When running with CN, it is critical to begin with initial conditions hat are provided with the release or to spin the model up following the CN spinup procedure before conducting scientific runs (see the Section called Spinning up the biogeochemistry Carbon-Nitrogen Model (CN spinup) in Chapter 4. Simulations without a proper spinup will effectively be starting from an unvegetated world. See the Section called Setting Your Initial Conditions File in Chapter 1 for information on how to provide initial conditions for your simulation.
Initial condition files are provided for fully coupled BCN and offline ICN cases for 1850 and 2000 at finite volume grids: 1deg (0.9x1.25), 2deg (1.9x2.5), and T31 resolutions. We also have interpolated initial conditions for BCN for 1850 and 2000 for two finite volume grids: 10x15, 4x5 and two HOMME grids (ne30np4 and ne120np4). There's also an initial condition file for ICN with the prognostic crop model for 2000 at 2deg resolution, and one with CLMSP for 2000 at 2deg resolution. We also have initial conditions for offline CNDV for 1850. The 1850 initial condition files are in 'reasonable' equilibrium. The 2000 initial condition files represent the model state for the year 2000, and have been taken from transient simulations. Therefore, by design the year 2000 initial condition files do not represent an equilibrium state. Note also that spinning the 2000 initial conditions out to equilibrium will not reflect the best estimate of the real carbon/nitrogen state for the year 2000.
Users can generate initial condition files at different resolutions by using the CLM tool interpinic to interpolate from one of the provided resolutions to the resolution of interest. Interpolated initial condition files may no longer be in 'reasonable' equilibrium.
Aerosol deposition is a required field to CLM4 sent from the atmosphere model. Simulations without aerosol deposition will exhibit unreasonably high snow albedos. The model sends aerosol deposition from the atmospheric model (either CAM or DATM). When running with prescribed aerosol the atmosphere model will interpolate the aerosols from 2-degree resolution to the resolution the atmosphere model is running at.