The ARL web server contains several meteorological model data sets already converted into a HYSPLIT compatible format on the public directories. Direct access via FTP to these data files is "hardwired" into the GUI. Only an email address is required for the password to access the server. The "FTP menu" is locked until the FTP process is completed, at which point a message box will appear indicating the file name that was just transferred.
The ARL analysis data archive consists of output from the Global Data Analysis System (GDAS) and the NAM Data Analysis System (NDAS) covering much of North America. Both data archives are available from 1997 in semi-monthly files. The NDAS (formerly EDAS) was saved at 80-km resolution every 3-h through 2003, and then at 40-km resolution (AWIPS 212 grid) starting in 2004. The GDAS (every 6-h) was saved on a hemispheric projection at 191-km resolution.
From the GUI it is necessary to enter the year, select the month and period (001 for the 1st through the 15th and 002 for the 16th through the end of the month). The file name will be automatically created.
Note that NOAA NCEP models are run at much higher spatial resolution than what is archived in a HYSPLIT compatible format on the ARL server. If calculations using higher resolution data are required, then the original NDAS or GDAS GRIB encoded files must be obtained and converted as described in the documentation.