The Community Land Model Version 5: Description of New Features, Benchmarking, and Impact of Forcing Uncertainty
Модель суши сообщества, версия 5: описание новых возможностей, бенчмаркинг и влияние неопределенности данных форсинга
2019-10-19
SCID: 54.1/qj5bwpw5
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Community Land Model version 5forcing uncertaintyglobal crop modelland model benchmarkingplant hydraulics
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Abstract (AI)
Abstract The Community Land Model (CLM) is the land component of the Community Earth System Model (CESM) and is used in several global and regional modeling systems. In this paper, we introduce model developments included in CLM version 5 (CLM5), which is the default land component for CESM2. We assess an ensemble of simulations, including prescribed and prognostic vegetation state, multiple forcing data sets, and CLM4, CLM4.5, and CLM5, against a range of metrics including from the International Land Model Benchmarking (ILAMBv2) package. CLM5 includes new and updated processes and parameterizations: (1) dynamic land units, (2) updated parameterizations and structure for hydrology and snow (spatially explicit soil depth, dry surface layer, revised groundwater scheme, revised canopy interception and canopy snow processes, updated fresh snow density, simple firn model, and Model for Scale Adaptive River Transport), (3) plant hydraulics and hydraulic redistribution, (4) revised nitrogen cycling (flexible leaf stoichiometry, leaf N optimization for photosynthesis, and carbon costs for plant nitrogen uptake), (5) global crop model with six crop types and time‐evolving irrigated areas and fertilization rates, (6) updated urban building energy, (7) carbon isotopes, and (8) updated stomatal physiology. New optional features include demographically structured dynamic vegetation model (Functionally Assembled Terrestrial Ecosystem Simulator), ozone damage to plants, and fire trace gas emissions coupling to the atmosphere. Conclusive establishment of improvement or degradation of individual variables or metrics is challenged by forcing uncertainty, parametric uncertainty, and model structural complexity, but the multivariate metrics presented here suggest a general broad improvement from CLM4 to CLM5.
Key Findings
1
Benchmarking across multiple simulations, forcing datasets, vegetation states, and CLM versions uses ILAMBv2 and other metrics to evaluate model performance.
2
CLM5 introduces extensive updates to land-surface processes, including hydrology, snow, plant hydraulics, nitrogen cycling, crops, urban energy, carbon isotopes, and stomatal physiology.
3
Forcing uncertainty, parameter uncertainty, and structural complexity prevent definitive attribution of improvement or degradation for individual variables or metrics.
4
Multivariate evaluation indicates a general broad improvement from CLM4 to CLM5.
5
New optional CLM5 capabilities include demographically structured dynamic vegetation, ozone damage, and fire trace-gas emission coupling to the atmosphere.
Research Object
The Community Land Model version 5 (CLM5) as the land component of CESM used in global and regional modeling systems
Research Subject
The new land-surface processes and parameterizations in CLM5, and their simulated performance and sensitivity to forcing uncertainty
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2019-10-19
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