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Overview

The Multi-Layer Canopy Model version 1 (MLCMv1) for the Energy Exascale Earth System Model (E3SM) Land Model (ELM) resolves the micro-climate created by the vegetation canopies. ELM-MLCMv1 is based on CLM-ml v11 and uses PETSc to provide support for heterogeneous computing architectures. The performance portability of the model has been studied on NVIDIA and AMD GPUs.

The MLCMv1 has been benchmarked against the CLM-ml v1 for the Ameriflux US-Unversity of Michigan Biological Station site. The equations describing the various physics in this technical guide are based on previous publications23.

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Schematic representation of ELM-MLCMv1.

The ELM-MLCMv1 accounts for sunlit (shown in light green) and shaded (shown in dark green) leaves at each canopy level. The model includes the following four sub-models for:

  1. shortwave and longwave radiation,
  2. stomatal conductance,
  3. roughness sublayer (RSL) parameterization, and
  4. transport of heat and water vapor in the canopy air space (CAS).

The radiation model and RSL parameterization lump sunlit and shaded leaves as one at each canopy layer, while the other two sub-models explicitly account for sunlit and shaded leaves. Similar to CLM-ml v11, it is assumed that water from the soil is transported to each leaf via unconnected xylems. The vertical profiles of the leaf and stem of a plant are described using a beta distribution.

  1. Gordon B Bonan, Edward G Patton, John J Finnigan, Dennis D Baldocchi, and Ian N Harman. Moving beyond the incorrect but useful paradigm: reevaluating big-leaf and multilayer plant canopies to model biosphere-atmosphere fluxes–a review. Agricultural and Forest Meteorology, 306:108435, 2021. ↩↩

  2. Gordon B Bonan, Edward G Patton, Ian N Harman, Keith W Oleson, John J Finnigan, Yaqiong Lu, and Elizabeth A Burakowski. Modeling canopy-induced turbulence in the earth system: a unified parameterization of turbulent exchange within plant canopies and the roughness sublayer (clm-ml v0). Geoscientific Model Development, 11(4):1467–1496, 2018. ↩

  3. Gordon Bonan. Climate change and terrestrial ecosystem modeling. Cambridge University Press, 2019. ↩