When using trajplot.exe to plot multiple HYSPLIT output files, we are having trouble getting trajplot to recognize output files unless they are named tdump, tdump1, tdump2, …, tdumpn. Is it necessary for the file name to contain “tdump”?

No … tdump is only the default if there is no command line argument indicating a file name, such as trajplot -z90. When you have multiple input files you need the -iargument such as trajplot -ifile1+file2. Although you may be tempted, trajplot file1+file2 will not work.

Roland Draxler