Abstract. The goal of the Boreal Ecosystem-Atmosphere Study (BOREAS) is to improve our understanding of the interactions between the boreal forest biome and the atmosphere in order to clarify their roles in global change. This overview paper describes the science background and motivations for BOREAS and the experimental design and operations of the BOREAS 1994 and BOREAS 1996 field years. The findings of the 83 papers in this journal special issue are reviewed. In section 7, important scientific results of the project to date are summarized and future research directions are identified. IntroductionPersuasive arguments indicate that there will be global warming resulting from the continuing increase in atmospheric CO 2 concentration [Houghton et al., 1995; Hasselmann, 1997].However, there are uncertainties about the magnitude and regional patterns of projected global change because of shortcomings in the atmospheric general circulation models (AGCMs) used for climate simulation. There is a real need to improve (1) our understanding of basic climatic physical and dynamic processes so that we can enhance the realism and accuracy of AGCMs and (2) our ability to quantify global-scale climate variables and parameters to better initialize and vali- The exchanges of energy, water, and carbon between the atmosphere and the continents represent the lower boundary condition for the atmospheric physical climate system and the climatic forcing to terrestrial biota and biogeochemical cycles.• •øCanada Center for Remote Sensing, Ottawa.• •Atmospheric Sciences Resource Center, Albany, New York.•2University of Edinburgh, Edinburgh, Scotland.•3University of Wisconsin, Madison.•4Forestry Canada, Edmonton, Alberta, Canada.•5Atmospheric Environment Service, Downsview, Ontario, Canada.•'NASA Headquarters, Washington, D.C.

The Boreal Ecosystem Atmosphere Study (BOREAS) is a largescale international field experiment that has the goal of improving our understanding of the exchanges of radiative energy, heat, water, C02, and trace gases between the boreal forest and the lower atmosphere. An important objective of BOREAS is to collect the data needed to improve computer simulation models of the processes controlling these exchanges so that scientists can anticipate the effects of global change. From August 1993 through September 1994, a continuous set of monitoring measurements-meteorology, hydrology, and satellite remote sensing-were gathered overthe 1000 x 1000 km BOREAS study region that covers most of Saskatchewan and Manitoba, Canada. This monitoring program was punctuated by six campaigns that saw the deployment of some 300 scientists and aircrew into the field, supported by 11 research aircraft. The participants were drawn primarily from U.S. and Canadian agencies and universities, although there were also important contributions fjom France, the United Kingdom, and Russia. The field campaigns lasted for a total of 123 days and saw the compilation of a comprehensive surfaceatmosphere flux dataset supported by ecological, trace gas, hydrological, and remote sensing science observations. The surface-atmosphere fluxes of sensible heat, latent heat, C02, and momentum were measured using eddy correlation equipment mounted on a surface network of 10 towers complemented by four

Abstract:The combination of LiDAR and optical remotely sensed data provides unique information about ecosystem structure and function. Here, we describe the development, validation and application of a new airborne system that integrates commercial off the shelf LiDAR hyperspectral and thermal components in a compact, lightweight and portable system. Goddard's LiDAR, Hyperspectral and Thermal (G-LiHT) airborne imager is a unique system that permits simultaneous measurements of vegetation structure, foliar spectra and surface temperatures at very high spatial resolution (~1 m) on a wide range of airborne platforms. The complementary nature of LiDAR, optical and thermal data provide an analytical framework for the development of new algorithms to map plant species composition, plant functional types, biodiversity, biomass and carbon stocks, and plant growth. In addition, G-LiHT data enhance our ability to validate data from existing satellite missions and support NASA Earth Science research. G-LiHT's data processing and distribution system is designed to give scientists open access to both low-and high-level data products (http://gliht.gsfc.nasa.gov), which will stimulate the community development of synergistic data fusion algorithms. G-LiHT has been used to collect more than OPEN ACCESSRemote Sens. 2013, 5 4046 6,500 km 2 of data for NASA-sponsored studies across a broad range of ecoregions in the USA and Mexico. In this paper, we document G-LiHT design considerations, physical specifications, instrument performance and calibration and acquisition parameters. In addition, we describe the data processing system and higher-level data products that are freely distributed under NASA's Data and Information policy.

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