the discrepancy of two almost identical run

[huihuojia@163_com]

Hi, I haved used CESM to do the forecast in two different machines, and the compiler is ifort and xlf90 respectively. And all other sets are same, including the initial conditions. But when I check the output rainfall, I found out that the forecast accumulated ranifall are different. Is it because I may have some problems when I do the porting or it is just because the accuracy of machines?The attached are forecast results. 

 

[hannay]

"Almost identical runs" will diverge quickly due to climate variability. Alhought they are supposed to produce the same climate: i.e. if you take a 20-year climatology, the climate will be similar.