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Improvement and Evaluation of Multilayer Explicit Soil and Snow Schemes in SURFEX

This article discusses the improvement and evaluation of multilayer explicit soil and snow schemes in the SURFEX model. It includes a review of the ISBA scheme and validation in France and Siberia, as well as the adaptation of the scheme for boreal regions. The article also explores the incorporation of soil organic carbon content and the explicit snow scheme improvements.

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Improvement and Evaluation of Multilayer Explicit Soil and Snow Schemes in SURFEX

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  1. Amélioration/Évaluation des schémas explicites multicouches de sol et de neige dans SURFEX Bertrand Decharme, Eric Brun, Patrick LeMoigne, Aaron Boone, Christine Delire , Stéphanie Faroux, Eric Martin, Joël Noilhan • Revue d’ISBA et validation sur la France • Validation des schémas de sol et de neige la Sibérie • Conclusions et Perspectives

  2. Soil moisture Soil ice Soil/Root depth drainage ISBA-DF Land Surface Scheme ISBA-DF: land surface water and energy budgets using diffusive equations (Boone et al. 2000; Decharme et al. 2011) Soil hydrology uses the “mixed” form of the Richards equation: Humidity Vapor The soil heat transfer uses the one-dimensional Fourier law:

  3. ISBA-DF Soil Parameters Soil-water retention and conductivity functions from Brooks and Corey [1966] : Hydrodynamic parameters (wsat, ψsat, ksat) from soil mineral textures using Clapp and Hornberger [1978] and Noilhan and Lacarrère [1995] pedotransfer functions Soil heat capacity from Farouki [1986] : Total soil heat capacity is computed as the sum of the water and ice heat capacity and the heat capacity of the soil mineralmatrix (csol = 1979 kJ.K-1.m-3) Soil conductivity from Peters-Lidard et al. [1998] : Soil mineral thermal conductivity is expressed as a function of volumetric water and ice content, soil porosity, soil quartz content and dry soil conductivity following the method of Johansen [1975] with modifications by Farouki [1986] with fu,i = unfrozen soil fraction

  4. ISBA-DF Soil Configuration Root depth from Canadel et al. [1996] Root profile from Jackson et al. [1996] Hydro depth Thermal depth (Decharme et al. 2013, JGR)

  5. Experimental design to validate ISBA-DF over France Forcing SAFRAN 1-hr, 8km, 1992-2012 20 years Spin up (4 x 1992-1996) Vegetation & Soil parameters ECOCLIMAP & HWSD(1km) PFTs, LAI, Clay, Sand, etc… SURFEX ISBA Discharges and Soil Temperature stations Soil temperature Runoff & Drainage MODCOU Discharges (Decharme et al. 2013, JGR)

  6. Soil Temperature: monthly climatology over 1992 – 2012 (Decharme et al. 2013, JGR)

  7. Discharges: daily climatology over 1992 – 2012 (Decharme et al. 2013, JGR)

  8. Discharges global statistics over 1992 – 2012 (Decharme et al. 2013, JGR)

  9. Discharges global statistics over 1992 – 2012 • DF well reproduces soil temepratures and river discharges • Soil must be sufficiently deep to compute a realistic soil temperature profile, while in terms of hydrology, if lateral soil-river exchanges are not parameterized, the soil column should be substantially thinner in order to simulate realistic river discharges and therefore surface fluxes. (Decharme et al. 2013, JGR)

  10. ISBA-DF scheme adaptation for Boreal regions Problem: ISBA only accounts for mineral soil hydro and thermal properties while Organic Carbon is largely present over high latitude regions Soil Organic Carbon (SOC) content (kg.m-2) builds using HWSD database at 1km http://webarchive.iiasa.ac.at/Research/LUC/External-World-soil-database/HTML/

  11. Discretization of Soil Peat Properties with depth Letts et al. (1999)

  12. Soil peat properties profiles with depth Letts et al. (1999) ISBA zsurf = 0.01 m zbottom = 1 m

  13. Correction of Mineral Soil Properties using Peat Properties Fraction of organic carbon in the soil (Lawrence et Slater 2008) SOCtop = 10 kg/m2 SOCsub = 12 kg/m2

  14. Correction of Mineral Soil Properties using Peat Properties Fraction of organic carbon in the soil (Lawrence et Slater 2008) Mineral, Peat, and Combined Soil Properties SOCtop = 10 kg/m2 SOCsub = 12 kg/m2

  15. ISBA Explicit Snow (ES) improvements

  16. Snowpack Temperature validation at DOMEC (Antarctica) For all scheme, 19 layers are used with the same initialization

  17. Experimental design to validate ISBA Explicit Snow and Soil over “open field” Siberian data Forcing EAR-I. Reanalysis + GPCC 3-hr, 0.5°, 1979-1993 100 years Spin up (10 x 1979-1988) Soil parameters HWSD(1km) Clay, Sand, Topsoil and Subsoil OC SURFEX (ISBA) Snow depth Soil temperature

  18. Snow Depth: DJF bias over 1979 – 1993 Bias 0.004 m Bias -0.014 m Bias -0.004 m

  19. Snow Depth: daily climatology over 1979 – 1993

  20. Soil Temperature at -20cm: global statistics over 1979 – 1993 -1.17 °C bias -0.10 °C -0.40 °C 2.45 °C rms of anomalies 2.22 °C 2.02 °C

  21. Soil Temperature: monthly climatology over 1979 – 1993

  22. Soil Temperature: monthly climatology over 1979 – 1993

  23. Simulation of Permafrost at Global Scale • 0.5°x0.5° simulation using ERA-I forçing 1979-2012 • Permafrost types given by NSIDC (Brown et al. 2001)

  24. Conclusions & Perspectives • New scheme allows a good representation of river discharges, soil temperatures and snow depth. • Must be confirmed with new Multi-Energy-Balance scheme (Adrien Napoly) and using more snow data (Forest sites) • Evaluation on-line in CNRM-CM (Jeanne Colin) • Coupling with aquifer scheme (Vergnes et al. 2014; I-GEM project) • Coupling with carbon cycle and methane emission processes (Xavier Morel thesis; APT project)

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