how to use phys_buffer hold arrays that must persist across timesteps

[lupeng2006@hotmail_com]

Dear all
I want to add the module stratiform into BCC model (BCC is similar in scheme with CAM3)
So I shoud persist concld across timesteps
I do like this
add
call pbuf_add('CONCLD' , 'physpkg', 1,pver, 1, concld_idx)
ifld = pbuf_get_fld_idx('CONCLD')
concld => pbuf(ifld)%fld_ptr(1,1:pcols,1:pver,lchnk,itim)

but I find concld value is not the value in the last step

can you give me some advice

Thanks a lot