Technical Description of version 4.0 of the Community Land Model (CLM)

The purpose of this technical note is to describe the physical parameterizations and numerical implementation of version 4.0 of the Community Land Model (CLM4.0) which is the land surface parameterization used with the Community Atmosphere Model (CAM4.0) and the Community Climate System Model (CCSM4.0). Scientific justification and evaluation of these parameterizations can be found in the referenced scientific papers (section 18). Chapters 1-16 constitute the description of CLM when coupled to CAM or CCSM, while Chapter 17 describes processes that pertain specifically to the operation of CLM in offline mode (uncoupled to an atmospheric model). Chapters 13 and 14 provide brief overviews only of the urban and carbon-nitrogen submodels. Full technical descriptions of these submodels can be found in Oleson et al. (2010) and Thornton et al. (2010, in preparation), respectively. These technical notes and the CLM4 User's Guide together provide the user with the scientific description and operating instructions for CLM.