The Common Land Model (CLM) is a modular land surface model developed by a team of scientists from various institutions. It is designed for weather forecasting and climate studies and is now available for public use and further development. The model incorporates various land surface parameterizations (LSPs) to calculate energy, water, and momentum fluxes across the land-atmosphere interface. Despite similar atmospheric forcing data and land surface parameters, different LSPs produce significantly different surface fluxes and soil wetness due to differences in process formulations and coding architectures. The CLM was developed to provide a common framework for community-driven land modeling, allowing for the exploration of new issues, reducing repetition, and facilitating the sharing of improvements. The CLM was developed through workshops and correspondence, initially aimed at providing a framework for the NCAR Community Climate System Model (CCSM). It was influenced by the Mosaic model and the Simplified Simple Biosphere Model (SSiB). The CLM combines features from three existing land models: the Land Surface Model (LSM) of Bonan, the Biosphere–Atmosphere Transfer Scheme (BATS) of Dickinson, and the Chinese Academy of Sciences Institute of Atmospheric Physics LSM (IAP94). The model has undergone several iterations and has been tested with extensive observational data, including the Global Soil Wetness Project (GSWP) data and the Land Data Assimilation System (LDAS). CLM has also been coupled with the NCAR Community Climate Model (CCM3), showing improved performance in simulating surface air temperature, annual runoff, and snow mass compared to the LSM. The CLM includes three main elements: a core single-column soil-snow-vegetation biophysical code, land boundary data, and scaling procedures for climate models. The model's modular structure allows for easy integration of components from other LSPs. CLM has been tested with various observational datasets, including the Valdai dataset and the ABRACOS dataset. The results show that CLM can realistically simulate key state variables and fluxes, with improvements in simulating soil moisture, runoff, and snow water equivalent depth. When coupled with CCM3, CLM significantly improves climate simulations of surface air temperature, runoff, and snow mass. CLM is now ready for public release and is designed to be modular, allowing for future improvements and developments. Some components, such as the runoff parameterization and biogeochemical cycle, need further refinement. The model has been supported by multiple funding agencies, including NASA, NSF, NOAA, and DOE. The development of CLM has been acknowledged by various scientific groups and institutions. The book "Weathering the Storm: Sverre Pettersen, the D-Day Forecast, and the Rise of Modern Meteorology" provides an autobiographical account of Sverre Pettersen, a key figure in the development of modern meteorology.The Common Land Model (CLM) is a modular land surface model developed by a team of scientists from various institutions. It is designed for weather forecasting and climate studies and is now available for public use and further development. The model incorporates various land surface parameterizations (LSPs) to calculate energy, water, and momentum fluxes across the land-atmosphere interface. Despite similar atmospheric forcing data and land surface parameters, different LSPs produce significantly different surface fluxes and soil wetness due to differences in process formulations and coding architectures. The CLM was developed to provide a common framework for community-driven land modeling, allowing for the exploration of new issues, reducing repetition, and facilitating the sharing of improvements. The CLM was developed through workshops and correspondence, initially aimed at providing a framework for the NCAR Community Climate System Model (CCSM). It was influenced by the Mosaic model and the Simplified Simple Biosphere Model (SSiB). The CLM combines features from three existing land models: the Land Surface Model (LSM) of Bonan, the Biosphere–Atmosphere Transfer Scheme (BATS) of Dickinson, and the Chinese Academy of Sciences Institute of Atmospheric Physics LSM (IAP94). The model has undergone several iterations and has been tested with extensive observational data, including the Global Soil Wetness Project (GSWP) data and the Land Data Assimilation System (LDAS). CLM has also been coupled with the NCAR Community Climate Model (CCM3), showing improved performance in simulating surface air temperature, annual runoff, and snow mass compared to the LSM. The CLM includes three main elements: a core single-column soil-snow-vegetation biophysical code, land boundary data, and scaling procedures for climate models. The model's modular structure allows for easy integration of components from other LSPs. CLM has been tested with various observational datasets, including the Valdai dataset and the ABRACOS dataset. The results show that CLM can realistically simulate key state variables and fluxes, with improvements in simulating soil moisture, runoff, and snow water equivalent depth. When coupled with CCM3, CLM significantly improves climate simulations of surface air temperature, runoff, and snow mass. CLM is now ready for public release and is designed to be modular, allowing for future improvements and developments. Some components, such as the runoff parameterization and biogeochemical cycle, need further refinement. The model has been supported by multiple funding agencies, including NASA, NSF, NOAA, and DOE. The development of CLM has been acknowledged by various scientific groups and institutions. The book "Weathering the Storm: Sverre Pettersen, the D-Day Forecast, and the Rise of Modern Meteorology" provides an autobiographical account of Sverre Pettersen, a key figure in the development of modern meteorology.