1/18 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 Atmosphere-soil-vegetation Model: SOLVEG ~OBT dynamics in plants using the SOLVEG code after an accidental tritium release~ Haruyasu Nagai, Masakazu Ota Research Group for Environmental Science, Japan Atomic Energy Agency
Land surface model SOLVEG2 2/18 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, OBT)
Land surface model SOLVEG2 3/18 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 Wind, Turbulence Diffusion 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 4/18 Basic equations (1): heat, water, momentum ∂φ ∂ ∂φ Atmosphere φ = θ λ Diffusion: u , v , , q , e , e , w = + K F a f φ ∂ ∂ z ∂ t z z Source term Boundary condition Evaporation/ ∂ ∂ ∂ ∂ T T H C E T Soil Heat: = + − s K s b w w s condensation T ∂ ∂ ∂ ρ ρ ∂ t z z C C z s s s s ⎛ ⎞ ∂ η ∂ E 1 Liquid water: ⎜ ⎟ = − = − + + w w H lE E E ⎜ ⎟ b b ∂ ρ ∂ t b t z ⎝ ⎠ w [ ] ∂ η − η ∂ ∂ Water vapor: ( ) q q E = η + ws w s D f ( ) s b w a w ∂ ∂ ∂ ρ 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 5/18 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 aF 1 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 aF 1 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 Long wave: ↓ ↑ ↓ = − − − ε σ 4 + − σ 4 aF 1 f L f L T k w L T rs sf sb c c l l a dz [ ] ( ) . ↑ ( ) dL = − − ↑ − ↓ − ε σ − ↑ − σ 4 4 aF 1 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 area density └ Depend on leaf surface angle ┘
Land surface model SOLVEG2 6/18 Basic equations (3): CO 2 , stomata resistance CO 2 assimilation ( A n ): Farquhar et al. (1980) ( ) = − A min w , w , w R n c e s d w c , w e , w s , R d : Depend on PAR, leaf CO 2 conc., temperature Stomatal resistance ( r s ): Collatz et al. (1991, 1992) 1 A e = = + g m n s p b ( ) s a r c e T s s sat v m (constant), b (minimum conductance) ⇒ measured parameter c s CO 2 partial pressure at leaf surface e s / e sat ( T v ) Relative humidity at leaf surface p a Atmospheric pressure 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 s s , min r s m t f r , f s , f m , f t : Functions of PAR, soil water, humidity, temperature
Land surface model SOLVEG2 7/18 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 c a CO 2 conc. in soil air η w Volumetric water content E t * Root uptake (transpiration) S CO 2 source term ( ＝ soil: S s ＋ root: S r ) ( ) ( ) ( ) ( ) ( ) = η S S f z f f T f c f t s s 0 s s w s s a s ( ) ( ) ( ) ( ) ( ) = η S S f z f f T f c f t r r 0 r r w r r a r
Land surface model SOLVEG2 8/18 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 4 0 0 -2 ) ○ : daily mean LH (W m 2 0 0 ◇ : daily max ＋ : daily min 0 - 2 0 0 Calculation 9 7 1 2 7 1 5 7 1 8 7 2 1 7 2 4 7 2 7 7 3 0 7 CO 2 flux ― : daily mean J u lia n d a y s (L S T ) ― : daily max 2 0 -1 ) ― : daily min -2 s 0 FC (μmol m Upward positive - 2 0 - 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 lia n d a y s (L S T )
Land surface model SOLVEG2 9/18 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 formation and translocation
Land surface model SOLVEG2 10/18 Incorporation of HTO transport 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 each variable of water interception stomata condensation evaporation/ accretion transpi- evaporation condensation ration drip Water vapor in air Precipitation New variable: Conservation equation Diffusion equation Plant water evaporation/ of vertical flux 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/ Step 1 Diffusion eq. Transport equation condensation translocation uptake by root
Land surface model SOLVEG2 11/18 In-soil HTO transport processes Soil HTO transport: Yamazawa (2001) applied for BIOMASS theme 3 ∂ ∂ ∂ ∂ χ ⎛ ⎞ 1 η χ = − χ + − ⎜ ⎟ E D w e w w w w Tw b Liquid phase: ∂ ρ ∂ ∂ ∂ t z z ⎝ z ⎠ w +: evaporation ∂ ∂ ∂ χ ⎡ ⎤ [ ] ( ) ( ) -: Condensation η − η χ = η + sa D f e Gas phase: ⎢ ⎥ ws w sa Ta sa w b ∂ ∂ ∂ t z z ⎣ ⎦ ∂ χ ( ) ( ) − η + = χ − χ Surface B.C.: D f sa e c u Atmosphere- Ta sa w 0 b 0 E 0 r sa 0 r ∂ z = land exchange z 0 χ w , χ sa , χ r HTO conc. in soil water (Bq/m 3 -water), soil air and air (Bq/m 3 -air) η w , η sw Volumetric soil water content and saturated value (m 3 /m 3 ) ρ w Density of soil water (kg/m 3 ) E w Vertical liquid water flux (kg/m 2 /s) D Tw , D ta Effective diffusivities of HTO in water and HTO vapor in air (m 2 /s) f sa ( η w ) Tortuosity for diffusion in soil air e b HTO conc. in soil air (Bq/m 3 -air) c E0 , | u r | Bulk transfer coefficient for evaporation, wind speed (m/s)
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