Ecosystem Spatial Observation and Modeling Group Figure: Spatial distributions of the average flux of photosynthetically active radiation (PAR) in the Amazon forest region during early and middle daylight hours in years 1981 to 2002 (left) and the associated linear trend (right) as estimated from NCEP-NCAR reanalysis data. Research by this group is aimed at providing an improved capability to model and monitor terrestrial ecosystem processes and their dynamics at broad spatial scales, from regional to global. The major areas of research include vegetation-climate relations, ecosystem change detection, and estimation and monitoring of biophysical and environmental variables, and satellite data assimilation for ecosystem process modeling. Satellite remote sensing is the primary data source of this groupеs research. Research on vegetation-climate relations includes studies of the role of climatic factors in determining spatial and temporal patterns of vegetation growth and ecosystem-atmosphere CO2 exchange. Research on ecosystem change detection seeks to identify and quantify the extent and rates of change of ecosystem properties and their proximate causes, such as changes in land cover and/or changes in climate, including precipitation, snow cover, and solar radiation regimes. Satellite observations are used to estimate, map and monitor key variables such as leaf-area index (LAI) and photosynthetically active radiation (PAR). These satellite-derived data sources are combined with ecosystem process models, such as SimCYCLE, for improved accuracy in simulating the spatial and temporal variation in the storage, sources, and sinks of terrestrial carbon.