Abstract. Seasonal snow is an essential component of regional and global
water and energy cycles, particularly in snow-dominant regions that rely on
snowmelt for water resources. Land surface models (LSMs) are a common
approach for developing spatially and temporally complete estimates of snow
water equivalent (SWE) and hydrologic variables at a large scale. However,
the accuracy of the LSM-based SWE outputs is limited and unclear by mixed
factors such as uncertainties in the meteorological boundary conditions and
the model physics. In this study, we assess the SWE, snowfall,
precipitation, and air temperature products from a 12-member ensemble –
with four LSMs and three meteorological forcings – using automated SWE,
precipitation, and temperature observations from 809 Snowpack Telemetry
stations over the western US. Results show that the mean annual maximum LSM
SWE is underestimated by 268 mm. The timing of peak SWE from the LSMs is on average 36 d earlier than that of the observations. By the date of peak
SWE, winter accumulated precipitation is underestimated (forcings mean: 485
mm vs. stations: 690 mm). In addition, the precipitation partitioning
physics generates different snowfall estimates by an average of 113 mm with the same forcing data. Even though there are widespread cold biases (up to 3 ∘C) in the temperature forcings, larger ablations and lower ratios of SWE to total precipitation are found even in the accumulation period, indicating that melting physics in LSMs drives some SWE uncertainties. Based on the principal component analysis, we find that
precipitation bias and partitioning methods have a large contribution to the first principal component, which accounts for about half of the total
variance. The results provide insights into prioritizing strategies to
improve SWE estimates from LSMs for hydrologic applications.
