The APSIM Time Clock Module (Clock)

Description

The APSIM Clock module has been developed to replace the functionality of progressing through time that was previously contained in the simulation engine and weather file. Encapsulation of this important simulation concept will allow future flexibility in the specification of time and progress through it.

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Operation

The APSIM Time Clock module is operated in a way similar to other APSIM modules.

The specification of this module in the simulation control file, and its parameters in the parameter files follow normal APSIM module protocols.

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Parameter file settings

The APSIM Clock Module requires parameters to specify the time frame of the required simulation. The user must specify the beginning and the ending of the period of time that is to be simulated.

The settings available to the user are as follows:-

Note that if no simulation start or end date is specified, the entire period of the met file will be simulated.

The number implementation is only valid for dates in the Gregorian calender (after 15 October 1582), based on the algorithm by Fliegel & van Flandern in C.ACM vol.11 (oct,1968) P.657

AN EXAMPLE

The control file would require a specification such as

[apsim.sample simulation]

module = clock sample.par[all_treatments] %apsuite\apsim\clock\clock.ini[standard]

module = report sample.par[all_treatments]

.

.

The file “sample.par” could then have the following sections:-

[all_treatments.clock.parameters]

start_date = 1/1/1988

end_date = 31/12/1988

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Module Output Variables

The APSIM Time Clock Module can provide the values of several state variables for

reporting to an output file or use by other modules.

† This assumes a 52 week year with the duration of each week is adjusted so that the first

week starts on 1 st of January and the last week ends on the 31st of December.

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Using Sub-Daily Timesteps

It is possible to use timesteps to one minute in resolution within the current APSIM framework with the following constraints.

1. The timestep is constant throughout the simulation
2. The timestep is a factor of 1440 mins/day (rational fraction of one day)
3. The met file contains data at the same timestep resolution for all days within the simulation period
4. The simulation will start at the beginning of a day and finish at the end of a day
5. It is the user's responsibility to ensure that all modules with the simulation are both capable and appropriately configured to operate on these timesteps.

[all_treatments.clock.parameters]

start_date = 1/1/1988       ! simulation starting date

end_date = 31/12/1988       ! simulation ending date

timestep = 60 (min)         ! simulation timestep

The example above will specify the clock to step through the simulation essentially with 24 tick cycles per day. There is no thorough testing for synchrony of modules though some modules will give error messages if they perceive possible timestep errors.

If the timestep parameter is not specified the clock module will default to a timestep of 1 day (1440 mins), that is, one tick cycle per day.

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Events

The clock module produces several events that can be useful, particularly when using the TRACKER module.

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