The model timing and output options available to EFDC_Explorer are shown in Figure 1. EFDC has many more output options but the majority of them have become obsolete due to the capabilities of EFDC_Explorer.

In the main frame the user must specify the time to start and end the run, along with the time stepping options. Time of Start is the Julian day, relative to the Beginning Date/Time, to begin the simulation. The Duration of Reference Period is used to define a project specific meaningful period. This is often set to 24 hours to select a 1 day long reference period. The duration of the simulation is then set by specifying the number of reference periods. The ending time is computed from the starting time and duration. See the Model Metrics section for guidance in how to select an appropriate time step.

The Dynamic Timestep Options subframe allows the user to engage auto stepping by setting the Safety Factor to a positive number >0 and <1. Generally, the safety factor ought to be less than 0.8 but some runs work with the safety factor>1 and some require a value <0.3. If set to 0 it will result in fixed time steps. It should be noted that EFDC will use multiples of the Time Step when dynamic time stepping is on, so this value should be set to one second or less. The number of Ramp-Up Loops should also be set by the user; this is the number of initial iterations for which to hold the time step to a constant value during ramp-up. The Maximum dH/dT option is ignored if set to zero, but if >0 then CALSTEP will use this additional criteria to set the dynamic timestep.

Figure 1   Timing/Linkage Tab: Model Run Timing.

The subroutine in EFDC which controls the dynamic time step is CALSTEPD.f90. In this subroutine there are four methods used to determine the time step, with the minimum of the these taken as the dynamic time. The four methods are as follows:

1) Upwind difference in momentum equations 

2) Advective check. 

3) Implicit bottom friction and rotational acceleration damping,

4) Limit rate of depth change (dH/dT).

Calendar/Julian Date Linkage

If the user wants to relate the model timing to actual calendar dates, it is required to enter a base date from which the model Julian dates will be added to compute the corresponding Gregorian date. The use of the base date and model Julian dates allow EFDC_Explorer to compare model versus data for a range of plots and statistics.

The base date is entered in the Model Simulation Start Time frame. Typically this date is the 1^st of some calendar year but this is not required, any date/time is acceptable. The user can use the J<->G button to convert Julian to Gregorian or visa-versa.

If using Microsoft Excel dates for the Julian day counter, the EFDC_Explorer base date should be set to "01-Jan-1900". This allows number formatted dates in Excel to be directly used by EFDC_Explorer without adjustment. However, a projected oriented base date is recommended to prevent large numbered Julian dates, e.g. 39234.375 (01-Jun-2007 09:00). If 01-Jan-2007 was used as the base date the corresponding Julian date is 151.375.

From release of EE7.2, when the user changes the base date, it is possible to automatically update all of the Julian timing in the model including time series, starting times, etc.
When the user resets the Beginning Date/Time as shown in Figure 2 they now have the option to see if they want to update all the timing. When the user presses Apply to All Timing a popup will ask the user to confirm whether to make changes to other timing or keep the time series time the same.

Figure 2   Base Date Updating Option.

Note that users must manually copy all the *.EE files as this stores the information regarding base date. This is different to EE70 where if the user edited the *.INP file then the *.EE file would overwrite it. Now in EE71 and later versions you can directly edit the input file and the base date is only stored in *.EE file.

It is important to be aware that selecting Apply to All Timing will not update all the calibration series files. It is the user's responsibility to update those files. However, if user puts the base date at top of series in the format (1990-01-01 0:00) then EE will allow for the change.