EVALUATION OF SITE AND CONTINENTAL TERRESTRIAL CARBON CYCLE SIMULATIONS WITH NORTH AMERICAN FLUX TOWER OBSERVATIONS
Abstract
Terrestrial carbon models are widely used to diagnose past ecosystem-atmosphere carbon fluxes in response to climate variability, and are a critical component of coupled climate-carbon model used to predict global climate change. The North American Carbon Program (NACP) Interim Regional and Site Interim Synthesis activities collected a broad sampling of terrestrial carbon model results run at both regional and site level. The Regional interim synthesis activity aims to determine our current knowledge of the carbon balance of North America by comparing the flux estimates provided by the various terrestrial carbon cycle models. Moving beyond model-model comparison is challenging, however, since no continental-scale reference values exist against which to validate modeled fluxes. This paper presents an effort to evaluate the continental-scale flux estimates of these models using North American flux tower observations brought together by the Site interim synthesis activity. Flux towers present a standard for evaluation of the modeled fluxes, though this evaluation is challenging because of the mismatch in spatial scales between the spatial resolution of continental-scale model runs and the size of a flux tower footprint. We rank the models according to performance vs. flux tower observations using the statistical criteria of standard deviation, correlation coefficient and centered root mean square deviation. Models run at both site and continental scale are evaluated. As might be expected the site level model runs matched the flux tower net carbon flux observations better than the regional runs both in terms of mean annual flux magnitude and interannual variability in fluxes. Model simulation of interannual variability in net carbon flux, however, is poor even for site-level model runs in most cases. Future analyses will include evaluation of the modeled seasonal cycles, respiratory and photosynthetic fluxes, and determination of the role of spatial resolution in explaining the differences between site and regional level model-data comparisons. This work is a first step towards systematic and quantitative evaluation of the performance of continental-scale terrestrial carbon cycle models.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2009
- Bibcode:
- 2009AGUFM.B54A..05R
- Keywords:
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- 0414 BIOGEOSCIENCES / Biogeochemical cycles;
- processes;
- and modeling;
- 0428 BIOGEOSCIENCES / Carbon cycling