Authors: Rachel Corrigan – Colorado School of Mines
Title: Assessing the effects of uncertainty in windspeed and precipitation forcings on lateral snow redistribution in mountainous basins
Presentation Type: Poster Presentation
Abstract: Snow-dominated montane watersheds provide ecological services, water storage, and water supply for downstream population centers across the globe. Mountain snowpack predictions are critical for water supply forecasting in these regions. Recent literature suggests that hydrologic model uncertainty in mountain watersheds is largely driven by meteorological forcing uncertainty. Additionally, relatively few spatially distributed models simulate lateral snow transport processes such as blowing snow and avalanching, meaning that the impact of forcing uncertainty in the context of snowpack redistribution is under-explored. Here, we ask how uncertainty in windspeed and precipitation forcing affects modeled lateral redistribution of snow in mountain basins. We hypothesize that windspeeds and precipitation from downscaled meteorological datasets require numerical correction for effective snow redistribution, and that the magnitude of these corrections will vary across geographic regions.We use the Canadian Hydrologic Model (CHM) to simulate snow accumulation several water years within a set of basins in the Sierra Nevada and Rocky Mountains in the US that have extensive airborne lidar observations from the Airborne Snow Observatory (ASO).
We use two climate forcing datasets with different underlying resolutions to evaluate the effects of windspeed and precipitation resolution on modeled snowpack in mountainous terrain. We use observed in situ and airborne lidar-based SWE, fractional snow-covered area, and derived snow disappearance date from SNOTEL, snow courses, the Airborne Snow Observatory, and MODSCAG to evaluate model results using a standardized benchmarking process. This enables us to decipher whether corrections to windspeed and precipitation yield similar metrics despite different underlying redistribution processes, and whether these adjustments improve spatial distribution of snow-water equivalent in model simulations. We assess whether these adjustments are geographically transferable across mountain basins in the US or are region-specific. Our results can provide guidance for improving snowpack simulations across mountainous terrain and contribute to streamflow forecasting in snowmelt dominated watershed. .