1. Snow analysis, parameterisation of deposition and melting Ekaterina Machulskaya Hydrometeorological Centre of Russian Federation, Moscow, Russia Moscow State University, Russia

2. Motivation Snow model description Results discussion Conclusions and outlook Outline

3. Motivation

4. Snow models description Heat conduction Melting when snow surface temperature > 0°C or when soil surface temperature > 0°C Heat conduction Liquid water transport Gravitational compaction + metamorphosis Solar radiation penetration 1 layer Arbitrary number of layers; heat conduction: implicit (combined with soil heat conduction), latent heat and solar radiation: source terms Numerical schemes Implemented processes TERRA ctrl TERRA + new snow

5. Implemented processes (2) - snow temperature,- snow liquid water content, - snow density,- snow specific heat content, - snow heat conductivity, - latent heat for freezing/melting, - melting rate,- refreezing rate,- infiltration rate due to gravity Water percolation: - snow hydravlic conductivity,- snow water holding capacity, - snow porosity Heat and water transport

6. Gravitational compaction and metamorphosis describes the gravity effect Where term describes the snow metamorphosis, = 75 Pa - the snow compaction viscosity Solar radiation penetration Implemented processes (3)

7. Results discussion: snow water-equivalent depth, Valdai, 1966-1972

8. Results discussion: snow mask, spring 2008 15.03.2008 ctrl new

9. Results discussion: snow water-equivalent depth, spring 2008 new – ctrl 15.03.2008 25.03.2008

10. Summary A new, more physically based parameterization of snow is suggested and implemented into TERRA-standalone. As the main component, this scheme includes description of the water phase transitions within snowpack. By means of the Valdai long-term data an comparison with the current snow model incorporated in COSMO is done. The new scheme represents the snow evolution more realistically, particularly during melting period. Ongoing work Evaluation of the results obtained for the COSMO-EU domain during off-line experiments

11. Outlook Verification of the new model in operational mode Code consolidation + scientific and technical documentation Winter 2008/09: verification of the new scheme for the COSMO-RU domain

12. Thank you for your attention!