Hi Mr.Singh,

First you have to open two .nc files in GrADS (eg: a.nc, b.nc) and let us take one variable pr.

I can give u a sample grads script (sample.gs) for doing composite.

***********************sample.gs******************

'reinit'

*open two files

'sdfopen a.nc'

'sdfopen b.nc'

* pr.1 means variable pr from file 1

* taking variable pr from file 1 (a.nc)

'set time 1jan2002'

'define x1= pr.1'

'set time 1jan2003'

'define x2= pr.1'

'set time 1jan2004'

'define x3= pr.1'

* taking variable pr from file 2 (b.nc)

'set time 1jan2005'

'define x4= pr.2'

'set time 1jan2006'

'define x5= pr.2'

'set time 1jan2007'

'define x6= pr.2'

'define composite= (x1+x2+x3+x4+x5+x6)/6.0'

'set gxout contour'

'd composite'

'quit'

***************************************************

This script may be useful for you.