Table of contents
Chapter 1. Overview
Chapter 2. Radiation
Chapter 3. Turbulent diffusion and interactions
with the surface
Chapter 4. Subgrid-scale orographic drag
Chapter 5. Convection
Chapter 6. Clouds and large-scale precipitation
Chapter 7. Land suface parametrization
Chapter 8. Methane oxidation
Chapter 9. Climatological data
REFERENCES
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The surface parameterization computations are shared between the vertical
diffusion routine (VDFMAIN, see Chapter 3) and the main surface routine,
SRFMAIN. In VDFMAIN, the tile fluxes and skin temperatures are computed:
After the elimination part of the tridiagonal system of equations is computed,
the energy budget for each tile is computed before back-substition.
At the start of the model integration, the following setup routine is called
to initialize a module specific to the soicode:
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• SUSOIL. Setup routine for soil/snow/ice
constants. |
The main subroutine of the surface code (SRFMAIN) is called from CALLPAR,
with: (a) values of the surface prognostic equations at time step n, convective
and large scale rainfall and snowfall, tile evaporation, sensible and latent
heat fluxes, and temperatures, net surface longwave flux, tile net shortwave
flux as inputs; and (b) tendencies for the surface prognostic variables,
plus a comprehensive set of diagnostic arrays as outputs. SRFMAIN does a
sequence of computations and subroutine calls:
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• SRFSN. Solution of the snow energy and
water budget and computation of the next time step density and albedo
fields. Inputs: snow depth, temperature, density and albedo at the
current time step, soil temperature, shortwave and longwave radiation
fluxes, snowfall, and tile fluxes. Outputs: snow depth, temperature,
density and albedo at the next time step, meltwater flux, and basal
heat flux. |
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• SRFRCG. Computes apparent soil heat capacity,
ie including effects of soil freezing. Inputs: soil temperature and
vegetation covers. Output is volumetric heat capacity. |
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• SRFT. Solution of the soil heat budget.
Inputs: Soil temperature, soil moisture, longwave radiative flux,
snow basal heat flux, volumetric heat capacity, tile evaporation,
sensible heat flux and shortwave radiative flux. Output: Soil temperature
at the next time step. First the modified heat diffusivity, the soil
energy per unit area and the right-hand sice of the system of equations
are computed. The generalized surface tridiagonal solver, SRFWDIF,
is called to solve for the semi- implicit variable,  . The soil temperatures for the next time step are computed
at the end. |
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• SRFI. Solution of the ice heat budget.
Inputs: Ice temperature, longwave radiative flux, tile evaporation,
sensible heat flux and shortwave radiative flux. Output: Ice temperature
at the next time step. First the modified heat diffusivity, the ice
energy per unit area and the right-hand sice of the system of equations
are computed. The generalized surface tridiagonal solver, SRFWDIF,
is called to solve for the semi-implicit variable,  . The ice temperatures for the next time step are computed
at the end. |
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• SRFWL. Solution of the interception layer
water budget. Inputs: Interception layer contents, low and high vegetation
water cover, maximum capacity of the interception layer, convective
and large scale rainfall, snow evaporation of shaded snow tile, and
tile evaporation. Outputs: Interception layer at next time step, convective
and large scale throughfall and tile evaporation collected (or depleting)
the interception layer. |
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• SRFWEXC. First part of the computation
of the soil water budget, ie, computation of the coefficients of the
tridiagonal system of equations for  . This includes the partitioning of transpiration into root
extraction at the different layers and soil hydraulic coefficients
including the effect of frozen water. Inputs: Soil moisture and temperature,
convective and large-scale throughfall, snowmelt, tile evaporation,
tile evaporation collected (or depleting) the interception layer,
and snow evaporation of the shaded snow tile. Outputs: Modified diffusivity
for water, right- hand side of the tridiagonal system, and layer depths. |
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• SRFWDIF. Generalized surface tridiagonal
solver. Inputs: Values of  at the current time step, generalized modified diffusivities,
soil energy (or water) per unit area, and right-hand side of equations.
Output:  . The routine computes the coefficients on the left-hand side
of the equations and solves the equations using and LU-decomposition
and back substitution in one downward scan and one upward scan. |
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• SRFWINC. Computation of next time step
soil water. Inputs:  and current time step soil water. Output: next time step soil
water. |
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• SRFWNG. Bounded-value operator for intercepted
water (limited to non-negative values and values below or equal the
maximum contents of the interception layer) and soil water (limitted
to non-negative values and values below or equal saturation). The
"soil column" is scanned from top to bottom and the amount of water
needed to satisfy physical limits in each layer are borrowed from
the layer below. The water exchanged in this way is accounted for
as runoff. Inputs: next time step intercepted water and soil water.
Output: Bounded values of the same quantities. |
Relevant routines from the vertical diffusion code, discussed in full detail
in Chapter 3, include:
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• SUVEG. Assignment of vegetation related
constants. |
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• VDFBC. Definition of tile fractions and
related characteristics. |
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• VDFSURF. Definition of bare soil resistance,
low and high canopy resistances. |
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• VDFEXCS. Computation of aerodynamical
part of exchange coefficients for heat and moisture, including stability
computations. |
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• VDFEVAP. Computation of evapotranspiration
for each tile. |
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• VDFSFLX. Surface fluxes for each tile,
defined at time t. |
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• VDFTSK. Computation of the tile skin
temperatures, as a the solution of the tile energy balance. |
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• VDFTFLX. Computation of the tile fluxes
at time t + 1. |
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