Managed by UT-Battelle for the Department of Energy Estimating the North American Carbon Balance Using Inter-Comparison Among Inversions, Regional Terrestrial Biogeochemistry Models, and Observational Data Wilfred Post, Deborah Huntzinger, Kenneth Davis, Brett Raczka, Daniel Hayes, Anna Michalak, Yaxing Wei, Andrew Jacobson , Robert Cook, and North American Carbon Program Regional- Interim Synthesis Participants
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Managed by UT-Battellefor the Department of Energy
Estimating the North American Carbon Balance
Using Inter-Comparison Among Inversions, Regional Terrestrial Biogeochemistry Models, and Observational
Data
Wilfred Post, Deborah Huntzinger, Kenneth Davis, Brett Raczka, Daniel Hayes, Anna Michalak, Yaxing Wei,
Andrew Jacobson , Robert Cook, and North American Carbon Program Regional-
Interim Synthesis Participants
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North America Carbon Program Synthesis Objectives Utilize new and emerging NACP research findings to
develop a picture of the current state of the North America carbon cycle
Identify continental scale carbon sources/sinks Characterize continental scale inter-annual variation Assess our capability of modeling and measuring
large scale carbon cycle dynamics
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Data sets assembled and regridded for comparison with models MODIS monthly GPP, annual NPP Soil C from surveys Inventory based C pool and flux estimates
– Forest biomass from inventory– Crop NPP from crop yield data
Comparison with eddy flux – crossover model runs with Site Synthesis
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Participating Models
19 TBMs Models differ in:
– Prognostic versus diagnostic– Driver data– Vegetation and soil properties– Photosynthetic formulation– # of carbon pools, soil carbon decomposition dynamics– Processes included, etc.
25 Inverse Models– 20 models with TRANSCOM results– 8 models with post-TRANSCOM results resolved to 1x1
degree
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TBM Model Net Flux for North America
Across model mean net flux; 2000-2005
NEP = 0.66 PgC/yr (1.8 to -0.25 PgC/yr)
NPP = 9.2 PgC/yr (6.2 to 13.8 Pg C/yr)
GPP = 18.4 PgC/yr (9.9 to 31.7 Pg C/yr)
Rh = 8.6 PgC/yr (5.8 to 13.1 Pg C/yr)
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Long-term Mean Summer (June, July, August) Net Ecosystem Productivity
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Can we diagnose the reasons for the lack of consensus in TBM performance? Driver data Photosynthesis formulation Phenology Decomposition – N limitation Regional differences Missing important processes
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Crossover Models - Regional model runs are more positively biased for GPP. Site model runs closer to observations.
Raczka et al. (in preparation)
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Long-Term Mean NEE – TBMs and Inversions
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Net NPP over U.S. Agricultural Lands:Models Compared to NASS Inventory-Based Data
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Net NPP Spatial Pattern Over U.S. Agricultural Lands: Models Compared to NASS Inventory-Based Data
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Inventory – Model Comparison
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Data Sources Years of Data Location Fluxes and Pools Available Source
U.S. Forest (FIA / CCT) 2000 – 2006 Continental U.S. plus Alaska (n = 49) NEE, VegC Smith & Heath
U.S. Croplands 2000 – 2005 Continental U.S. (n = 49) NEE, NPP West et al.
Mexico 2000 - 2005 Mexico (n = 32) NEE, VegC, Fire Emissions deJong et al. 2010
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Accounting for Lateral Fluxes
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CO 2 CO 2
Residu
e
VEGC
SOILC
Harvest
LivestockC
CH4
HumanC
CH4
Consumption
Imports – Exports
Land Use Change
PRODC
Fire RH
NPP
Fire
NEE
Grasslands /
Settlements
CO
2 U
ptake
CO
2 R
elea
se
NEEForest / Cropland
Sector“Other” Lands Sector
Export
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INVE
NTO
RY
DA
TA
TOTAL FORESTLAND CROPLAND OTHER LANDSFO
RW
AR
D
MO
DEL
SIN
VER
SE
MO
DEL
S
Mean average annual NEE (Tg C yr-1), 2000 to 2006
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Summary Regional TBM comparisons indicate a lack of
consensus for NEP and component fluxes – GPP, Ra, Rh
Analyses to diagnose the causes reveal:– Model formulation plays a significant role.– Different weather driver data sets greatly impact
GPP TBM Re tends to be tightly related to GPP –
this dampens the NEE seasonal cycle and IAV
Annual NEE cycle amplitude is small for TBM compared to inversions.
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Conclusions Regional C modeling enterprise needs a more rigorous
approach to development and evaluation. Large disparities remain in estimates based on temporal and
spatial extrapolations of experimental and site based understanding.
Additional data, especially based on spatially extensive measurements, needs to be integrated into the modeling system approach.– Improve model algorithms/parameters– Improved diagnostic and predictive usefulness– Evaluate model skill– Develop useful benchmarks
An transition from data-poor to data-rich approach is emerging for developing multi-stream observing systems and modeling system analyses.
The NACP regional synthesis has contributed by exploring how a wider range of data sources can be used.
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Next Steps
RECCAP– If you have model results for 1990-2008 we would
be interested in incorporating them into the North American RECCAP chapter.