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Description
of Major Subroutines of the UCLA
Atmospheric Chemistry Model
Subroutine
Name(s) |
Subroutine
Description |
CHEM_INIT0
CHEM_INIT1 |
Allocation
of data structures used by the ACM and read initial distribution
of chemical specials and reactions |
MAINDATA
|
Setup
of ACM constants ******* the values for basic parameters ******* G = GRAVITY: CM SEC**-2; REARTH = EQUATORIAL RADIUS OF EARTH,CM BK = BOLTZMANN"S CONSTANT, ERG DEG K**-1 BK = 1.381d0x10**23 J/K IF NECESSARY. SBK = STEPHAN-BOLTZMANN CONSTANT, WATTS/M**2-K**4 AVG = AVOGADRO"S NUMBER,MOL**-1 ALOS = LOSCHMIDT'S NUMBER, MOLECULES CM**-3 STP AM = MOLECULAR WEIGHT OF AIR; RGAS = GAS CONSTANT, ERG DEG K**-1 MOL**-1 RGAS2 = GAS CONSTANT, L-ATM/MOLE-K SCDAY = SECONDS PER DAY HPLANCK = PLANCK'S CONSTANT (JOULES-SEC) CSPEED = SPEED OF LIGHT *********************************************************************** |
READER |
This subroutine opens all data files and reads data from m.dat |
READCHEM
|
called by READER, reads all the chemistry species and concentrations |
READ_SFLUX |
Reads the initial atmospheric fluxes |
RADDATA
|
Reads constant parameters used in radiation calculations |
RPHOTDATA |
Reads constant parameters used in the photochemistry |
CHEMSTEP
|
Main
driver routine for the chemistry step. This is call after
the initialization is completed. |
CHEMPROC
|
This
subroutine defines the grid first also updates the time
and the photodissociation rates, then divides the grid-domain
(1-dimension or 3-dimension into blocks of grid-cells and
calls the gas-phase solvers for each grid-block. |
RADPROC |
Controls the calling radiation codes |
RSUN |
Calculates
the angular distance of the sun on the ecliptic, solar flux,
sunrise and sunset time for each day |
RRADTRAN |
Driver
Routine. Defines basic atmospheric properties. This routine
is case dependent and will have to be replaced by the user
|
CALCRATE |
This subroutine calculates kinetic reaction and photorates (S-1, CM3 S-1, OR CM6 S-2) and pressure and temperature-dependence for gas-phase chemical reactions. The routine can also be modified to calculate kinetic and photorates (S-1 L MOLE-1 S-1, AND L**2 MOLE-2 S-1) for aqueous chemistry. |
SMVGEAR |
SMVGEAR
is a GEAR-type code that solves first-order ordinary differential
equations with initial value boundary conditions. In sum,
this program includes special treatment of sparse matrices
and vectorizes around grid-blocks, which are groups of grid-cells
in the overall grid-domain. Furthermore, while this program
is optimized for multiple grid-cell problems on cray-type
machines, it can be used for zero-dimensional problems (i.e.
one grid-cell) or on other vector or non-vector machines
this version includes re-ordering of grid-cells prior to
each time-interval. the purpose of the reordering is to
group cells with stiff equations together and those with
non-stiff equations together. this reordering can save signifcant
computer time (e.g. speed the code by a factor of two or
more), depending on the variation in stiffness throughout
the grid-domain. when the stiffness is the same throughout
the grid-domain (e.g. if all concentrations and rates are
the same), then re-ordering is unnecessary and will not
speed solutions. additional reordering steps can be taken
at sunrise if the zenith angle is different in each grid-cell.
one way to reorder at sunrise is to group all cells in blocks
in order of decreasing to increasing time of sunrise. many
other possibilities exist. |
SOLVECHEM
|
In this subroutine, future species concentratiions are calculated with a new method, called multistep implicit-explicit (mie). First, each species concentration is predicted with backward Euler calculation: Cestimate(t+1) = (C(t) + PROD x Dt) / (1. + loss x Dt ) and the estimated values are used in an explicit, mass conserving forward euler,calculation to predict a final VALUE: Cfinal(t+1) = C(t) + (PROD - LOSS) * Dt If Cfinal for a species is negative, then Cestimate(t+1) is recalculated for all species using new production |