1/16 S ystem for P rediction of E nvironmental E mergency D ose I nformation M ulti-model P ackage Incorporation of Tritium Transport Processes into Incorporation of Tritium Transport Processes into Atmosphere- -soil soil- -vegetation Model: SOLVEG vegetation Model: SOLVEG Atmosphere ~HTO transport from atmosphere to bare soil~ ~HTO transport from atmosphere to bare soil~ Haruyasu Nagai Research Group for Environmental Science, Japan Atomic Energy Agency
Land surface model SOLVEG2 2/16 Outline of Study Objectives � Development of sophisticated land surface model including radionuclide (Tritium) transport processes � Understand and predict behavior of radionuclide at land-surface by numerical experiment Model development � Step 1: Heat and water exchange processes � Step 2: Canopy radiation and stomatal resistance � SOLVEG � SOLVEG2 � Step 3: CO 2 exchange processes � EMRAS-II: Radionuclide transport processes (THO)
Land surface model SOLVEG2 3/16 Description of model Overview Overview One-dimensional multi-layer sub-models for atmosphere, soil, and vegetation. Structure Scheme for radiation transmission in the canopy and CO 2 exchange processes. Simulation of water, heat, and CO 2 exchanges Function in the atmosphere-soil-vegetation system. Diurnal variation and seasonal change. Objectives Atmospheric surface layer, root zone soil, and vegetation canopy. Variables Variables Horizontal wind components (u, v) Potential temperature Atmosphere Specific humidity Fog water CO 2 concentration Turbulence kinetic energy, length scale Temperature Volumetric water content Soil Specific humidity of soil air CO 2 concentration Leaf surface temperature Leaf surface liquid water Vegetation Vertical liquid water flux in canopy Leaf CO 2 concentration Down/upward solar radiation (direct and diffuse, visible and near-infrared) Radiation Down/upward long-wave radiation
Land surface model SOLVEG2 4/16 Physical processes Physical processes are calculated at each layer of vertical multi-layer model Bold: main var., Underlined: processes, Red: heat/rad., Blue: water, Green: CO 2 Atmosphere Diffusion Wind, Turbulence Rain Short wave Temperature Long wave CO 2 concentration Latent heat Fog water Water vapor Phase change Heat exchange, Vegetation Absorption, Emission Scattering Evaporation/condensation Interception Photosynthesis Heat/water budget CO 2 assimilation , Temperature, water Drip Transpiration Surface exchange: Momentum, Heat, Water, CO 2 Surface water Soil Surface budget: Heat, Water, CO 2 CO 2 conc. Temperature Root/soil respiration Latent heat Liquid water Water vapor Advection Uptake: Water & CO 2 Phase change & Diffusion
Land surface model SOLVEG2 5/16 Basic equations (1): heat, water, momentum ∂φ ∂ ∂φ φ = θ λ Atmosphere = + , , , , , , Diffusion: u v q e e w K F φ a f ∂ ∂ ∂ z t z z Source term Boundary condition Evaporation/ ∂ ∂ ∂ ∂ T T H C E T = + − Soil Heat: s s b w w s K condensation ∂ ∂ ∂ ρ ρ ∂ T t z z C C z s s s s ∂ η ⎛ ∂ ⎞ 1 E ⎜ ⎟ = − = − + + Liquid water: w w E E H lE ⎜ ⎟ ∂ ρ ∂ b b t b ⎝ ⎠ t z w [ ] ∂ η − η ∂ ∂ ( ) Water vapor: q q E = η + ws w s s b ( ) D f ∂ ∂ ∂ ρ w a w t z z Transpiration Vegetation Heat budget: = + + = + R H lE H E E E c c c p c d s dw = − + − Leaf water: d E E E P int d cap d dt Water flux: dP ( ) = − + − r a E P E E int d pr col dz Net radiation Radiation Short wave: Downward and upward transfer (Next slide) Direct (visible + near-infrared) + Diffuse (visible + near-infrared) Long wave: Downward and upward transfer
Land surface model SOLVEG2 6/16 Basic equations (2): radiation Radiation scheme (coefficients based on Verstraete 1987, 1988) ↓ dS ( ) Short: (direct) = + ′ + ′ ↓ Scattering d , aF a A S rd w w d dz Leaf projection cf.: F rd ↓ [ ] ( ) (diffuse) dS ( ) Scattering cf.: = − + ′ + ′ ↓ − + ′ ↑ − ↓ s 1 , aF f a A S aF f A S aF f S rs sf w w s rs sb w s rd df d dz f df (forward), (visible) ↑ [ ] ( ) ( ) dS ′ ′ ′ = − − + + ↑ + + ↓ + ↓ s 1 . aF f a A S aF f A S aF f S f db (backward) rs sf w w s rs sb w s rd db d dz (near-IR) Depend on solar angle and leaf surface angle [ ] ( ) , ↓ ( ) dL = − ↓ − ↑ − ε σ + ↓ − σ Long wave: 4 4 1 aF f L f L T k w L T rs sf sb c c l l a dz [ ] ( ) . ↑ ( ) dL = − − ↑ − ↓ − ε σ − ↑ − σ 4 4 1 aF f L f L T k w L T rs sf sb c c l l a dz Leaf projection cf.: F rs Forward scattering cf.: f sf Back scattering cf.: f sb └ Depend on leaf surface angle ┘ Depend on leaf area density
Land surface model SOLVEG2 7/16 Basic equations (3): CO 2 , stomata resistance CO 2 assimilation ( A n ): Farquhar et al. (1980) ( ) = − min , , A w w w R n c e s d : Depend on PAR, leaf CO 2 conc., temperature w c , w e , w s , R d Stomatal resistance ( r s ): Collatz et al. (1991, 1992) 1 A e = = + n s g m p b ( ) CO 2 CO s a r c e T 2 s s sat v m (constant), b (minimum conductance) ⇒ measured parameter CO 2 partial pressure at leaf surface c s e s / e sat ( T v ) Relative humidity at leaf surface Atmospheric pressure p a 2 options Stomatal resistance (Jarvis scheme): BATS (Dickinson et al. 1993) = − − − 1 1 1 r s,min ⇒ measured parameter r r f f f f No CO 2 No CO , min s s r s m t 2 f r , f s , f m , f t : Functions of PAR, soil water, humidity, temperature
Land surface model SOLVEG2 8/16 Basic equations (4): soil CO 2 Soil CO 2 conservation: Simunek and Suarez (1993) ∂ ∂ ∂ ∂ c = − − + * * a V c D E c E K RTc S ∂ ∂ ∂ ∂ E a E E a t H a t z z z ( ) = η − η + η Volume: , V K RT E ws w H w ( ) = η − η + η Diffusion: , D D K RT D E ws w a H w w = + * * * Advection: , E E K RTE E a H w ⇒ Treatment of CO 2 in gas and aqueous phase together by Henry’s Law: c w = K H RTc a CO 2 conc. in soil air c a η w Volumetric water content * Root uptake (transpiration) E t CO 2 source term ( ＝ soil: S s ＋ root: S r ) S ( ) ( ) ( ) ( ) ( ) = η S S f z f f T f c f t 0 s s s s w s s a s ( ) ( ) ( ) ( ) ( ) = η S S f z f f T f c f t 0 r r r r w r r a r
Land surface model SOLVEG2 9/16 Water and CO 2 fluxes at grassland � Good performance for water and CO 2 exchanges at grassland (AmeriFlux data) Diurnal variation and seasonal change are well reproduced. � It can be applied for detailed simulation of 3 H and 14 C transport. Latent heat (water vapor) flux 6 0 0 Observation -2 ) 4 0 0 ○ : daily mean m W 2 0 0 ◇ : daily max ( LH ＋ : daily min 0 - 2 0 0 9 7 1 2 7 1 5 7 1 8 7 2 1 7 2 4 7 2 7 7 3 0 7 Calculation CO 2 flux ― : daily mean J u l i a n d a y s (L S T ) ― : daily max 2 0 -1 ) ― : daily min s -2 0 m μm ol Upward positive - 2 0 ( FC - 4 0 9 7 1 2 7 1 5 7 1 8 7 2 1 7 2 4 7 2 7 7 3 0 7 APR MAY JUN JUL AUG SEP OCT NOV J u l i a n d a y s (L S T )
Land surface model SOLVEG2 10/16 Incorporation of HTO transport processes Concept � Process based HTO transport model to simulate dynamic behavior of HTO in air-soil-plant system � Explicit calculation of HTO transport in a similar way as water and vapor transport Model development � Step 1: transport in the atmosphere and bare soil (no decay) • In-soil transport by Yamazawa (2001) applied for BIOMASS Theme 3-F (rise of HTO from contaminated groundwater) • Atmospheric transport for HTO vapor (1-D diffusion eq.) • Test calculation using met. data of AmeriFlux (previous slide) � Step 2: inclusion of plant uptake processes � Step 3: OBT production and translocation
Land surface model SOLVEG2 11/16 Incorporation of HTO transport processes Water and vapor exchange processes Water and vapor exchange processes external input: precipitation HTO transport process accretion Fog water Leaf surface water Calculate HTO conc. for Water budget eq. Diffusion equation interception each variable of water stomata condensation evaporation/ accretion transpi- evaporation condensation ration drip Water vapor in air Precipitation New variable: Conservation equation Diffusion equation Plant water of vertical flux evaporation/ condensation Water budget eq. Step 2 drip (root uptake - transpiration) evaporation/ condensation Ground surface water budget eq. run-off Step 3 Liquid water in soil Water vapor in soil OBT formation and evaporation/ Transport equation Step 1 Diffusion eq. condensation translocation uptake by root
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