc12_daily_soil_moisture_fraction_nhmprms_daymet_1980_2021.nc"；(2) 雪水当量：预校准结果对应文件为"AK_huc12_daily_pkwater_equiv_nhmprms_daymet_1980_2021.nc"，byPOIobs校准结果对应文件为"AK_byPOIobs_huc12_daily_pkwater_equiv_nhmprms_daymet_1980_2021.nc"。本数据集还包含两份辅助文件：其一为"AK_weights_hru_to_huc12_nhmprms_daymet.csv"，存储了面积加权过程中用于对模型估算结果进行加权的空间权重或占比数据；其二为"AK_summed_weights_per_huc12_nhmprms_daymet.csv"，记录了每个12位水文单元内被模型输出覆盖的总面积占比，该信息可用于筛选覆盖占比不为1的数据集条目。版本历史摘要：首次发布：2025年5月；2.0版本：2026年1月