Comparison of snow microstructure models Richard Essery Anna

Comparison of snow microstructure models Richard Essery Anna Kontu, Samuel Morin, Martin Proksch, Mel Sandells Micro. Snow 2 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 • compaction couple 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. 2010 www. cesm. ucar. edu/models/ccsm 4. 0/clm/CLM 4_Tech_Note. pdf Crocus, Carmagnola et al. 2014 www. the-cryosphere. net/8/417/2014/ Met Office Surface Exchange Scheme (MOSES), Essery et al. 2001 www. metoffice. gov. uk/media/pdf/9/j/HCTN_30. pdf SNTHERM, Jordan 1991 https: //webcam. crrel. usace. army. mil/SNTHERM/ SNOWPACK, Lehning et al. 2002 http: //www. sciencedirect. com/science/article/pii/S 0165232 X 02000733 Also empirical relationships between SSA and snow type and density Domine et al. (2007). J. Geophys. Res. , doi: 10. 1029/2006 JF 000512

Microstructure in snow models Thermal Hydraulic Mechanical Optical Density Liquid water d. T/dz Snowpack Temperature SNTHERM Bond size MOSES Optical radius Crocus Shape CLM Grain size Model Properties Predictors Descriptors

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

Snow model layering

No. SREx IOA @ 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 Eulerian layers, simulated snow temperatures MOSES r = 0. 06 CLM r = 0. 41 SNTHERM r = 0. 66 MOSES r = 0. 32 CLM r = 0. 53 SNTHERM r = 0. 59

Grain size and SSA simulations Lagrangian layers, measured snow temperatures 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

Tentative conclusions and future directions