CDO

Dear CDO users,
I have daily precipitation data of JFM,AMJ,JAS,OND for 3 years(2003,2004,2005) and I want
to merge daily data for differenr seasons, eg first day of Jan2003,2004 and 2005=JFM.
How can I do this process with CDO operator? Any Idea?

Thanks in advance

Saeed Bayat
M.A Student of Climatology
Department of Geography
Ferdowsi University of Mashhad(Iran)