Hi Ann, Not only are you using HDF4 files, but you must also be using a version of ncdump that's part of the HDF4 software. We don't have a version of ncdump that can read or write HDF4 files. So I suggest you send this question to the THG Helpdesk at address@hidden --Russ Russ Rew UCAR Unidata Program address@hidden http://www.unidata.ucar.edu Ticket Details =================== Ticket ID: POG-667960 Department: Support netCDF Priority: Normal Status: Closed