The Community Land Model Version 5: Description of New Features, Benchmarking, and Impact of Forcing Uncertainty

• Published in: Journal of Advances in Modeling Earth Systems
• Main Authors: Lawrence, David M., Fisher, Rosie A., Koven, Charles D., Oleson, Keith W., Swenson, Sean C., Bonan, Gordon, Collier, Nathan, Ghimire, Bardan, van Kampenhout, Leo, Kennedy, Daniel, Kluzek, Erik, Lawrence, Peter J., Li, Fang, Li, Hongyi, Lombardozzi, Danica, Riley, William J., Sacks, William J., Shi, Mingjie, Vertenstein, Mariana, Wieder, William R., Xu, Chonggang, Ali, Ashehad A., Badger, Andrew M., Bisht, Gautam, van den Broeke, Michiel, Brunke, Michael A., Burns, Sean P., Buzan, Jonathan, Clark, Martyn, Craig, Anthony, Dahlin, Kyla, Drewniak, Beth, Fisher, Joshua B., Flanner, Mark, Fox, Andrew M., Gentine, Pierre, Hoffman, Forrest, Keppel-Aleks, Gretchen, Knox, Ryan, Kumar, Sanjiv, Lenaerts, Jan, Leung, L. Ruby, Lipscomb, William H., Lu, Yaqiong, Pandey, Ashutosh, Pelletier, Jon D., Perket, Justin, Randerson, James T., Ricciuto, Daniel M., Sanderson, Benjamin M.
• Format: Report
• Language: English
• Published: AMER GEOPHYSICAL UNION 2019
• Subjects: global land model; Earth System Modeling; carbon and nitrogen cycling; hydrology; benchmarking; WATER-USE EFFICIENCY; DROUGHT DECIDUOUS PHENOLOGY; NET PRIMARY PRODUCTIVITY; CARBON USE EFFICIENCY; GLOBAL SOIL-MOISTURE; EARTH SYSTEM MODEL; ICE-SHEET MODEL; INTERCOMPARISON PROJECT; DATA ASSIMILATION; NITROGEN-CYCLE; Meteorology & Atmospheric Sciences; Ice Sheet
• Online Access: http://ir.imde.ac.cn/handle/131551/33914; https://doi.org/10.1029/2018MS001583

The Community Land Model (CLM) is the land component of the Community Earth System Model (CESM) and is used in several global and regional modeling systems. In this paper, we introduce model developments included in CLM version 5 (CLM5), which is the default land component for CESM2. We assess an ensemble of simulations, including prescribed and prognostic vegetation state, multiple forcing data sets, and CLM4, CLM4.5, and CLM5, against a range of metrics including from the International Land Model Benchmarking (ILAMBv2) package. CLM5 includes new and updated processes and parameterizations: (1) dynamic land units, (2) updated parameterizations and structure for hydrology and snow (spatially explicit soil depth, dry surface layer, revised groundwater scheme, revised canopy interception and canopy snow processes, updated fresh snow density, simple firn model, and Model for Scale Adaptive River Transport), (3) plant hydraulics and hydraulic redistribution, (4) revised nitrogen cycling (flexible leaf stoichiometry, leaf N optimization for photosynthesis, and carbon costs for plant nitrogen uptake), (5) global crop model with six crop types and time-evolving irrigated areas and fertilization rates, (6) updated urban building energy, (7) carbon isotopes, and (8) updated stomatal physiology. New optional features include demographically structured dynamic vegetation model (Functionally Assembled Terrestrial Ecosystem Simulator), ozone damage to plants, and fire trace gas emissions coupling to the atmosphere. Conclusive establishment of improvement or degradation of individual variables or metrics is challenged by forcing uncertainty, parametric uncertainty, and model structural complexity, but the multivariate metrics presented here suggest a general broad improvement from CLM4 to CLM5.