Just to make the point real clear, the solution given by jimmyc means that in the namelist.input file, the following parameters must be set:
sf_sfclay_physics = 2, (Revised MM5 Monin-Obukhov scheme).
bl_pbl_physics = 2, (Mellor, Jamada, Yanyic).
If you want to know more combinations of Planet Boundary Layer and Surface Layer, go to this document: http://www2.mmm.ucar.edu/wrf/users/docs/user_guide_V3/users_guide_chap5.htm
go to the "Description of the Namelist Variables" section, and check the bl_pbl_physics.