The Impact of Initial Snow Conditions on the Numerical Weather Simulation of a Northern Rockies Atmospheric River

Abstract

Snow’s thermal and radiative properties strongly impact the land surface energy balance and thus the atmosphere above it. Land surface snow information is poorly known in mountainous regions. Few studies have examined the impact of initial land surface snow conditions in high resolution, convection permitting numerical weather prediction models during the mid-latitude cool season. The extent to which land surface snow influences atmospheric energy transport and subsequent surface meteorological states is tested using a high resolution (1km) configuration of the Weather Research and Forecasting (WRF) model, for both calm conditions and weather characteristic of a warm late March Atmospheric River. A set of synthetic but realistic snow states are used as initial conditions for the model runs and the resulting differences are compared. We find that snow reduces/increases two meter air temperatures by as much as 4K during both periods, and that the atmosphere responds to snow perturbations through advection of moist static energy from neighboring regions. Snow mass and snow covered area are both important variables that influence two meter air temperature. Finally, the meteorological states produced from the WRF experiments are used to force an offline hydrologic model, demonstrating that snow melt rates can increase/decrease by factor of two depending on the initial snow conditions used in the parent weather model. We propose that more realistic representations of land surface snow properties in mesoscale models may be a source of hydrometeorological predictability

Sensitivities of subgrid-scale physics schemes, meteorological forcing, and topographic radiation in atmosphere-through-bedrock integrated process models: A case study in the Upper Colorado River Basin

“…(2016) and Rudisill et al (2021) implemented a WRF configuration that focused on exploring land-atmosphere interactions in complex terrain. This configuration was developed by researchers at Boise State University, and is referred to as BSU here.…”

“…In terms of land surface process, Jin et al (2010) explored that land surface model complexity improves temperature simulation, but has a minimal impact on simulated precipitation. Additionally, Mallard et al (2017) evaluated that the sensitivity of near-surface temperatures and precipitation to changes in land use representation is smaller than the model error for those fields, while Rudisill et al, (2021) found that the details of snow cover in the initial conditions of a WRF simulation in complex terrain are key to ensuring the skill of that simulation, not just in 2-meter air temperature but also in the surface energy budget.…”

“…Discussion started: 27 June 2022 c Author(s) 2022. CC BY 4.0 License.studies within western US mountain regions(Xu et al, 2018, Rudisill et al 2021). The SWE time-series again shows a similar relationship with precipitation, with the outlier being UCD-ERA5, in terms of the seasonal timing of when snowpack peaks and melts (Figure S-4).…”

SnowClim v1.0: high-resolution snow model and data for the western United States

“…Seasonal snowpack shapes the climatic, hydrologic, ecological, economic, and cultural characteristics of many global regions. Snow is an important determinant of the surface energy balance through its effect on land surface albedo, partitioning of sensible and latent heat fluxes, near-surface atmospheric stability, and horizontal energy transport (Cohen, 1994;Rudisill et al, 2021;Stiegler et al, 2016). Hydrologic benefits of snow include natural water storage, delayed runoff, and cooler stream temperatures (Bales et al, 2006;Luce et al, 2014b).…”

SnowClim v1.0: High-resolution snow model and data for the western United States

“…Snow is an important determinant of the surface energy balance through its effect on land surface albedo, partitioning of sensible and latent heat fluxes, near-surface atmospheric stability, and horizontal energy transport (Cohen, 1994;Rudisill et al, 2021;Stiegler et al, 2016). Hydrologic benefits of snow include natural water storage, delayed runoff, and cooler stream…”