This web page contains links to documentation, source code, and input
data for the stand-alone version release of CLM3.5. CLM3.5 is available
as a stand-alone model only. Support for this release is limited and does
not include porting to new platforms or coupling to CAM. This version is recommended for
experienced users only.
CLM3.5 is considerably different to CLM3.0, particularly with respect to its simulation of the hydrologic cycle. The modifications consist of new surface datasets based on Moderate Resolution Imaging Spectroradiometer (MODIS) products (Lawrence and Chase 2007), an improved canopy integration scheme (Thornton and Zimmermann 2007), scaling of canopy interception (Lawrence et al. 2007), a simple TOPMODEL-based model for surface and sub-surface runoff (Niu et al. 2005), a simple groundwater model for determining water table depth (Niu et al. 2007), and a new frozen soil scheme (Niu and Yang 2006). Theree are four additional modifications. Three of these, an improved description of soil water availability, a resistance term to reduce excessive soil evaporation, and the introduction of a factor to simulate nitrogen limitation on plant productivity, can be categorized as new or improved parameterizations from the perspective of CLM3. The other may be categorized as fixing an algorithmically defective existing parameterization (correction to snowage calculation so that snowage increases monotonically) (Dickinson et al. 2006). In the document linked below, a more complete description of these modifications are provided, including full details in Appendix A-F. The summary impacts on simulated hydrology of all the changes are being synthesized in two papers, which will be posted here upon completion.
Further details and a technical description of the changes are available here (pdf).
Additionally, a number of small problems or bugs have been corrected including a revision of RTM-subcycling and corrections to a few land-locked grid cells, a more efficient soil evaporation calculation based on PFT demand, and a fix to aggregation of LAI from high-resolution source data to CLM surface data.
Lastly, we are distributing a new forcing dataset with the new code. This dataset was derived by combining observation-based analyses of monthly precipitation and surface air temperature with intramonthly variations from the NCEP/NCAR reanalysis (Qian et al., 2006).
Dickinson, R.E. et al., 2006: The Community Land Model and it's cliamte statistics as a component of the Community Climate System Model. J. Clim., 19, w302-2324.
Lawrence, P.J., and T.N. Chase, 2007: Representing a new MODIS consistent land surface in the Community Land Model (CLM3.0), J. Geophys. Res., 112, G01023, doi:10.1029/2006JG000168.
Lawrence, D.M., P.E. Thornton, K.W. Oleson, and G.B. Bonan, 2007: The partitioning of evapotranspiration into transpiration, soil evaporation, and canopy evaporation in a GCM: Impacts on land-atmosphere interaction. J. Hydromet., 8, 862-880.
Niu, G.-Y., and Z.-L. Yang, 2006: Effects of frozen soil on snowmelt runoff and soil water storage at a continental scale, J. Hydrometeorol., 7, 937-952.
Niu, G.-Y., Z.-L. Yang, R.E. Dickinson, L.E. Gulden, 2005: A simple TOPMODEL-based runoff parameterization (SIMTOP) for use in global climate models. J. Geophys. Res., 110, doi:1029/2005JD006111.
Niu, G.-Y., Z.-L. Yang, R.E. Dickinson, L.E. Gulden, H. Su, 2007: Development of a Simple Groundwater Model for use in Climate Models and Evaluation with GRACE data. J. Geophys. Res., 12, D21101, doi:10.1029/2007JD008674.
Qian, T., A. Dai, K.E. Trenberth, K.W. Oleson, 2006: Simulation of Global Land Surface Conditions from 1948 to 2004. Part I: Forcing Data and Evaluations. J. Hydromet., 7, 953-975.
Thornton, P.E., and N.E. Zimmermann, 2007: An improved canopy integration scheme for a land surface model with prognostic canopy structure, J. Climate, 20, 3902-3923.