Title: 2.1. Introduction — ctsm CTSM master documentation

URL Source: https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Introduction/CLM50_Tech_Note_Introduction.html

Markdown Content:
**February 2018**

**Technical Description of version 5.0 of the Community Land Model (CLM)**

**\*Coordinating Lead Authors\***

**David Lawrence, Rosie Fisher, Charles Koven, Keith Oleson, Sean Swenson, Mariana Vertenstein**

**\*Lead Authors\***

**Ben Andre, Gordon Bonan, Bardan Ghimire, Leo van Kampenhout, Daniel Kennedy, Erik Kluzek, Ryan Knox, Peter Lawrence, Fang Li, Hongyi Li, Danica Lombardozzi, Yaqiong Lu, Justin Perket, William Riley, William Sacks, Mingjie Shi, Will Wieder, Chonggang Xu**

**\*Contributing Authors\***

**Ashehad Ali, Andrew Badger, Gautam Bisht, Patrick Broxton, Michael Brunke, Jonathan Buzan, Yanyan Cheng, Martyn Clark, Tony Craig, Kyla Dahlin, Beth Drewniak, Louisa Emmons, Josh Fisher, Mark Flanner, Pierre Gentine, Maoyi Huang, Jan Lenaerts, Sam Levis, L. Ruby Leung, William Lipscomb, Jon Pelletier, Daniel M. Ricciuto, Ben Sanderson, Jacquelyn Shuman, Andrew Slater, Zachary Subin, Jinyun Tang, Ahmed Tawfik, Quinn Thomas, Simone Tilmes, Francis Vitt, Xubin Zeng**

The National Center for Atmospheric Research (NCAR) is operated by the nonprofit University Corporation for Atmospheric Research (UCAR) under the sponsorship of the National Science Foundation. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

National Center for Atmospheric Research P. O. Box 3000, Boulder, Colorado 80307-300

**LIST OF FIGURES**

*   [Figure 2.1.1](#figure-land-processes) Land biogeophysical, biogeochemical, and landscape processes simulated by CLM (adapted from [Lawrence et al. (2011)](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/References/CLM50_Tech_Note_References.html#lawrenceetal2011) for CLM5.0).
    
*   [Figure 2.2.1](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Ecosystem/CLM50_Tech_Note_Ecosystem.html#figure-clm-subgrid-hierarchy) Configuration of the CLM subgrid hierarchy.
    
*   [Figure 2.4.1](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Radiative_Fluxes/CLM50_Tech_Note_Radiative_Fluxes.html#figure-radiation-schematic) Schematic diagram of (a) direct beam radiation, (b) diffuse solar radiation, and (c) longwave radiation absorbed, transmitted, and reflected by vegetation and ground.
    
*   [Figure 2.5.1](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Fluxes/CLM50_Tech_Note_Fluxes.html#figure-schematic-diagram-of-sensible-heat-fluxes) Schematic diagram of sensible heat fluxes for (a) non-vegetated surfaces and (b) vegetated surfaces.
    
*   [Figure 2.5.2](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Fluxes/CLM50_Tech_Note_Fluxes.html#figure-schematic-diagram-of-latent-heat-fluxes) Schematic diagram of water vapor fluxes for (a) non-vegetated surfaces and (b) vegetated surfaces.
    
*   [Figure 2.6.1](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Soil_Snow_Temperatures/CLM50_Tech_Note_Soil_Snow_Temperatures.html#figure-soil-temperature-schematic). Schematic diagram of numerical scheme used to solve for soil temperature.
    
*   [Figure 2.7.1](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Hydrology/CLM50_Tech_Note_Hydrology.html#figure-hydrologic-processes) Hydrologic processes represented in CLM.
    
*   [Figure 2.7.2](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Hydrology/CLM50_Tech_Note_Hydrology.html#figure-water-flux-schematic) Schematic diagram of numerical scheme used to solve for soil water fluxes.
    
*   [Figure 2.8.1](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Snow_Hydrology/CLM50_Tech_Note_Snow_Hydrology.html#figure-three-layer-snow-pack) Example of three layer snow pack (snl=-3).
    
*   [Figure 2.14.1](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/MOSART/CLM50_Tech_Note_MOSART.html#figure-mosart-conceptual-diagram) MOSART conceptual diagram.
    
*   [Figure 2.15.1](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Urban/CLM50_Tech_Note_Urban.html#figure-schematic-representation-of-the-urban-landunit) Schematic representation of the urban land unit.
    
*   [Figure 2.15.2](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Urban/CLM50_Tech_Note_Urban.html#figure-schematic-of-urban-and-atmospheric-model-coupling) Schematic of urban and atmospheric model coupling.
    
*   [Figure 2.15.3](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Urban/CLM50_Tech_Note_Urban.html#figure-schematic-of-thesis-urban-properties-tool) Schematic of THESIS urban properties tool.
    
*   [Figure 2.16.1](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/CN_Pools/CLM50_Tech_Note_CN_Pools.html#figure-vegetation-fluxes-and-pools) Vegetation fluxes and pools.
    
*   [Figure 2.20.1](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Vegetation_Phenology_Turnover/CLM50_Tech_Note_Vegetation_Phenology_Turnover.html#figure-annual-phenology-cycle) Example of annual phenology cycle for seasonal deciduous.
    
*   [Figure 2.21.1](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Decomposition/CLM50_Tech_Note_Decomposition.html#figure-schematic-of-decomposition-model-in-clm) Schematic of decomposition model in CLM.
    
*   [Figure 2.21.2](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Decomposition/CLM50_Tech_Note_Decomposition.html#figure-pool-structure) Pool structure, transitions, respired fractions, and turnover times for the 2 alternate soil decomposition models included in CLM.
    
*   [Figure 2.22.1](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/External_Nitrogen_Cycle/CLM50_Tech_Note_External_Nitrogen_Cycle.html#figure-biological-nitrogen-fixation) Biological nitrogen fixation as a function of annual net primary production.
    
*   [Figure 2.25.1](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Methane/CLM50_Tech_Note_Methane.html#figure-methane-schematic) Schematic representation of biological and physical processes integrated in CLM that affect the net CH4 surface flux.
    
*   [Figure 2.27.1](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Transient_Landcover/CLM50_Tech_Note_Transient_Landcover.html#figure-schematic-of-land-cover-change) Schematic of land cover change impacts on CLM carbon pools and fluxes.
    
*   [Figure 2.27.2](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Transient_Landcover/CLM50_Tech_Note_Transient_Landcover.html#figure-schematic-of-translation-of-annual-luh2-land-units) Schematic of translation of annual UNH land units to CLM plant functional types.
    

**LIST OF TABLES**

*   [Table 2.2.1](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Ecosystem/CLM50_Tech_Note_Ecosystem.html#table-plant-functional-types) Plant functional types
    
*   [Table 2.2.2](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Ecosystem/CLM50_Tech_Note_Ecosystem.html#table-plant-functional-type-canopy-top-and-bottom-heights) Plant functional type canopy top and bottom heights
    
*   [Table 2.2.3](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Ecosystem/CLM50_Tech_Note_Ecosystem.html#table-soil-layer-structure) Soil layer structure
    
*   [Table 2.2.4](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Ecosystem/CLM50_Tech_Note_Ecosystem.html#table-atmospheric-input-to-land-model) Atmospheric input to land model
    
*   [Table 2.2.5](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Ecosystem/CLM50_Tech_Note_Ecosystem.html#table-land-model-output-to-atmospheric-model) Land model output to atmospheric model
    
*   [Table 2.2.6](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Ecosystem/CLM50_Tech_Note_Ecosystem.html#table-surface-data-required-for-clm-and-their-base-spatial-resolution) Surface data required for CLM and their base spatial resolution
    
*   [Table 2.2.7](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Ecosystem/CLM50_Tech_Note_Ecosystem.html#table-physical-constants) Physical constants
    
*   [Table 2.3.1](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Surface_Albedos/CLM50_Tech_Note_Surface_Albedos.html#table-plant-functional-type-optical-properties) Plant functional type optical properties
    
*   [Table 2.3.2](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Surface_Albedos/CLM50_Tech_Note_Surface_Albedos.html#table-intercepted-snow-optical-properties) Intercepted snow optical properties
    
*   [Table 2.3.3](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Surface_Albedos/CLM50_Tech_Note_Surface_Albedos.html#table-dry-and-saturated-soil-albedos) Dry and saturated soil albedos
    
*   [Table 2.3.4](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Surface_Albedos/CLM50_Tech_Note_Surface_Albedos.html#table-spectral-bands-and-weights-used-for-snow-radiative-transfer) Spectral bands and weights used for snow radiative transfer
    
*   [Table 2.3.5](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Surface_Albedos/CLM50_Tech_Note_Surface_Albedos.html#table-single-scatter-albedo-values-used-for-snowpack-impurities-and-ice) Single-scatter albedo values used for snowpack impurities and ice
    
*   [Table 2.3.6](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Surface_Albedos/CLM50_Tech_Note_Surface_Albedos.html#table-mass-extinction-values) Mass extinction values (m2 kg-1) used for snowpack impurities and ice.
    
*   [Table 2.3.7](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Surface_Albedos/CLM50_Tech_Note_Surface_Albedos.html#table-asymmetry-scattering-parameters-used-for-snowpack-impurities-and-ice) Asymmetry scattering parameters used for snowpack impurities and ice.
    
*   [Table 2.3.8](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Surface_Albedos/CLM50_Tech_Note_Surface_Albedos.html#table-orbital-parameters) Orbital parameters
    
*   [Table 2.5.1](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Fluxes/CLM50_Tech_Note_Fluxes.html#table-plant-functional-type-aerodynamic-parameters) Plant functional type aerodynamic parameters
    
*   [Table 2.5.2](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Fluxes/CLM50_Tech_Note_Fluxes.html#table-coefficients-for-saturation-vapor-pressure) Coefficients for esatT
    
*   [Table 2.5.3](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Fluxes/CLM50_Tech_Note_Fluxes.html#table-coefficients-for-derivative-of-esat) Coefficients for the derivative of esatT
    
*   [Table 2.8.1](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Snow_Hydrology/CLM50_Tech_Note_Snow_Hydrology.html#table-meltwater-scavenging) Meltwater scavenging efficiency for particles within snow
    
*   [Table 2.8.2](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Snow_Hydrology/CLM50_Tech_Note_Snow_Hydrology.html#table-snow-layer-thickness) Minimum and maximum thickness of snow layers (m)
    
*   [Table 2.9.1](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Photosynthesis/CLM50_Tech_Note_Photosynthesis.html#table-plant-functional-type-pft-stomatal-conductance-parameters) Plant functional type (PFT) stomatal conductance parameters.
    
*   [Table 2.9.2](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Photosynthesis/CLM50_Tech_Note_Photosynthesis.html#table-temperature-dependence-parameters-for-c3-photosynthesis) Temperature dependence parameters for C3 photosynthesis.
    
*   [Table 2.11.1](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Plant_Hydraulics/CLM50_Tech_Note_Plant_Hydraulics.html#table-plant-functional-type-root-distribution-parameters) Plant functional type root distribution parameters.
    
*   [Table 2.14.1](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/MOSART/CLM50_Tech_Note_MOSART.html#table-mosart-parameters) List of parameters in the global hydrography dataset.
    
*   [Table 2.19.1](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/CN_Allocation/CLM50_Tech_Note_CN_Allocation.html#table-allocation-and-cn-ratio-parameters) Allocation and carbon:nitrogen ratio parameters
    
*   [Table 2.21.1](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Decomposition/CLM50_Tech_Note_Decomposition.html#table-decomposition-rate-constants) Decomposition rate constants for litter and SOM pools, C:N ratios, and acceleration parameters for the CLM-CN decomposition pool structure.
    
*   [Table 2.21.2](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Decomposition/CLM50_Tech_Note_Decomposition.html#table-respiration-fractions-for-litter-and-som-pools) Respiration fractions for litter and SOM pools
    
*   [Table 2.21.3](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Decomposition/CLM50_Tech_Note_Decomposition.html#table-turnover-times) Turnover times, C:N ratios, and acceleration parameters for the Century-based decomposition cascade.
    
*   [Table 2.21.4](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Decomposition/CLM50_Tech_Note_Decomposition.html#table-respiration-fractions-for-century-based-structure) Respiration fractions for litter and SOM pools for Century-based structure
    
*   [Table 2.24.1](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Fire/CLM50_Tech_Note_Fire.html#table-pft-specific-combustion-completeness-and-fire-mortality-factors) PFT-specific combustion completeness and fire mortality factors.
    
*   [Table 2.25.1](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Methane/CLM50_Tech_Note_Methane.html#table-methane-parameter-descriptions) Parameter descriptions and sensitivity analysis ranges applied in the methane model.
    
*   [Table 2.25.2](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Methane/CLM50_Tech_Note_Methane.html#table-temperature-dependence-of-aqueous-and-gaseous-diffusion) Temperature dependence of aqueous and gaseous diffusion coefficients for CH4 and O2.
    
*   [Table 2.26.1](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Crop_Irrigation/CLM50_Tech_Note_Crop_Irrigation.html#table-crop-plant-functional-types) Crop plant functional types (PFTs).
    
*   [Table 2.26.2](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Crop_Irrigation/CLM50_Tech_Note_Crop_Irrigation.html#table-crop-phenology-parameters) Crop phenology and morphology parameters.
    
*   [Table 2.26.3](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Crop_Irrigation/CLM50_Tech_Note_Crop_Irrigation.html#table-crop-allocation-parameters) Crop allocation parameters.
    
*   [Table 2.30.1](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Dust/CLM50_Tech_Note_Dust.html#table-dust-mass-fraction) Mass fraction mi , mass median diameter v, i , and geometric standard deviation g, i , per dust source mode i
    
*   [Table 2.30.2](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Dust/CLM50_Tech_Note_Dust.html#table-dust-minimum-and-maximum-particle-diameters) Minimum and maximum particle diameters in each dust transport bin j
    

**ACKNOWLEDGEMENTS**

The authors would like to acknowledge the substantial contributions of the following members of the Land Model and Biogeochemistry Working Groups to the development of the Community Land Model since its inception in 1996: Benjamin Andre, Ian Baker, Michael Barlage, Mike Bosilovich, Marcia Branstetter, Tony Craig, Aiguo Dai, Yongjiu Dai, Mark Decker, Scott Denning, Robert Dickinson, Paul Dirmeyer, Jared Entin, Jay Famiglietti, Johannes Feddema, Mark Flanner, Jon Foley, Andrew Fox, Inez Fung, David Gochis, Alex Guenther, Tim Hoar, Forrest Hoffman, Paul Houser, Trish Jackson, Brian Kauffman, Silvia Kloster, Natalie Mahowald, Jiafu Mao, Lei Meng, Sheri Michelson, Guo-Yue Niu, Adam Phillips, Taotao Qian, Jon Radakovich, James Randerson, Nan Rosenbloom, Steve Running, Koichi Sakaguchi, Adam Schlosser, Andrew Slater, Reto Stöckli, Ying Sun, Quinn Thomas, Peter Thornton, Mariana Vertenstein, Nicholas Viovy, Aihui Wang, Guiling Wang, Zong-Liang Yang, Charlie Zender, Xiaodong Zeng, and Xubin Zeng.

The purpose of this document is to fully describe the biogeophysical and biogeochemical parameterizations and numerical implementation of version 5.0 of the Community Land Model (CLM5.0). Scientific justification and evaluation of these parameterizations can be found in the referenced scientific papers ([References](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/References/CLM50_Tech_Note_References.html#rst-references)). This document and the CLM5.0 User’s Guide together provide the user with the scientific description and operating instructions for CLM.

