Preface to special issue on the Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA) Roni Avissar Department of Civil and Environmental Engineering, Duke University, Durham, North Carolina, USA Carlos A. Nobre Instituto Nacional de Pesquisas Espaciais, Brazil Received 4 May 2002; accepted 9 May 2002; published 11 September 2002. INDEX TERMS: 3322 Meteorology and Atmospheric Dynamics: Land/atmosphere interactions; 1833 Hydrology: Hydroclimatology; 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801); 3360 Meteorology and Atmospheric Dynamics: Remote sensing; 3304 Meteorology and Atmospheric Dynamics: Atmospheric electricity; KEYWORDS: hydrometeorology of the Amazon Basin, large-scale field experiment, biosphere-atmosphere interactions Citation: Avissar R., and C. A. Nobre, Preface to special issue on the Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA), J. Geophys. Res., 107(D20), 8034, doi:10.1029/2002JD002507, 2002. [1] The Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA) is an ongoing international research initiative lead by Brazil and was initiated in 1993. After five years of careful planing, LBA started in earnest in January 1999 with the launch of the first major atmospheric meso- scale campaign in the wet season (WetAMC) that was held jointly in Rondonia with the Tropical Rainfall Measuring Mission (TRMM) validation campaign known as TRMM- LBA. LBA has grown over the past three years to encom- pass more than 100 projects, engaging over 300 scientists and students from all Amazonian countries, North America, and Europe. Geographically, the domain of these investiga- tions covers most of the Amazonian Basin. LBA was designed to create the new knowledge needed to understand the climatological, ecological, biogeochemical, and hydro- logical functioning of Amazonia, the impact of land use change on these functions, and the interactions between Amazonia and the Earth system. LBA is centered around two major key questions that are being addressed through multidisciplinary research, integrating studies in the phys- ical, chemical, biological, and human sciences: First, how does Amazonia currently function as a regional entity? Second, how will changes in land use and climate affect the biological, chemical, and physical functions of Ama- zonia, including the sustainability of development in the region and the influence of Amazonia on global climate? [2] In LBA, emphasis is given to observations and analysis that improve the knowledge base for Amazonia in six general areas: physical climate, carbon storage and exchange, biogeochemistry, atmospheric chemistry, hydrol- ogy, and land use/land cover. The program is designed to address major issues raised by the Climate Convention. It helps provide the basis for sustainable land use in Amazonia by using data and analysis to define the present state of the system and its response to observed perturbations, comple- mented by modeling to provide insights into possible changes in the future. [3] In the physical climate component, meteorological and hydrological studies from the plot scale to Amazonia in its entirety focus on determining and understanding the spatial and temporal variations of energy and water fluxes. Variations of climate, and the responses of the Amazonian system to these variations, are being investigated on daily to seasonal timescales. The duration of LBA is planned to be long enough to allow for direct observations of interannual climate variations, including the effects of the El Nin ˜o- Southern Oscillation (ENSO) cycle. Data collected in the field program are being used to improve the representation of key dynamical processes in meteorological and climate models operating at various spatial and temporal scales. [4] The carbon storage and exchange component inves- tigates whether the undisturbed ecosystems of Amazonia function as a net carbon sink and how much carbon is lost, if any, as a result of land cover/land use changes due to the clearing of forest for agriculture and selective logging. Multiyear ground-based measurements of carbon stores and fluxes are being made at sites strategically located along gradients of land use intensity, vegetation, and cli- mate, complemented by observations from aircraft cam- paigns and by modeling. Results from ecological models are used together with a basin-wide geographic information system (GIS) to estimate Amazonia’s carbon budget. [5] The biogeochemistry component focuses on nutrient cycling and emissions of greenhouse gases from natural and secondary forests and managed lands. Observations are being made at sites strategically located along gradients of land use intensity and climate, covering a range of soil fertility and land uses. These observations, which will be carried out for a few years, help quantify fluxes of trace gases (emphasizing methane and nitrous oxide), fluxes of nutrients (including export to rivers), and changing stocks of nutrients. These data are complemented by periodic airborne observations, multi- scale inventories, and local manipulative experiments. Key JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 107, NO. D20, 8034, doi:10.1029/2002JD002507, 2002 Copyright 2002 by the American Geophysical Union. 0148-0227/02/2002JD002507$09.00 LBA 1 - 1