Nicolas R. Leroux, Vincent Vionnet,Julie M. Thériault, Hadleigh D. Thompson, Dominique Boisvert, Lisa Rickard, Stephen J. Déry, Ronald Stewart (2022). Impact of different precipitation phase estimation methods around 0oC on snowpack evolution. . Proceedings of the GWF Annual Open Science Meeting, May 16-18, 2022.

Accurate estimation of precipitation phase at the surface is critical for hydrological modelling in cold regions. The current precipitation phase partioning methods (PPM) differ in their abilities to estimate precipitation phase around 0oC. This can have significant impacts on estimations of snow accumulation and melt, particularly as the climate is warming and near 0oC conditions become more frequent during the cold seasons (Mekis et al., 2020). The goal of this study is to evaluate PPMs of varying complexity using high-quality observations of precipitation phase and to assess the impact on simulated snowpack evolution over a winter season. To do so, we used meteorological data including air temperature, relative humidity, wind speed, and precipitation amount collected at Edmundston, New Brunswick, during the Saint John River Experiment on Cold Season Storms field campaign. These data were combined with observations of snow depth and snow water equivalent. The reference precipitation phase was derived from measurements with a laser-optical disdrometer operating during SAJESS and was evaluated using Doppler velocity and reflectivity measurements from a micro rain radar. The snowpack evolution during the 2020-2021 winter was simulated using the model Crocus. The impact of the different PPMs on snow depth estimation during 16 accumulation periods across the winter season, as well as uncertainties related to compaction and snowfall density models was investigated. The results show that the snow accumulation from the different PPMs differed significantly when the temperature was close to 0oC and that precipitation phase estimated from disdrometer data was the most accurate when simulating snow accumulation, followed by the PPM using the wet-bulb temperature with a constant threshold. Snow events accumulation were more sensitive to the snowfall density model chosen than to the compaction algorithm. However, the impact of the snowfall density models on snow accumulation was insensitive to the PPM chosen, while the performance of the compaction models was slightly influenced by the selected PPM. Overall, this study highlights the difficulty in estimating precipitation phase at the surface during near 0oC conditions and its impact on snow modelling.

Mekis, E., Stewart, R. E., Theriault, J. M., Kochtubajda, B., Bonsal, B. R., & Liu, Z. (2020). Near-0°C surface temperature and precipitation type patterns across Canada. Hydrology and Earth System Sciences, 24(4), 1741–1761. https://doi.org/10.5194/hess-24-1741-2020

AOSM2022 SAJESS First Author: Nicolas R. Leroux, UQAM Additional Authors: Vincent Vionnet, ECCC; Julie M. Thériault, UQAM; Hadleigh D. Thompson, UQAM; Dominique Boisvert, UQAM; Lisa Rickard, UNBC; Stephen J. Déry, UNBC; Ronald Stewart, University of Manitoba