Evaluating the performance of the Canadian Land Surface Scheme Including Biogeochemical Cycles (CLASSIC) tailored to the pan-Canadian domain

Abstract

Canada's boreal forests and tundra ecosystems are responding to unprecedented climate change with implications for the global carbon (C) cycle and global climate. However, our ability to model the response of Canada's terrestrial ecosystems to climate change is limited and there has been no comprehensive, process-based assessment of Canada's terrestrial C cycle. We tailor the Canadian Land Surface Scheme Including Biogeochemical Cycles (CLASSIC) to Canada and evaluate its C cycling performance against independent reference data. We utilize skill scores to assess model performance against reference data alongside benchmark scores that quantify the level of agreement between the reference data sets to aid in interpretation. Our results demonstrate CLASSIC's sensitivity to prescribed vegetation cover. They also show that the addition of five region-specific PFTs improves CLASSIC's skill at simulating the Canadian C cycle. CLASSIC performs well when tailored to Canada, falls within the range of the reference data sets, and meets or exceeds the benchmark scores for most C cycling processes. New regionspecific land cover products, well-informed plant functional type (PFT) parameterizations, and more detailed reference data sets will facilitate improvements to the representation of the terrestrial C cycle in regional and global land surface models (LSMs). Incorporating a parameterization for boreal disturbance processes and explicitly representing peatlands and permafrost soils will improve CLASSIC's future performance in Canada and other boreal regions. This is an important step toward a comprehensive process-based assessment of Canada's terrestrial C cycle and evaluating Canada's net C balance under climate change.

Canada's wildfire future: climate change below a 2°C global target avoids large increases in burned area by the end of the century

“…It couples the Canadian Land Surface Scheme (CLASS; physics) [78][79][80][81] and the Canadian Terrestrial Ecosystem Model (CTEM; biogeochemistry) 64,82 . The site level performance of CLASSIC v1.0 was evaluated by Melton et al 83 , the global performance was evaluated by Seiler et al 84 , and model updates and improvements since v1.0 are detailed in Asaadi et al 85 , MacKay et al 86 , Meyer et al 87 , and Curasi et al 22,75 . We carry out simulations of the pan-Canadian domain at 0.22°spatial resolution using 14 biogeochemical plant functional types (PFTs) suitable for Canada 22 and reflective of the boreal vegetation of other circumboreal regions.…”

“…CLASSIC requires seven climate forcing variables: incoming shortwave radiation, incoming longwave radiation, air temperature, precipitation rate, air pressure, specific humidity, and wind speed (See Table S1 for details of the simulations utilizing specific forcings). For model evaluation, we use a bias-corrected forcing based upon reanalysis datasets (GSWP3-W5E5-ERA5), which is described in detail by Meyer et al 87 and Curasi et al 22,75 . It combines the 1901 -1978 portion of the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP) GSWP3-W5E5 and the 1979-2018 portion of the ERA5 time series bias corrected to match the means of the 310 overlapping period in the GSWP3-W5E5 [93][94][95][96] .…”

Implementing a dynamic representation of fire and harvest including subgrid-scale heterogeneity in the tile-based land surface model CLASSIC v1.45

“…A detailed description of model updates and improvements to CLASSIC since v1.0 that are utilized by our simulations can be found in Asaadi et al (2018), MacKay et al (2022. We carry out simulations of the pan-Canadian domain using a parameterization of the model which includes Canada-specific plant functional types (PFTs) that were developed and evaluated by Curasi et al, (2022).…”

“…The CTEM dynamic vegetation sub-model simulates photosynthetic fluxes, at a thirty-minute time step in offline simulations, and the allocation of C within live vegetation to structural and non-structural components of leaves, stems, and roots at a daily time step. CTEM also simulates daily autotrophic respiration from leaves, stems, and roots and heterotrophic respiration fluxes from litter and soil C. The pan-Canadian parameterization of CTEM utilizes fourteen biogeochemical PFTs (Curasi et al, 2022). CTEM is coupled to CLASS on a daily time step and provides CLASS with vegetation height, leaf area index, biomass, and rooting depth.…”

“…Our implementation is a modified version of approaches that use a fixed number of tiles to represent age classes within the stand and may apply to other tile-based LSMs. We build upon a version of CLASSIC tailored to the pan-Canadian domain using region-specific plant functional types (PFTs) and a 0.22º (~20 km x 20 km) common grid (Curasi et al, 2022). The age classes within the stand are represented using a variable number of sub-grid tiles of variable fractional area and subject to a user-determined maximum number of tiles available for the simulation.…”