Comparison of snow microstructure models Richard Essery Anna Kontu, Samuel Morin, Martin Proksch, Mel Sandells MicroSnow2 Workshop, Columbia MD, 13 – 15 July 2015

Uses of microstructure in snow models Grain size, shape and surface area measures of snow are used in model representations of: thermal conductivity hydraulic permeability compactioncouple to thermodynamics erosion by wind albedo scattering of microwave radiation mechanical stability snow chemistry

Representations of microstructure in snow models Community Land Model (CLM), Oleson et al Crocus, Carmagnola et al Met Office Surface Exchange Scheme (MOSES), Essery et al SNTHERM, Jordan SNOWPACK, Lehning et al Also empirical relationships between SSA and snow type and density Domine et al. (2007). J. Geophys. Res., doi: /2006JF000512

DescriptorsPredictorsProperties Model Grain size Shape Optical radius Bond size Temperature dT/dz Liquid water Density Optical Mechanical Hydraulic Thermal CLM Crocus MOSES SNTHERM Snowpack Microstructure in snow models

Error sources in grain size simulations microstructure process parametrizations parameter values thermodynamics driving data process parametrizations parameter values numerics coupling

Snow model layering

NoSREx FMI ARC, Sodankylä

Snow temperature

Traditional and optical bulk grain sizes correlation 0.58 detrended correlation 0.03

Traditional and optical grain size profiles

Snow temperature profiles

Snow density profiles

Grain size and SSA simulations MOSES r = 0.06 CLM r = 0.41 SNTHERM r = 0.66 MOSES r = 0.32 CLM r = 0.53 SNTHERM r = 0.59 Eulerian layers, simulated snow temperatures

Grain size and SSA simulations CROCUS r = 0.46 MOSES r = 0.35 CLM r = 0.62 SNTHERM r = 0.67 CROCUS r = 0.57 MOSES r = 0.46 CLM r = 0.58 SNTHERM r = 0.60 Lagrangian layers, measured snow temperatures

Tentative conclusions and future directions