The land surface model (NCAR LSM version 1) is a one-dimensional model of energy, momentum, water, and CO2 exchange between the atmosphere and land, accounting for ecological differences among vegetation types, hydraulic and thermal differences among soil types, and allowing for multiple surface types including lakes and wetlands within a grid cell. Vegetation effects are included by allowing for twelve plant types that differ in leaf and stem areas, root profile, height, leaf dimension, optical properties, stomatal physiology, roughness length, displacement height, and biomass. These 12 plant types are combined to form 28 different vegetated surfaces, each comprised of multiple plant types and bare ground so that, for example, a mixed broadleaf deciduous and needleleaf evergreen forest consists of patches of broadleaf deciduous trees, needleleaf evergreen trees, and bare ground. Lakes and wetland, if present, form additional patches. Soil effects are included by allowing thermal properties (heat capacity, thermal conductivity) and hydraulic properties (porosity, saturated hydraulic conductivity, saturated matric potential, slope of retention curve) to vary as functions of percent sand and percent clay. Soils also differ in color, which affects soil albedos. Consequently, each grid cell in the domain of interest is assigned a surface type, a fraction covered by lakes, a fraction covered by wetlands, a soil texture (percent sand, percent silt, percent clay), and a soil color.Major features of the model are:
In coupling to the atmospheric model, the land surface model provides to the atmospheric model, at every time step, surface albedos (direct beam and diffuse for visible and near-infrared wavebands), upward longwave radiation, sensible heat flux, latent heat flux, water vapor flux, and surface stresses. The atmospheric model provides to the land model, at every time step, incident solar radiation (direct beam and diffuse for visible and near-infrared wavebands), incident longwave radiation, convective and large-scale precipitation, and lowest model level temperature, wind, specific humidity, pressure, and height.
A complete description of the model is provided in the documentation and user's guide.