[gradsusr] How to use sdfwrite to get composite of data

[Martin Addi]

Hi to all
i have a land precipitation data from CRU in a .nc file but i want to
extract only the JAS(july,august and september)  from 1951-2009 within
lat. -40 20 and lon. -20 20.I want only this data and what is the
script or step i should use?Thank you.