Cloud effective radius air not calculated in Morrison 2 Moments Scheme. If you definitely need it in this scheme, you will need to modify the code to calculate it.
As an alternative, if you can run with the Morrison 2 Moments with consideration of CESM-NCSU RCP4.5 climatological aerosol (mp_physics=40), then the cloud effective radius is available in this scheme.
Hope this is helpful for you.
Thank you so much. It helps me. But as you told I need mp_physics 10 specifically. It would be great help if you could share some documents how to change the code if it's available. Or please explain the steps if possible