An example of our validation methodology is presented above. Field measurements of net primary production (NPP) have been gathered from more than 1900 sites throughout the world and scaled for "Observed NPP" to the same spatial resolution as the CASA model "Predicted NPP". The comparison below shows a close agreement between the Observed and Predicted NPP over the entire range of measurements. Predicted NPP becomes the major input variable to NASA-CASA model calculations of plant biomass carbon and soil carbon pool sizes.

This data set of more than 1900 observed NPP points was compiled for the Ecosystem Model-Data Intercomparison (EMDI) activity and the Global Primary Productivity Data Initiative (GPPDI) working groups of the International Geosphere Biosphere Program Data and Information System (IGBP-DIS).

Reference List to validation of NASA-CASA model predictions

Amthor, J. S., J. M. Chen, J. S. Clein, S. E. Frolking, M. L. Goulden, R. F. Grant, J. S. Kimball, A. W. King, A. D. McGuire, N. T. Nikolov, C. S. Potter, S. Wang, and S. C. Wofsy, 2001. Boreal forest CO2 exchange and evapotranspiration predicted by nine ecosystem process models: Inter-model comparisons and relations to field measurements. J. Geophys. Res., 106, 33,623- 33,648.

Behrenfeld, M. J., J. T. Randerson, C. R. McClain, G. C. Feldma, S. Q. Los, C. I. Tucker, P. G. Falkowski, C. B. Field, R. Frouin, W. E. Esaias, D. D. Kolber, and N. H. Pollack, 2001. Biospheric primary production during an ENSO transition. Science 291, 2594-2597.

Davidson, E. A., C. S. Potter, S. A. Klooster, and P. Schlesinger. 1998. Model estimates of regional nitric oxide emissions from soils of the southeastern United States. Ecological Applications. 8:748-759.

Hicke, J. A., G. P. Asner, J. T. Randerson, C. J. Tucker, S. O. Los, R. Birdsey, J. C. Jenkins, C. B. Field, and E. A. Holland, 2002, Satellite-derived increases in net primary productivity across North America, 1982-1998. Geophysical Research Letters. 29(10): 1427, doi:10.1029/2001GL013578.

Hicke, J. A., G. P. Asner, J. T. Randerson, C. J. Tucker, S. O. Los, R. Birdsey, J. C. Jenkins, anmd C. B. Field, 2002, Trends in North American net primary productivity derived from satellite observations, 1982-1998, Global Biogeochem. Cycles, 16 (2), 10.1029/2001GB001550.

Lobell, D. B., J. A. Hicke, G. P. Asner, C. B. Field, C. J. Tucker, and S. O. Los, 2002, Satellite estimates of productivity and light use efficiency in United States agriculture, 1982-1998. Global Change Ecology 8:722-735.

Malmström, C. M., M. V. Thompson. G. P. Juday, S. O. Los, J. T. Randerson, and C. B. Field, 1997, Interannual variation in global scale net primary production: Testing model estimates. Global Biogeochem. Cycles. 11, 367-392.

Potter, C. S., S. A, Klooster, R. B. Myneni, V. Genovese, P.-N. Tan, and V. Kumar. 2003, Continental scale comparisons of terrestrial carbon sinks estimated from satellite data and ecosystem modeling 1982-1998, Global and Planetary Change, (In Press).

Potter, C., S. Klooster, and C. Krauter, 2003, Regional modeling of ammonia emissions from native soil sources in California, Earth Interactions, (In Press).

Potter, C. S., J. Bubier, P. Crill, and P. LaFleur. 2001. Ecosystem modeling of methane and carbon dioxide fluxes for boreal forest sites. Canadian J. Forest Research. 31: 208- 223.

Potter, C. S., E. A. Davidson, D. C. Nepstad, and C. R. Carvalho. 2001. Ecosystem modeling and dynamic effects of deforestation on trace gas fluxes in Amazon tropical forests. Forest Ecology and Management. 152: 97-117.

Potter, C. S., S. Klooster, C. R. de Carvalho, V. Brooks-Genovese, A. Torregrosa, J. Dungan, M. Bobo, and J. Coughlan. 2001. Modeling seasonal and interannual variability in ecosystem carbon cycling for the Brazilian Amazon region. J. Geophys. Res. 106: 10,423-10, 446.

Potter, C. S. 1997. An ecosystem simulation model for methane production and emission from wetlands. Global Biogeochemical Cycles. 11: 495-506.

Potter, C. S., R. H. Riley, and S. A. Klooster. 1997. Simulation modeling of nitrogen trace gas emissions along an age gradient of tropical forest soils. Ecological Modeling. 97(3):179-196.

Potter, C. S. and S. A. Klooster. 1997. Global model estimates of carbon and nitrogen storage in litter and soil pools: Response to change in vegetation quality and biomass all ocation. Tellus. 49B(1):1-17.

Potter, C. S. and S. A. Klooster. 1997. Global model estimates of carbon and nitrogen storage in litter and soil pools: Response to change in vegetation quality and biomass all ocation. Tellus. 49B(1):1-17.

Schimel D, House J, Hibbard K, Bousquet P, Ciais P, Peylin P, Apps M, Baker D, Bondeau A, Brasswell R, Canadell J, Churkina G, Cramer W, Denning S, Field C, Friedlingstein P, Goodale C, Heimann M, Houghton RA, Melillo J, Moore III B, Murdiyarso D, Noble I, Pacala S, Prentice C, Raupach M, Rayner P, Scholes B, Steffen W, Wirth C, 2001. Recent patterns and mechanisms of carbon exchange by terrestrial ecosystems, Nature, 414:169-172.