ISBA. the model for natural continental surfaces

Transcription

1 ISBA the model for natural continental surfaces

2 ISBA Model of the «nature» part of SURFEX Exchanges of energy, water, carbon, (dust, snow with the atmosphere and the hydrology Work with the «mean» properties of the mesh (aggregation rules, or on a number of patches (1 to 12, according to the user's choice. In the case of patches, each models are independent (no lateral transfers. The parameters and the surface description. Force restore model : energy and water Multilayer model «diffusion» Snow Phosynthesis and carbon cycle

3 Introduction : main parameters Primary parameters Soil Clay fraction (X clay Sand fraction (Y sand Vegetation Type of cover Both Soil depth (d i i =1,2,... Albedo (α Emissivity(β Secondary parameters Saturation (or porosity (W sat Field capacity (W fc Wilting point (W wilt Minimal surface resistance (R smin Leaf area index (LAI Roughness lenght for momentum and heat z 0 and z 0h Fraction of vegetation (veg

4 Description of the surface : fraction of vegetation and snow per patch 4 Vegetation soil Veg 1-Veg

5 Description of the surface : fraction of vegetation and snow per patch 5 Vegetation soil snow 1-p snv p snv p sng 1-p sng Veg 1-Veg Snow fraction : p sn = p snv + p sng Albedo : α total = (1-p snv α veg + p sn α snow + (1-p sng α soil Emissivity : ε total = (1-p snv ε veg + p sn ε snow + (1-p sng ε soil

6 ISBA : soil description Option Namelist : CISBA Temperature profile Hydrology profile 2-L 3L Ts : surface temperature T2 : deep temperature Surface layer (1cm Root zone Surface layer (1cm Root zone Sub-root zone DIF N soil layers (default = 14 layers LTEMP_ARP=.T. N temperature in NAM_SOILTEMP_ARP root zone : depends Force restore on vegetation extended to 4 layers for temperature (Richard's (climate equations runs

7 ISBA : the basic version : CISBA=2-L 5 prognostic variables (except snow : Ts, T 2, Wr, Wg, W 2

8 Surface energy budget : temperature T s dt =C T (R n H LE 2π τ ( T s T 2 T 2 dt = 1 τ ( T s T 2 Inertia coefficent : C T = 1 /[ veg (1 p snv C v + p sn C n + (1 veg (1 p sng C g ]

9 Surface hydrologic budget : interception reservoir E c W rmax W r δ = fraction of vegetation covered by water δ= (W r / W r max 2/3 Deardorff, 1978.

10 Surface hydrologic budget : interception reservoir E c W r t = (1 p nv vegp E c R r W rmax W r R r δ = fraction of vegetation covered by water δ= (W r / W r max 2/3 R r =max( 0, W r W r max Δt W r max = 0. 2 veglai Deardorff, 1978.

11 Hydrological budget : evapotranspiration (in the absence of snow E=E g +E veg E veg =E c +E ETR E veg =veg (1 p nv ρ a C H V a h v [q sat (T s q a ] Snow free vegetation fraction Surface Atmosphere exchange

12 Hydrological budget : evapotranspiration (in the absence of snow E=E g +E veg E veg =E c +E ETR Halstead coef E veg =veg (1 p nv ρ a C H V a h v [q sat (T s q a ] Snow free vegetation fraction Surface Atmosphere exchange h v =δ+ (1 δ R a /( R a +R s with R a = 1 Potential E c R a x E tr C h V a

13 Hydrological budget : evapotranspiration (in the absence of snow E=E g +E veg E veg =E c +E ETR Haltead coef Surface resistance E veg =veg (1 p nv ρ a C H V a h v [q sat (T s q a ] Snow free vegetation fraction Surface Atmosphere exchange h v =δ+ (1 δ R a /( R a +R s with R a = 1 Potential E c R a x E tr C h V a

14 Hydrology : transfers in the soil (FR w 1 t w 2 t = C 1 ρ w d 1 [ I r E g ] D 1 = 1 ρ w d 2 (I r E g E tr K 2 w min w 1 w sat w min w 2 w sat w2 : total water content, w1 : fraction of tw2 near thhe surface Infiltration : I r =(1 veg P+R r +S m Q s Surface runoff : Q s = d 2 ρ w Δt max (0, w 2 w sat

15 Water Budget : Soil moisture 1 5 NAM_ISBA CISBA= 2-L Surface runoff (Q s Plant transpiration (E tr Infiltration I r Bare soil evaporation (E soil Total soil depth = Rooting depth (d 2 w 1 w 2 Diffusion D 1 Drainage K 2

16 Water Budget : Soil moisture 1 6 Surface runoff (Q s Rooting depth (d 2 Total soil depth (d 3 Plant transpiration (E tr w 1 w 2 w 3 Infiltration NAM_ISBA Bare soil evaporation (E soil Diffusion D 1 Diffusion D 2 & drainage K 2 CISBA= 3-L Drainage K 3

17 Specific options: Sub-Grid Drainage 1 7 Allow a deep drainage under the field capacity (Etchevers et al Especially relevant to simulate low summer discharges. K 2 = C 3 K 3 = max τd 2 [ ω d2, (w 2 w fc ] C 3 τ (d 3 d 2 max [ω d3, (w 3 w fc ] w drain uniform value (local or over a domain ω d i =w drain min (w i,w fc w min w fc w min w min =0.001 or w wilt with CKSAT= SGH Gravitational drainage NAM_ISBA XUNIF_WDRAIN= K i Linear sub-grid drainage w drain non uniform values over a domain NAM_ISBA YWDRAIN= Input file name YWDRAINFILETYPE= input file format 0 w wilt w fc w i

18 Specific options: Exponential profile of k sat 1 8 The soil column assumes an exponential profile of k sat with soil depth. The main hypothesis is that roots and organics matter favor the development of macrospores and enhance the water movement near the surface while the soil compaction is an obstacle for deep soil percolation (Decharme et al Compacted value used by default ISBA k sat,c k sat k sat ( z =k sat,c e f (z d c d c = d 2 : compacted depth f <= 2m -1 : decay factor d 2 d 3 Depth z Homogeneous initial profile All force restore coefficient (C 1, C 2, C 3, C 4 as well as w geq have been analytically recalculated. NAM_ISBA_SGH CKSAT= SGH

19 Hydrologic specific options 1 9 Spatial variability of hydrologic V processes : Precipitation Topography Soil properties Vegetation (Tiles Exponential profile of k sat with soil depth NAM_ISBA Especially relevant NPATCH=12 for large (global and/or NAM_ISBA_SGH regional applications CRAIN = SGH CHORT= SGH CRUNOFF= DT92 or SGH CKSAT= SGH ISBA grid cell Vegetation (Tiles Others

20 Model «Diffusion» N layers CISBA=DIF Explicit soil DIFfusion Option: Downgradient thermal transfer and Richard's Eq. 3 Prognostic equations: N-layers for temperature, liquid water and soil ice: Total soil water

21 Default configuration for ISBA-DF (14L Bare soil Crops Equatorial forests Infiltration T sol T sol T sol Infiltration Infiltration Dense roots Dense roots (m Source : B. Decharme, CNRM

22 ISBA-DIF : main options Icing in the soil : CSOILFRZ=DEF : The freeze/thaw rates are proportional to the temperature depression and the available liquid/ice. CSOILFRZ=LWT : As opposed to potentially freezing ALL liquid water, this method uses the freezing curve method. The maximum liquid water content for a given texture is a function of T... More physical... also avoids numerical problems since liquid water content stays above minimum numerical threshold Hydrology : NAM_ISBA XUNIF_WDRAIN= xxx : subgrid drainage (WDRAIN CKSAT= SGH : exponential profile of hydraulic conductivity

23 The snow models of ISBA EBA D95 (default 1 reservoir, 2 prognostic variables (Wn, albédo model : ARPEGE/PN, ALADIN/PN (Bazile 1 reservoir, 3 prognostic variables (Wn, albedo, density (climate model, AROME, offline (Douville, L ISBA-ES (explicit snow multi-layer, 4 prognostic variables offline (chaîne SIM, and climate applications CRO CROCUS/SURFEX : multilayer model based on ISBA- ES and the the snow model CROCUS ( description of snow grains, incresed number of layers (Brun et al., Vionnet et al.

24 Zoom on ISBA-ES (1/2 - N layer- snow scheme (default : 3 - snow setlement (including settlement due to melting - Radiative tranfers - explicit surface energy budget : albedo, density, SWE and H (enthalpy - liquid water content H : 2 variables in one!

25 Zoom on ISBA-ES (2/2 The snow has a separate energy budget Snow layers management CSNOWRES=RIL to maintain turbulent exchanges under very stable conditions Develoment of a separate energy budget for snow/vegatation

26 Carbon options (ISBA-A-gs, ISBA-CC Carbon fluxes: Photosynthesis, ecosystem respiration, net exchanges with the ecosystem Biomass (including LAI : leaf area index Evolution of the above-ground and below-groude biomass Carbon stock Organic matters, mulch, wood Better representation of plant behaviours (C3 vs C4, LAI consistent with water and carbon fluxes, assimilation of vegetation data NPATCH = 12 mandatory

27 ISBA standard vs A-gs Met. forcing LAI ISBA-Standard LE, H, Rn, W, Ts Met. forcing LAI Active Biomass ISBA-A-g s LE, H, Rn, W, Ts CO 2 Flux [CO 2 ] atm (Calvet et al, 1998

28 ISBA : option CPHOTO NON AGS* LAI* AST LST* NIT ISBA-standard (default NON + explicit photosynthesis AGS+LAI evolution AGS+ improved hydric stress LAI+improved hydric stress LST+nitrogen dilution * : not recommended (obsolete

29 The ISBA -MEB (multi-energy balance Now no interaction between high vegetation and snow or bare soil/lower vegetation Objectives : introduction of a diagnostic canopy air temperature that interacts with high/low vegetation To be introduced in the next version (V8

30 ISBA : options and namelists NAM_ISBA NPATCH, CISBA, CPHOTO, NGROUND_LAYER,SAND,CLAY,WDRAIN,CTI NAM_DATA_ISBA NAM_PREP_ISBA NAM_PREP_ISBA_SNOW NAM_PREP_ISBA_CARBON NAM_ISBAn NAM_SGH_ISBAn NAM_DIAG_ISBA NAM_SOIL_TEMP_ARP Init PGD ISBA ( ECOCLIMAP=.F. : NTIME, VEGTYPE, VEG,LAI, Z0, EMIS, DG,ROOTFRAC,RSMIN, Initial field for ISBA + date CSNOW, initial field for SNOW, +date RESPL XTSEP, Options of calculation for some parameters (conduction, Z0 Options subgrid hydrology (KSAT, WDRAIN, Diagnostics for ISBA LTEMP_ARP (4 temperatures FR climat See the user's guide for output variables