The control file (CONTROL) for dispersion simulations is
configured from the Concentration / Concentration Setup
menu tab. The concentration setup layout is identical to the trajectory
menu with the exception of an additional button to set the emissions,
deposition, and concentration grid.
The Pollutant, Deposition and Grids setup button will bring up a submenu with each of
the three main options (Pollutant, Grids,
Deposition). The pollutant emission rate and deposition
must be set for each pollutant. Normally simulations are run for
one pollutant. Several independent concentration grids may be
defined for each simulation. However, they may be nested in space
or time if desired. Concentrations for each pollutant species are output
on all grid(s).
|An arbitrary 4-character field identifies each pollutant. The
emission rate is mass units per hour. The actual mass unit is not
specified, so for instance, if the units are kg, then concentration
output will be in kg/m3. Any unit is acceptable, however some
chemical conversion modules require specific units. The emission
start time can be set to any time at or after the start of the simulation. As
is true for all time units, zero’s default to the simulation start
time in the main menu. Zero for the month and non-zero values
for day and hour cause those values to be treated as relative to
the simulation start time.
|Each concentration grid must be defined. Zeros
for the grid center default to the source location. The grid spacing
is especially important in concentration computations in determining
the cell size (particles) or sampling resolution (puffs). When
multiple levels are defined, each height represents the top of
the cell (particles) or actual height (puffs). The averaging time
starts at the sampling start time. Snapshot (now) concentrations are
the average over one time step at the time interval specified and
maximum will save the maximum concentration at each grid point over
the duration of the output interval.