221
calculated using the assumption of thermodynamic equilibrium between
the water adhered to the soil particle and the air in the soil air
space.
Forward direction: 0 < z < zo
1 < j < nc
energy: (A-4)
Fo*(1+KC2) 1 Fo*(1-KC2)
T,n+= + Fo*DZR*(-KC) Tj+,n + 1 + Fo*DZR*(l-K) J,
Fo*DZR*(l+KCI) dt*hfg
+ 1 + Fo*DZR* -KC1 Tj-l, Csj(1 + Fo*DZR*(1-KC1)) E
water: (A-5)
FL 1 FL)
j,n+1 = (1 + FL*DZR) J+,n + ( +FL*DR) j,n
S FL*DZR dt
(1 + FL*DZR) 0-,1 pw(1 + FL*DZR) Ej
vapor: (A-6)
1
Ejn= (1 + Fv*DZR)Pvj,n+-- Fv*vj+l,n
(1Fv)pj,n Fv*DZR*pvj- ,n+1
The equations for the lower boundary were formulated by applying a no-
flux boundary condition. This was imposed by assuming that an
imaginary node existed one grid spacing beyond the last node (j=nc).
Applying the assumption of no flux across the last node, implied that
the state variable evaluated at the imaginary node (nc+1) had the same
value as that at the node preceding the last node (nc-1). This was
substituted into the conservation equation and yielded equations A-7 to
A-9.