Hi, dear  all I tried to run Regcm-4.1.1 from 1994100100 to  1994123118, for many times, but at each time  " NaN " appears at the 10th day, and I checked the ICPC data, as in the following, so please where is the error?  ATM variables written at    1994101000    0.000000000000000  SRF variables written at    1994101000    0.000000000000000  RAD variables written at    1994101000    0.000000000000000 SEARCH BC data for 1994101006 READY  BC from     1994101000 to 1994101006      at day =    9.0260, ktau =       5200 :  1st, 2nd time deriv of ps =  0.10750E-02 0.57503E-05,  no. of points w/convection =    2236      at day =    9.1128, ktau =       5250 :  1st, 2nd time deriv of ps =          NaN         NaN,  no. of points w/convection =       0 Thank you in advance Zeinab salah