A Comparison of National Water Model Retrospective Analysis Snow Outputs at Snow Telemetry Sites Across the Western United States

Authors

Irene Garousi-Nejad, Utah State UniversityFollow
David G. Tarboton, Utah State UniversityFollow

Document Type

Article

Author ORCID Identifier

Irene Garousi https://orcid.org/0000-0003-2929-3946

David Tarboton https://orcid.org/0000-0002-1998-3479

Journal/Book Title/Conference

Hyrdrological Processes

Volume

36

Issue

1

Publisher

John Wiley & Sons Ltd.

Publication Date

1-9-2022

Award Number

NSF, Office of Advanced Cyberinfrastructure (OAC) 1664061

Funder

NSF, Office of Advanced Cyberinfrastructure (OAC)

First Page

e14469

Creative Commons License

This work is licensed under a Creative Commons Attribution 4.0 License.

Abstract

This study compares the US National Water Model (NWM) reanalysis snow outputs to observed snow water equivalent (SWE) and snow-covered area fraction (SCAF) at snow telemetry (SNOTEL) sites across the Western United States. SWE was obtained from SNOTEL sites, while SCAF was obtained from moderate resolution imaging spectroradiometer (MODIS) observations at a nominal 500 m grid scale. Retrospective NWM results were at a 1000 m grid scale. We compared results for SNOTEL sites to gridded NWM and MODIS outputs for the grid cells encompassing each SNOTEL site. Differences between modelled and observed SWE were attributed to both model errors, as well as errors in inputs, notably precipitation and temperature. The NWM generally under-predicted SWE, partly due to precipitation input differences. There was also a slight general bias for model input temperature to be cooler than observed, counter to the direction expected to lead to under-modelling of SWE. There was also under-modelling of SWE for a subset of sites where precipitation inputs were good. Furthermore, the NWM generally tends to melt snow early. There was considerable variability between modelled and observed SCAF as well as the binary comparison of snow cover presence that hampered useful interpretation of SCAF comparisons. This is in part due to the shortcomings associated with both model SCAF parameterization and MODIS observations, particularly in vegetated regions. However, when SCAF was aggregated across all sites and years, modelled SCAF tended to be more than observed using MODIS. These differences are regional with generally better SWE and SCAF results in the Central Basin and Range and differences tending to become larger the further away regions are from this region. These findings identify areas where predictions from the NWM involving snow may be better or worse, and suggest opportunities for research directed towards model improvements.

Related Content

• The NWM-R2 are available in the NOAA Google Cloud archive at https://console.cloud.google.com/storage/browser/national-water-model-v2?pli=1. The precipitation and air temperature inputs prepared by the WRF-Hydro NCAR team, we have made available on HydroShare for reproducibility (Garousi-Nejad & Tarboton, 2022f). The NWM elevation dataset was obtained from https://www.nco.ncep.noaa.gov/pmb/codes/nwprod/nwm.v2.0.4/parm/domain/ (accessed November, 30, 2020) and is saved in HydroShare for reproducibility (Garousi-Nejad & Tarboton 2022f).
• The NRCS SNOTEL data are available at https://www.wcc.nrcs.usda.gov/snow/
• The NASA MODIS data are available at https://nsidc.org/data/MOD10A1/versions/6
• The Omernik ecoregions are available at http://www.cec.org/north-american-environmental-atlas/terrestrial-ecoregions-level-iii/

All codes developed for this research are shared and publicly available as a collection on HydroShare (Garousi-Nejad & Tarboton, 2022a) comprised of:

• Input data and code to get the indices of the NWM grid cells containing SNOTEL sites (Garousi-Nejad & Tarboton, 2022d)
• Input data, code to retrieve the NWM-R2 inputs and outputs at SNOTEL sites (Tarboton & Garousi-Nejad, 2022)
• Input data, code and output from post-processing the retrieved NWM-R2 inputs and outputs at SNOTEL sites (Garousi-Nejad & Tarboton, 2022f)
• Input data and code to retrieve precipitation, air temperature, and SWE measurements at SNOTEL sites (Garousi-Nejad & Tarboton, 2022c)
• Input data and Google Earth Engine code to retrieve averaged MODIS-C6 NDSI snow cover at SNOTEL sites (Garousi-Nejad & Tarboton, 2022b)
• Input data, code and output from combining the NWM inputs and outputs with observations form SNOTEL and MODIS at SNOTEL sites (Garousi-Nejad & Tarboton, 2022e)
• Input data, code and output used to produce Figures 1-4 and Figures 6-15 (Garousi-Nejad & Tarboton, 2022g)

Recommended Citation

Garousi-Nejad, I., & Tarboton, D. G. (2022). A comparison of National Water Model retrospective analysis snow outputs at snow telemetry sites across the Western United States. Hydrological Processes, 36( 1), e14469. https://doi.org/10.1002/hyp.14469