Hi Ming,
No worries.
Setting ICLOUD = 0 gave me unintelligible error messages during compilation. Rather than try to debug them, I simply commented out the two "IF (ICLOUD .ne. 0) THEN" blocks within the RRTMG_SWRAD subroutine. That seemed to do the trick.
Bottom line is, you have to actually modify the source code - there is no way to do it in the namelist.
Thanks for your help.