Journal Article

Snowdrift‐Permitting Simulations of Seasonal Snowpack Processes Over Large Mountain Extents

Marsh, Christopher B., Lv, Zhibang, Vionnet, Vincent, Pomeroy, John W., Spiteri, Raymond J., Harder, Phillip

2024

Overview

The melt of seasonal snowpack in mountain regions provides downstream river basins with a critical supply of freshwater. Snowdrift‐permitting models have been proposed as a way to accurately simulate snowpack heterogeneity that stems from differences in energy inputs, over winter redistribution, sublimation, melt, and variations in precipitation. However, these spatial scales can be computationally intractable for large extents. In this work, the multiscale Canadian Hydrological Model (CHM) was applied to simulate snowpacks at snowdrift‐permitting scales (≈50 m) across the Canadian Cordillera and adjacent regions (1.37 million km2) forced by downscaled atmospheric data. The use of a multiscale land surface representation resulted in a reduction of computational elements of 98% while preserving land‐surface heterogeneity. CHM includes complex terrain windflow and radiative transfer calculations, lapses temperature, humidity, and precipitation with elevation, redistributes snow by avalanching, wind transport and forest canopy interception and calculates the energetics of canopy and surface snowpacks. Model outputs were compared to a set of multiscale observations including snow‐covered area (SCA) from Sentinel and Landsat imagery, snow depth from uncrewed aerial system lidar, and point surface observations of depth and density. Including snow redistribution and sublimation processes improved the summer SCA r2 from 0.7 to 0.9. At larger scales, inclusion of snow redistribution processes delayed full snowpack ablation by an average of 33 days, demonstrating process emergence with scale. These simulations show how multiscale modeling can improve snowpack predictions to support prediction of water supply, droughts, and floods. Plain Language Summary The spring melting of snowpacks in mountainous regions is crucial for providing freshwater to downstream river basins. Accurate simulation of mountain snowpacks requires accounting for factors like energy input, redistribution of snow, and forest canopies. However, including all these factors can be computationally challenging for large areas. In this study, the Canadian Hydrological Model (CHM) was used to simulate snowpacks at fine scales (about 50 m) across the Canadian Cordillera and nearby regions. By using a multiscale approach, the computational requirements were reduced substantially while maintaining the range of landscape features. The CHM accounts for various factors such as windflow, mountain shadowing, temperature, humidity, and precipitation changes with elevation, as well as snow redistribution through avalanching and wind transport. The model was validated against multiscale observations including satellite imagery, lidar data, and point observations. By incorporating snow redistribution and sublimation processes in the model, the accuracy of snow cover predictions improved over spring and summer. At larger scales, considering snow redistribution delayed the complete melting of snowpacks by an average of 33 days, showcasing the importance of scale‐dependent redistribution and ablation processes. These simulations demonstrate how multiscale modeling enhances snowpack predictions, aiding in forecasts of water supply, droughts, and floods. Key Points A novel, large extent, snowdrift permitting scale simulation of ≈1.4 M km2 was performed The inclusion of snow redistribution was scale emergent and delayed full snowcover ablation by 33 days on average The inclusion of snow redistribution processes improved the summer simulated versus observed snow‐covered area r2 from 0.7 to 0.9

• Publisher: John Wiley & Sons, Inc,Wiley
• Subject: Ablation / Atmospheric data / Canopies / Canopy / Computer applications / Downstream / Drought / Elevation / Flood forecasting / Flood predictions / Floods / forest canopy / Freshwater / Heterogeneity / Humidity / Hydrologic models / Hydrologic studies / Hydrology / Inland water environment / Interception / Landsat / landscapes / Lidar / Melting / Modelling / Mountain regions / Mountain snow / Mountains / Multiscale analysis / Plant cover / Precipitation / Precipitation variations / prediction / Predictions / Radiative transfer / Remote sensing / River basins / Rivers / Satellite imagery / Satellite observation / SCA / seasonal snowpacks / Simulation / Snow / Snow cover / Snow depth / Snowdrifts / snowdrift‐permitting simulations / Snowpack / Spring / Spring (season) / Sublimation / Summer / temperature / Temperature requirements / water interception / Water supply / Wind / Wind transport