Ed, Worth keeping an eye on this; multiple unlimited dimensions would removed some headaches? http://my.unidata.ucar.edu/content/software/netcdf/netcdf-4/index.html ...but it's two years away... A. -- Dr Alistair Adcroft http://www.mit.edu/~adcroft MIT Climate Modeling Initiative tel: (617) 253-5938 EAPS 54-1624, 77 Massachusetts Ave, Cambridge, MA, USA