F:Vertically resolved biophysicsin ALM for the soil-plant-atmospherecontinuumGautam Bisht, William Riley, Ryan Knox

Objective

I Several recent studies havedemonstrated the need for explicitlyresolving the vertical regimes of lightand thermal within the vegetationcanopies and the surrounding airspace to accurately capturevegetation response to future climateperturbations

I Develop a rigorously verified,

Roughness sublayer in canopy

Monin Obukhov similarity theory above canopy

u(z)

(Tsunv ,Tshd

v ,zi) (Tsunv ,Tshd

v ,zi)(Ta ,qa ,zi)

H

d

vertically-resolved, soil-plant-atmosphere continuum (SPAC) modelto simulate transport of water, energy, and carbon using the multiphysics problems (MPP) framework.

ApproachThe governing equations for multi-layer SPAC model is given by:Conservation of energy in vegetation:

Cv∂Tsun

v (z)∂t

= RLnet(T

sunv , z) + RS

net−Hsunv (Tsun

v ,Ta, z)− λEsunv (Tsun

v , qa, z)

Cv∂Tshd

v (z)∂t

= RLnet(T

shdv , z) + RS

net−Hshdv (Tshd

v ,Ta, z)− λEshdv (Tshd

v , qa, z)

Conservation of energy in canopy air space:

Cpaρa∂Ta(z)∂t

= − ∂∂z

(−kCP

aρa∂Ta(z)∂z

)+ Hsun

v (Tsunv ,Ta, z) + Hshd

v (Tshdv ,Ta, z)

Conservation of mass in canopy air space:

ρa∂qa(z)∂t

= − ∂∂z

(−kρa

∂qa(z)∂z

)+ Esun

v (Tsunv , qa, z) + Eshd

v (Tshdv , qa, z)

The multi-layer SPAC model additionally needs the followingquantities:I Multi-layer shortwave radiation model that considers beam and

direct radiation in photosynthetically active and near-infrared bandsseparately.

I The wind profile within and above canopy; and vertical eddydiffusivity.

MethodologyI RS

net profile will be computed first.I Vertical velocity profile will be

computed using CAS state variablesfrom previous time step.

I Lower soil boundary condition will beused from previous time step.

I Longwave radiative transfer matrix

PFT2-CAS

PFT1-CAS

CAS-PFT2CAS-PFT1 CAS

ΔPFT1

ΔPFT2

ΔCAS

!(PFT1)

!(PFT2)

!(CAS)

PFT1

PFT2

approach of Gu (1998) to compute absorbed net longwave radiationat each vertical level in the canopy will be extended to account forsunlit and shaded leaves.

I PETSc library will be used to provide numerical solution.

Examples of MPP frameworkI Evolution of pressure and temperature for an idealized

soil–root–xylem problem.I Linear convergence of L1, L2, and L∞ error of numerical solution.

I Snow–soil–standing waterthermal model withmicrotopographic features inArctic.

I Snow redistribution results insurface Tsoil heterogeneity thatpropagates deeper in the soilcolumn.

I1D subsurface model overestimates σTsoil as compared to 2D model.

For additional information, contact:Gautam BishtSoftware Developer

LBNL(510) 486-6246gbisht@lbl.gov