A Multifaceted Evaluation of National Water Model Snow Processes in Complex Terrain

Snow accumulation and melting processes strongly influence both water resources management at the seasonal scale and streamflow formation at the event scale. Despite this fundamental importance at both seasonal and weather time scales, the representation and evaluation of snow from atmospheric forcings to hydrological processes represent a challenging task. The challenges arise due to both sparse observations in complex topography areas (where most seasonally persistent snowpack exists in the Contiguous US) as well as models struggling to parametrize complex land-surface snow processes.
The goal of this work is to understand how snow processes are represented by the National Water Model, using different evaluation techniques and applying experiments to investigate different components of the model (from forcing inputs to model outputs). Experiment objectives include a better understanding of how solid and mixed precipitation partitioning impacts NWM land surface model (Noah-MP) snowpack evolution during mixed-phase weather events as well as understanding snow accumulation and melting processes on seasonal timescales. The experiments are designed to evaluate both streamflow as well as snow fields. The analysis uses a range of tools at different scales, from single-column Noah-MP model experiments to watersheds and CONUS-scale verification.
The outcome of this study will be applied to guide future improvements in NWM forcings, NWM physical processes inside the land surface model and to develop snow data-assimilation techniques to possibly improve NWM prediction.