New options for snow drift and blowing snow module SYTRON

The snowdrift scheme increases compaction and metamorphism due to snowdrift (Brun et al, 1997 ; Vionnet et al, 2012) but it does not transfer mass between grid points.
To activate the scheme, the LSNOWDRIFT logical key is replaced by CSNOWDRIFT option with 4 possible values:
CSNOWDRIFT='NONE' snowdrift scheme disactivated
CSNOWDRIFT='DFLT' (default) snowdrift scheme activated, properties of falling snow are purely dendritic
CSNOWDRIFT='VI13' snowdrift scheme activated, properties of falling snow are taken from Vionnet et al (2013)
CSNOWDRIFT='GA01' snowdrift scheme activated, properties of falling snow are taken from Gallée et al (2001)

The modification of initial microstructure in options VI13 and GA01 affects in particular the threshold wind speed for snow transport when blowing occurs with concurrent snowfall.

LSNOWSYTRON logical (default FALSE) key allows to activate the blowing snow module SYTRON (Vionnet et al, 2018) which simulates erosion and accumulation between opposite slope aspects in the topographic-based geometry used by MF operational simulations for avalanche hazard forecasting. This option must be maintained to FALSE in all other simulation geometries. It is recommended to combine LSNOWSYTRON=T with CSNOWDRIFT=VI13 (better skill scores in terms of blowing snow occurrence)

Gallée, H., Guyomarc'h, G., & Brun, E. (2001). Impact of snow drift on the Antarctic ice sheet surface mass balance: possible sensitivity to snow-surface properties. Boundary-Layer Meteorology, 99(1), 1-19.
Vionnet, V., Guyomarc’h, G., Bouvet, F. N., Martin, E., Durand, Y., Bellot, H., ... & Puglièse, P. (2013). Occurrence of blowing snow events at an alpine site over a 10-year period: observations and modelling. Advances in Water Resources, 55, 53-63.
Vionnet, V., Guyomarc’h G., Lafaysse, M., Naaim-Bouvet, F., Giraud, G. and Deliot, Y. : Operational implementation and evaluation of a blowing snow scheme for avalanche hazard forecasting, Cold Reg. Sci. Technol. 147, 1-10, Doi : 10.1016/j.coldregions.2017.12.006, 2018.
Brun, E., Martin, E., & Spiridonov, V. (1997). Coupling a multi-layered snow model with a GCM. Annals of Glaciology, 25, 66-72.
Vionnet, V., Brun, E., Morin, S., Boone, A., Faroux, S., Le Moigne, P., Martin, E., and Willemet, J.-M. : The detailed snowpack scheme Crocus and its implementation in SURFEX v7.2, Geosci. Model Dev., 5, 773-791, doi :10.5194/gmd-5-773-2012, 2012.

Developer name

Vincent Vionnet

Date of start of development

Commit number before the development

Current status

Stable in branches cen and SURFEX_V9_dev

Evaluated against SURFEX test database ?


New test added in the database (if yes, describe)


Changes in namelist



CSNOWDRIFT replaces LSNOWDRIFT logical key in previous options

Other required changes (forcing files, snowtools code or options, VORTEX, ....)

The diagnostic of blowing snow mass from the SYTRON module can be obtained by adding the field SYTFLX_ISBA in the CSELECT list of variables in NAM_SURF_SNOW_CSTS.