1. Snow processes in ORCHIDEE Tao Wang, C. Ottlé, P. Ciais, etc..

2. Thicker snow, warmer soil temp. Prolonged snow, later vegetation greening earlier snowmelt, earlier spring runoff Less snow, warmer air temperatures Snow roles in high latitudes: NDVI (30 May - 5 June)

3. EnEn P HLE K in L in T, D, ρ T surf J W s, D, ρ Skin layer T surf > 0, snow melt occurs; Heat Water Old ORCHIDEE (ORC-O, 1-layer) Top soil layer composite ORCHIDEE Snow developments Single layer vs. Three layers Composite vs. Separate snow structure Snow density and snow thermal conductivity (constant vs. variable) Freezing and refreezing processes (no vs. yes) Water flow between layers (no vs. yes) 3 EnEn H LE K in L in K1K1 K2K2 K3K3 Q 1, T 1, D 1, ρ 1 Q 2, T 2, D 2, ρ 2 Q 3, T 3, D 3, ρ 3 J1J1 J2J2 J3J3 QpQp HeatWater P P1P1 P2P2 P3P3 W s1, W l1, D 1, ρ 1 W s2, W l2, D 2, ρ 2 W s3, W l3, D 3, ρ 3 Top soil layer Separate New ORCHIDEE (ORC-ES, 3-layers)

4. Sensitivity tests (Morris method) Albedo-related Thermal conductivity- related Snow compaction factors ORCHIDEE-ES on Col de Porte Most important Very important for soil temperature simulation Very important for snow depth simulation

5. Evaluation results (CDP-snow depth)

6. Evaluation results (Albedo and soil temperature), Col de Porte, mean seasonal cycle (1993-2011)

7. How to constrain snow albedo feedback in model ? Option 1: Developing physical-based snow albedo scheme taking into account snow grain size, impurity content etc Albedo = f(snow grain size, impurity, sun angle, snow depth) Albedo = f(snow age)

8. How to constrain snow albedo feedback in model ? Option 1: Developing physical-based snow albedo scheme taking into account snow grain size, impurity content etc Option 2: Data assimilation from in-situ or albedo product (GlobAlbedo) In-situ snow albedo assimilation into ORCHIDEE-ES (alpine site, WFJ)

9. How to constrain snow albedo feedback in model ? Wang et al. (in preparation) Control Assimil. April Reflected radiation (albedo x SWdown) Option 1: Developing physical-based snow albedo scheme taking into account snow grain size, impurity content etc Option 2: Data assimilation from in-situ or albedo product (GlobAlbedo)