"Impossible case2 in instratus_condensate" in CAM5 under high CO2

[jiangzhu]

Hello,My simulations using CESM1.2.2.1 CAM5 crashed under high CO2 concentration (~24x preindustrial CO2, 6832.8 ppmv) with the following error message in cesm.log: 460: Impossible case2 in instratus_condensate 460:   1.00000000000000       0.000000000000000E+000  0.000000000000000E+000 460:                     NaN                     NaN  This problem seems persistent and shows up as long as the global mean temperature reaches ~45 degC. So far, I have reproduced this model failure with 24xCO2 slab ocean (E compset) simulation under the present-day boundary conditions, and with 12xCO2 slab ocean (E compset) and fully coupled (B compset) simulations under the Eocene boundary conditions. Also, I tried to change the model timestep (ATM_NCPL: 48--> 96). The model did run further to 55°C but died again with the same error.Note that the deep time bug fixes have already been patched to the code base (I am actually using pcesm0.2_cesm1_2_2_1).Please help me look into this problem. Thank you very much! Regards,Jiang