NESTED GLOBAL INVERSION WITH A FOCUS ON NORTH AMERICA:
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NESTED GLOBAL INVERSION WITH A FOCUS ON NORTH AMERICA: COMPARISON WITH 1994-2003 BOTTOM-UP RESULTS IN CANADA. Jing M. Chen, University of Toronto Main Contributors: Feng Deng, Weiimin Ju, Misa Ishizawa, Gang Mo, & Ken Yuan, University of Toronto

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NESTED GLOBAL INVERSION WITH A FOCUS ON NORTH AMERICA: COMPARISON WITH 1994-2003 BOTTOM-UP RESULTS IN CANADA

Jing M. Chen, University of Toronto

Main Contributors:

Feng Deng, Weiimin Ju, Misa Ishizawa, Gang Mo, & Ken Yuan,University of Toronto

Kaz Higuchi, Douglas Chan, Doug Worthy, & Lin Huang, Environment Canada

Shamil Maksyutov, National Institute of Environmental Studies, Japan

TRANSCOM Annual Meeting, Purdue, 23-27 April 2007


Upscaling MethodologiesUsed in Fluxnet Canada/Canadian Carbon Program

1. Tall tower CO2 concentration data

Site toLandscape

2. Remote sensing and ecosystem modeling

(bottom-up)

Site toRegion

3. Atmospheric inverse modeling

(top-down)

Region and Globe


Bottom-up Modeling


Comparison of InTEC-modeled and measured NEP at various sites

sink

source

Data sources: Andy Black, Harry McCaughey, Paul Jarvis, Alan Barr, Brian Amiro, Hank Margolis


Datasets Used in Bottom-up ModelingUsing InTEC

  • Land cover 1995

  • LAI 1994

  • NPP 1994

  • Monthly Climate 1901-2003

  • Forest age map(inventory, large fire polygons, remote sensing)

  • DEM(hydrological effect on carbon)

  • Drainage class

  • Global CO2 time series

  • Nitrogen deposition (interpolated from 29 stations)

  • Soil texture and total carbon

  • Forest biomass


Chen et al. 2003, Tellus


Spatiotemporal Carbon Dynamics in Canada’s Forests and Wetlands

NBP


Chen et al., 2003, Tellus

Ju et al., 2006, Tellus.


Top-down Modeling


Nested Global Inversion System30 small regions in North America, 20 large regions for the rest of the globe (Transcom 3), and 88 CO2 stations (GlobalView)

Deng et al., 2006, Tellus


Models and Data

  • Models

    • NIES (National Institute of Environmental Studies of Japan), a transport model

    • BEPS, an ecosystem model, driven by NCEP data, linked with NIES

    • InTEC NBP results (1994-2003) for partial bottom-up constraint

  • Key Datasets

    • Globalview baseline station CO2 data + tall towers (2004 and 2005 versions)

    • Ocean carbon balance (Takahashi et al., 1997)

    • Global fields of fossil fuel emission in 1990 + national emissions in 2002


Nested Global Inversion Results(1994-2003, 30 Regions in North America and 50 Regions for the Globe)

Red: source

Green: sink

2005 version of GlobalView data

USA: -0.81 ± 0.21 PgC/y (sink)

Canada: -0.30 ± 0.18 PgC/y (sink)


Comparison of Results Using Two Versions of GlobalView Data

2005 version of GlobalView data

USA: -0.81 ± 0.21 PgC/y (sink)

Canada: -0.30 ± 0.18 PgC/y (sink)

Upper Bound

Lower Bound

2004 version of GlovalView data:

USA: -0.58 ± 0.15 PgC/y (sink)

Canada: -0.14 ± 0.14 PgC/y (sink)


Temporal Comparison Between Top-down and Bottom-up Results for Canada’s Forests and Wetlands

source

sink


Spatial Comparison between Top-down and Bottom-up Results for Canada’s Forests and Wetlands(region by region, 10 year average)

  • Issues:

  • Large uncertainty in top-down modeling

  • Old forest carbon sink

  • C & N coupling

  • Non-forest sinks

Lower bound

Upper bound

sink

source


Effect of Non-diagonal Co-varianceBased on Meteorological Conditions


Summary

  • Both bottom-up and top-down modeling results suggest that Canada’s forests and wetlands were carbon sinks on average in the period from 1994 to 2003.

  • Top-down results show much larger sinks than bottom-up results. Atmospheric CO2 data pull the surface flux strongly toward the sink direction, indicating that bottom-up sinks values are underestimated.

  • There are encouraging similarities in the temporal and spatial variation patterns between top-down and bottom-up results, indicating that this mutual constraining methodology is worth pursuing further under the Canadian Carbon Program.

Acknowledgement: Bottom-up modeling is mostly supported by FCRN,

and top-down modeling is so far supported by two CFCAS individual grants


The issue of old forest sinks

Productive forest

Non-productive forest


Spatial Comparison between Top-down and Bottom-up Results for Canada’s Forests and Wetlands(region by region, 10 year average)

After adjusting for old forests

Lower bound

Upper bound


Too Much Carbon and Nitrogen Coupling?

  • FACE: nutrient is less limiting at higher CO2 (W. Schlesinger)

  • Carbon and nitrogen are completely decoupled in LPJ (C. Prentice)

  • C & N coupling can be relaxed by allowing the soil C/N ratio to increase with CO2 (evidence?)


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