Vegetation-Ecosystem Modeling and Analysis Project (VEMAP) was a large, collaborative, multi-agency program to simulate and understand ecosystem dynamics for the continental United States. The collaboration included scientists from NCAR, The University of Montana, Oregon State University, Colorado State University, The Ecosystems Center of the Marine Biological Labs, University of Virginia, Oak Ridge National Laboratory, University of Sheffield, UK, University of Lund, Sweden, and the Max-Planck-Institute for Biogeochemistry, Germany. The project involved the development of common data sets for model input including a high-resolution topographically-adjusted climate history of the United States from 1895-1993 on a 0.5º grid, with soils and vegetation cover. The vegetation cover data set includes a detailed agricultural data base based on USDA statistics and remote sensing, as well as natural vegetation (also derived from satellite imagery). The climate data set was developed at NCAR by Tim Kittel (EDAS) and Nan Rosenbloom (EDAS), with collaboration from Oregon State University (Chris Daly) and NOAA's National Climate Data Center (NCDC). Two principal model experiments were run. First, a series of ecosystem models were run from 1895 to 1993 to simulate current ecosystem biogeochemistry. Second, these same models were integrated forward using the output from two climate system models (CCCma (Canadian Centre for Climate Modelling and Analysis) and Hadley Centre models) using climate results translated into the VEMAP grid and re-adjusted for high-resolution topography for the simulated period 1993-2100.
Phase 1 (equilibrium responses) of the project was structured as a sensitivity analysis, with factorial combinations of climate (current and projected under doubled CO2), atmospheric CO2, and mapped and model-generated vegetation distributions. The highly structured nature of the intercomparison allowed rigorous analysis of results, while constraining the range of questions explored. Maps of climate, climate change scenarios, soil properties, and potential natural vegetation were prepared as common boundary conditions and driving variables for the models (Kittel et al. 1995). As a consequence, differences in model results arose only from differences among model algorithms and their implementation rather than from differences in inputs. Results from VEMAP I are reported in VEMAP Members (1995) and selected files are available through the VEMAP1 results web page.
Phase 2 (transient dynamics) compared time-dependent ecological responses of biogeochemical models and coupled biogeochemical-biogeographical models (Dynamic Global Vegetation Models, DGVMs) to historical and projected transient forcings across the conterminous United States. These model experiments were driven by historical time series and projected transient scenarios of climate and atmospheric CO2.
VEMAP was funded by NASA, Electric Power Research Institute (EPRI), USDA Forest
Service, and US Department of Energy, with additional support from the National
Equilibrium Responses - Phase 1. The first phase of the project evaluated equilibrium responses of the models to equilibrium climate change and doubled atmospheric CO2 levels across the conterminous United States.
Database. For Phase 1, the VEMAP1 Data Group at NCAR (T. Kittel and D. Schimel, PI's) generated gridded data layers of bioclimate, climate change scenarios, soil properties, and potential natural vegetation as common boundary conditions and driving variables for the models (Kittel et al. 1995 ABSTRACT, Rosenbloom and Kittel 1996 ON-LINE DOCUMENT). The set has both daily and monthly representations of the same long-term climate.
Bioclimate. In the development of the climate input data, we used spatial interpolation techniques that account for elevation and aspect along with statistical and empirical models for generating daily weather and estimating secondary variables (solar radiation, humidity) in order to maintain physical consistency among climate variables and between climate, vegetation, and topography. These techniques were implemented to generate an integrated dataset that realistically portrays the "bioclimate," i.e., those features of climate that control the distribution and function of ecosystems.The VEMAP Phase 1 Database is available on the VEMAP1 data access page, on a CDROM (Kittel et al. 1996;TO ORDER), and from the ORNL DAAC.
Model Intercomparison Results. Because the models were driven by a common dataset, differences in model results arose only from differences among model algorithms and their implementation rather than from differences in inputs.In the VEMAP model intercomparison, model-based assessments of ecological sensitivity to altered climate and CO2 were strongly dependent on model assumptions and parameterizations. Model results from VEMAP Phase 1 are reported in VEMAP Members (1995), Schimel et al. (1997), Pan et al. (1998), and Yates et al. (2000). Selected model output files are available through the VEMAP1 results web page.
Additional, more detailed analyses of VEMAP model outputs including those of the surface water budget (Hibbard et al., submitted; Cienciala et al., submitted) and LAI (leaf area index; Drapek et al., submitted) are completed.
Transient Dynamics - Phase 2. The objectives of Phase 2 were to compare time-dependent ecological responses of biogeochemical models and coupled biogeochemical-biogeographical models (Dynamic Global Vegetation Models, DGVMs) to historical and projected transient forcings across the conterminous United States. These model experiments were driven by historical time series and projected transient scenarios of climate and atmospheric CO2.
Database. The VEMAP2 Data Group at NCAR, in collaboration with the Geophysical Statistics Project at NCAR, developed the model input datasets required for Phase 2 (DESCRIPTION). These include a historical (1895-1994) gridded dataset of climate (temperature, precipitation, solar radiation, humidity, and wind speed; Kittel et al. 1997; ABSTRACT) and transient climate change scenarios based on coupled atmosphere-ocean GCM experiments, including those with elevated greenhouse gases and sulfate aerosols. ANIMATIONS
Model Intercomparison Results. The first round of VEMAP2 modeling results appeared in Science (Schimel et al. 2000; ABSTRACT). Additional analyses are in progress (Neilson et al., Running et al.).
Updated Sunday, 10-Feb-2002 12:58:00 MST Contacts