Quoted from: https://www.csm.ornl.gov/chammp/pccm2.1/doc/node2.html
CCM0B was followed with CCM1 in July of 1987 and included a similar set of detailed technical documentation [40] [5] [4] [43] [16]. Substantial changes were incorporated in the radiation scheme, including a new solar albedo parameterization accounting for the solar zenith-angle dependence of albedo on various surface types, improvements to the absorption of solar radiation by HO and O, improvements to the long wave absorptance algorithms for HO, CO and O, changes to account for the liquid water content of stratiform clouds in determining their emissivity, and incorporation of a new finite-difference scheme in the long wave part of the radiation model (see [22]). The vertical finite-difference approximations were modified to conserve energy without adversely affecting the model simulations, and frictional heating was included so that the momentum diffusion produced a corresponding heating term in the thermodynamic equation. The latter two improvements resulted in the energy in the model being conserved to the order of one W m and moisture to one-hundredth W m energy equivalent over 90-day periods. The horizontal diffusion was modified to a form in the troposphere and included a partial correction for evaluating the operator on pressure surfaces rather than sigma surfaces. The local moisture adjustment was generalized to provide for a global horizontal borrowing [30] in a conserving manner. The vertical diffusion was converted to a nonlinear form for which the eddy-mixing coefficient depended on local shear and stability. The diffusion was applied throughout the atmosphere rather than only below 500 mb as done in CCM0B, which eliminated the need for a dry convective adjustment in the troposphere. The surface drag coefficient was made a function of stability following Deardorff [8] and the equation of state was modified to formally account for moisture in the atmosphere (i.e., virtual temperature was used where appropriate and the variation with moisture of the specific heat at constant pressure was accounted for). In addition to the above changes to the physics, CCM1 included new capabilities such as a seasonal mode in which the specified surface conditions vary with time, and an optional interactive surface hydrology [7] which followed the formulation presented by Manabe [24]. Since the CCM1 could also be used as a global forecast model, codes to prepare initial data in the CCM history tape format from analyzed observed atmospheric data, such as FGGE Level IIIb analyses [25], and codes to perform nonlinear normal mode initialization [13] [12] were made available.