## Trajectory / Setup Run / Control File Format

The trajectory model input control file can be created using any text editor. However if the GUI is not being used, it would be easier to let the model create the initial file based upon standard output prompts. These are described in more detail below. When data entry is through the keyboard (a file named CONTROL is not found), a STARTUP file is created. This contains a copy of the input, and which later may be renamed to CONTROL to permit direct editing and model execution without data entry. If you are unsure as to a value required in an input field, just enter the forward slash (/) character, and the indicated default value will be used. This default procedure is valid for all input fields except directory and file names. An automatic default selection procedure is also available for certain input fields of the CONTROL file when they are set to zero. Those options are discussed in more detail below. Each input line is numbered (only in this text) according to the order it appears in the file. A number in parenthesis after the line number indicates that there is an input loop and multiple entry lines may be required depending upon the value of the previous entry.

1- Enter starting time (year, month, day, hour, {minutes optional})

Default: 00 00 00 00 {00}

Enter the two digit values for the UTC time that the calculation is to start. Use 0's to start at the beginning (or end) of the file according to the direction of the calculation. All zero values in this field will force the calculation to use the time of the first (or last) record of the meteorological data file. In the special case where year and month are zero, day and hour are treated as relative to the start or end of the file. For example, the first record of the meteorological data file usually starts at 0000 UTC. An entry of "00 00 01 12" would start the calculation 36 hours from the start of the data file. The minutes field is optional but should only be used when the start time is explicitly set to a value.

2- Enter number of starting locations

Default: 1

Simultaneous trajectories can be calculated at multiple levels or starting locations. Specification of additional locations for certain types of simulations can also be accomplished through the Special Simulations menu tab, or through manual editing of the CONTROL file and running the model outside of the GUI. When multiple starting locations are specified, all trajectories start at the same time. A multiple trajectory in time option is available through the Advanced menu through a namelist file parameter setting.

3(1)- Enter starting location (lat, lon, meters)

Default: 40.0 -90.0 50.0

Trajectory starting position in degrees and decimal (West and South are negative). Height is entered as meters above ground-level. An option to treat starting heights as relative to mean-sea-level is available through the Advanced menu through a namelist file parameter setting.

4- Enter total run time (hours)

Default: 48

Specifies the duration of the calculation in hours. Backward calculations are entered as negative hours. A backward trajectory starts from the trajectory termination point and proceeds upwind. Meteorological data are processed in reverse-time order.

5- Vertical motion option (0:data 1:isob 2:isen 3:dens 4:sigma 5:diverg)

Default: 0

Indicates the vertical motion calculation method. The default "data" selection will use the meteorological model's vertical velocity fields; other options include {isob}aric, {isen}tropic, constant {dens}ity, constant internal {sigma} coordinate, and computed from the velocity {diverg}ence.

6- Top of model domain (internal coordinates m-agl)

Default: 10000.0

Sets the vertical limit of the internal meteorological grid. If calculations are not required above a certain level, fewer meteorological data are processed thus speeding up the computation. Trajectories will terminate when they reach this level. A secondary use of this parameter is to set the model's internal scaling height - the height at which the internal sigma surfaces go flat relative to terrain. The default internal scaling height is set to 25 km but it is set to the top of the model domain if the entry exceeds 25 km. Further, when meteorological data are provided on terrain sigma surfaces it is assumed that the input data were scaled to a height of 20 km (RAMS) or 34.8 km (COAMPS). If a different height is required to decode the input data, it should be entered on this line as the negative of the height. HYSPLIT's internal scaling height remains at 25 km unless the absolute value of the domain top exceeds 25 km.

7- Number of input data grids

Default: 1

Number of simultaneous input meteorological files. The following two entries (directory and name) will be repeated this number of times. A simulation will terminate when the computation is off all of the grids in either space or time. Trajectory calculations will check the grid each time step and use the finest resolution input data available at that location at that time. When multiple meteorological grids have different resolution, there is an additional restriction that there should be some overlap between the grids in time, otherwise it is not possible to transfer a trajectory position from one grid to another.

8(1)- Meteorological data grid # 1 directory

Default: ( \main\sub\data\ )

Directory location of the meteorological file on the grid specified. Always terminate with the appropriate slash (\ or /).

9(2)- Meteorological data grid # 1 file name

Default: file_name

Name of the file containing meteorological data. Located in the previous directory.

10- Directory of trajectory output file

Default: ( \main\trajectory\output\ )

Directory location to which the text trajectory end-points file will be written. Always terminate with the appropriate slash (\ or /).

11- Name of the trajectory endpoints file

Default: file_name

The trajectory end-points output file is named in this entry line.

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