## Trajectory / Display / Frequency

Multiple trajectory files can be displayed by creating an arbitrary grid over the computational domain and then counting the number of trajectory intersections over each grid point and dividing by the total number of trajectories. A trajectory may only intersect a grid point once. Each trajectory is defined by one output file which is only permitted to contain one trajectory. Trajectory output file names must begin with tdump followed by any arbitrary identification text such as might be created by the Run Daily menu option. The trajectory endpoint files should reside in the working directory. The first step in the processes is to create a file of trajectory file names which will always be called INFILE. This file may be manually edited to remove any trajectory files that are not required for the analysis. Then select the grid resolution according to the scale of the desired result. Too fine a grid with too few trajectories can result in poorly contoured results. The gridded binary output file is in the HYSPLIT concentration format. The concentration plotting routine is used to display the trajectory frequency results and hence some of the label options are inconsistent with this particular application. The trajectory frequency results could be exported to an ASCII file using one of the concentration convert utility options or displayed using one of the GIS formats.

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