Data Citation

Cite this data set as follows:

Olson, R. J., J. M. O. Scurlock, S. D. Prince, D. L. Zheng, and K. R. Johnson (eds.). 2001. NPP Multi-Biome: NPP and Driver Data for Ecosystem Model-Data Intercomparison. Data set. Available on-line [http://www.daac.ornl.gov] from the Oak Ridge National Laboratory Distributed Active Archive Center, Oak Ridge, Tennessee, U.S.A.

Summary

The Ecosystem Model-Data Intercomparison (EMDI), an on-going activity whose first workshop was held in Durham, New Hampshire, USA, in December 1999, provides the first opportunity for a wide range of global carbon cycle models to be compared with measured net primary productivity (NPP). The second EMDI workshop was held in April 2001 at the National Center for Ecological Analysis and Synthesis (NCEAS), Santa Barbara, California, U.S.A. EMDI is supported by GAIM (Global Analysis, Integration and Modelling), a component of the International Geosphere Biosphere Program (IGBP) of the International Council of Scientific Unions (ICSU). The goals of EMDI are to compare model estimates of terrestrial carbon fluxes (NPP) to estimates from ground-based measurements, and to improve understanding of environmental controls of carbon allocation. The primary questions to be addressed are to test simulated controls and model formulation on the water, carbon, and nutrient budgets with the observed NPP data providing the constraint for autotrophic fluxes and the integrity of scaled biophysical driving variables.

Twelve modeling groups participated in the first EMDI workshop, with a variety of models, including including biogeochemical, satellite-driven, detailed process, and DVGM types. Each modeling group was provided basic model drivers for the sites and regions or could use their own resources for producing model simulations. The NPP measurements were not provided to the modelers until they submitted their simulation results. The workshop focused on how well and what aspects of the measurement data the models captured (or failed to capture) with each model group comparing their model output with the EMDI data set. Part of the workshop was devoted to identifying potential errors, outliers, and harmonizing the driver data, especially land cover and vegetation type. One participant made the following observation in a summary of the Workshop: "Despite the enormous amount of work that went into preparing for this workshop - assembling the NPP data, locating and making available the site and region environmental data, performing the model simulations - there was a realization that model data comparison is an extraordinarily complex task that we are only just beginning.".

The second EMDI workshop included representatives from all but one of the original 12 models, and 7 more modeling groups worldwide. Models were re-run for a revised version of NPP data set, improved by outlier analysis and the addition of further half-degree grid cells (total 3855). Model results were compared with NPP data for individual models, and both above-ground NPP and total NPP compared to assess the models' carbon-allocation patterns.

Planning and preparation for EMDI were aided by an NCEAS Working Group and student internship under the title "Ecosystem Model-Data Intercomparison Working Group on Data - Synthesis, Formats, and Establishment of an EMDI Server Facility". Further information about this working groups is available on the Web page maintained by NCEAS.

The NPP data compiled for the EMDI workshops, together with the associated model driver data, are available as follows: Class A sites represent well-documented study sites that have complete aboveground and belowground NPP measurements; Class B sites represent more numerous "extensive" sites with less documentation and site-specific information available; Class C cells represent estimates of NPP for half-degree grid cells for which inventory, modeling, or remote-sensing tools were used to scale up the point measurements. The data consist of NPP values listed by latitude/longitude, model-driving climatology for all sites and grid cells, and other model drivers (soils, NDVI, land-cover classes).

Reference

Olson, R. J., K. R. Johnson, D. L. Zheng, and J. M. O. Scurlock. 2001. Global and Regional Ecosystem Modeling: Databases of Model Drivers and Validation Measurements. ORNL Technical Memorandum TM-2001/196. Oak Ridge National Laboratory, Oak Ridge, Tennessee, U.S.A.

Contact Information

Principal Contact: Bob Cook
ORNL Distributed Active Archive Center
Oak Ridge National Laboratory
Oak Ridge, TN 37831
U.S.A.
Tel. +1 (865) 574-7319
Email: Cookrb@ornl.gov

This work was conducted as part of the Ecosystem Model-Data Intercomparison Working Group supported by the U.S. National Center for Ecological Analysis and Synthesis, a Center funded by NSF (Grant #DEB-94-21535), the University of California at Santa Barbara, and the State of California.