Summary:

Inception of the Community Land Model (CLM)

The development of the CLM can be traced to the merging of a community-developed land model focused on biogeophysics and an effort at NCAR to expand the NCAR Land Surface Model (NCAR LSM) to include the carbon cycle, vegetation dynamics, and river routing. 

In 1996, the concept of a community-developed land component for the Community Climate System Model (CCSM) was proposed. The initial specifications drew from three existing land models: the NCAR LSM, the IAP94 model, and the Biosphere-Atmosphere Transfer Scheme (BATS). A scientific steering committee was formed to provide guidance and expertise in disciplines not well-represented in land surface models.

The specifications for the new model, designated the Common Land Model, were discussed and agreed upon in 1998. An initial code was developed and tested extensively offline at various scales, using field data from projects like PILPS, FIFE, BOREAS, and others. 

Coupled simulations using the Common Land Model and CCM3 were presented in 2000, showing major improvements in the seasonality of runoff, reduction of a summer cold bias, and snow depth. Some deficiencies were noted and subsequently addressed. The code was then delivered to NCAR for implementation into the CCSM framework, and the model was introduced to the wider modeling community in 2003.