I would like to know the difference between these CCSM4 historical runs
r1i1p1 r1i2p1 r1i2p2 r2i1p1 r6i1p1
clearly r1i1p1 r2i1p1 r6i1p1 are a three member ensemble with different initial conditions.
r1i2p1 is the same physics but something else. I thought i2 was reserved for differences in decadal predictability runs.
r1i2p2 is something different again with different physics. What is that?
Can someone explain how i2 and p2 differ from i1 and p1 for CCSM4?