evaluation of land model simulations across multiple sites and multiple models: results from the...
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Evaluation of land model simulations across multiple sites and multiple models: Results from the NACP site-level synthesis effort. Peter Thornton 1 , Gautam Bisht 1 , Dan Ricciuto 1 , NACP Site-Level Synthesis Participants - PowerPoint PPT PresentationTRANSCRIPT
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Evaluation of land model simulations across multiple sites
and multiple models:Results from the NACP site-level
synthesis effort
Peter Thornton1, Gautam Bisht1, Dan Ricciuto1, NACP Site-Level
Synthesis Participants
1 Oak Ridge National Laboratory, Environmental Sciences Division and ORNL Climate Change Science Institute
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Sponsors
• NASA Terrestrial Ecology Program• DOE, Office of Biological and
Environmental Research, Climate and Environmental Sciences Division, Terrestrial Ecosystem Science Program
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Premise
• Models can and should serve as tools for the integration and synthesis of our best understanding and knowledge
• Models can and should provide testable (falsifiable) hypotheses
• Through model-data synthesis efforts, those hypotheses can and should be tested, and discarded or improved when confidence is shown to be low
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Analysis setting• Subset of sites and models from full NACP
site-level synthesis effort• Forest sites (evergreen and deciduous)• Range of climates• Models that include diurnal cycle• Carbon, sensible heat, latent heat fluxes• Diurnal cycle, seasonal cycle, interannual
variability, long-term mean• Influence of steady-state vs. transient
forcings
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12 Models and 13 Sites• CAN-IBIS• CNCLASS• CLM-CN• ECOSYS• ED2• ISOLSM• LOTEC• ORCHIDEE• SIB• SIBCASA• SSIB2• TECO
• CA-Ca1 Campbell River• CA-Oas Old aspen• CA-Obs Old black spruce• CA-Ojp Old jack pine• CA-Qfo Mature black spruce• CA-TP4 Turkey Point• US-Dk3 Duke Forest pine• US-Ha1 Harvard Forest main• US-Ho1 Howland main• US-Me2 Metolius intermediate• US-MOz Missouri Ozark• US-NR1 Niwot Ridge• US-UMB U Michigan Bio Stn
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Diurnal cycle of GPP: US-Dk3
Mean diurnal cycle for June-July-August, y-axis units = umol/m2/s, x-axis is half-hour time step. Results from steady-state simulations
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Diurnal cycle of GPP: CA-Obs
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Diurnal cycle of GPP: US-UMB
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Diurnal cycle of NEE: CA-Oas
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Diurnal cycle of NEE: US-Ha1
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Diurnal cycle of NEE: US-Dk3
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Diurnal cycle of NEE: CLM-CN
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Seasonal cycle of CLM-CN: US-Ha1
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Findings: 1
• Time-scale of N-limitation mechanism in CLM-CN is wrong.– Evident at both diurnal and seasonal– Original hypothesis that plants respond to N
availability on sub-daily time scale should be rejected
– Introducing new mechanism to buffer N availability in time
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Findings: 2
• Evaluation of LE suggests that current basis for estimation of stomatal conductance in CLM-CN is reasonable– This result should be revisited once new N
storage mechanism is added
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Findings: 3
• CLM-CN is very sensitive to fine root : leaf allocation patterns– Difficult measurement– Likely candidate parameter for data
assimilation– Evidence emerging from global-scale studies
and comparison to root turnover data that model fine root longevity needs to be modified
• Other models sensitive to this as well?
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Findings: 4 (underway)
• Introducing transient forcing (disturbance, rising atmospheric CO2, changing N deposition) seems to improve estimate of decadal-scale NEE– Doesn’t seem to change conclusions obtained
from steady-state simulations– This is the most critical flux for evaluation of
long-term climate-carbon cycle feedbacks
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Conclusions
• Approach has proved very useful in identifying strengths and weaknesses in CLM-CN
• This kind of critical evaluation across multiple models provides a path forward for improved future model generations
• Improving modelers’ ability to know what to ask for from observationalists and experimentalists.