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Walter N. Meier, James A. Maslanik, Charles W. Fowler, and Jeffrey R. Key

1. Introduction The polar regions play an important role in the global climate due in part to the effects of sea ice and cloud cover on albedo and energy transfer. Turbulent heat fluxes during winter and solar energy absorbed by the ocean in summer are controlled largely by the open-water area and lead fraction in the ice pack, while radiative fluxes are regulated primarily by solar insolation, cloud properties, and surface albedo/emissivity. Efforts to gain a better understanding of these

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C. Potter, S. Klooster, P. Tan, M. Steinbach, V. Kumar, and V. Genovese

., 1993 ; Potter et al., 1999 ) used a normalized difference vegetation index (NDVI) to estimate FPAR, the current model version instead relies upon canopy radiative transfer algorithms ( Knyazikhin et al., 1998 ), which are designed to generate improved spatially varying FPAR products as inputs to carbon flux calculations. These radiative transfer algorithms, developed for the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the NASA Terra platform, account for attenuation of direct

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C. Potter, S. Klooster, P. Tan, M. Steinbach, V. Kumar, and V. Genovese

radiative transfer algorithms ( Knyazikhin et al. 1998 ), which are designed to generate improved spatially varying FPAR products as inputs to carbon flux calculations. These radiative transfer algorithms, developed for the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the NASA Terra platform, account for attenuation of direct and diffuse incident radiation by solving a three-dimensional formulation of the radiative transfer process in vegetation canopies. Monthly gridded composite data

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Christopher Potter, Steven Klooster, David Bubenheim, Hanwant B. Singh, and Ranga Myneni

accurate estimation of OVOC emissions on regional scales. Cutting and dehydration of plant material in crop and timber harvest areas, lawn mowing, and range land grazing are some of the major human activities that are thought to impact global OVOC emissions ( Fall, 1999 ; de Gouw et al., 1999 ). The aim of this study is to develop an approach for the first fully integrated global model to predict monthly biosphere–atmosphere fluxes of OVOC, with particular emphasis on major terrestrial vegetation

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Christopher Potter, Steven Klooster, Alfredo Huete, and Vanessa Genovese

1. Introduction Carbon is important as the basis for food and fiber supplies that sustain and shelter human populations, and as the primary energy source that fuels economies. Carbon dioxide (CO 2 ) is a major contributor to the planetary greenhouse effect and potential climate change. Effective carbon management strategies will require new scientific information about flux processes of the carbon cycle and an understanding of long-term interactions with other components of the Earth system

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Michael Keller, Ruth Varner, Jadson D. Dias, Hudson Silva, Patrick Crill, Raimundo Cosme de Oliveira Jr., and Gregory P. Asner

( Davidson et al. 2000 ). The soils of tropical forests are globally important sources of both N 2 O and NO ( Matson and Vitousek 1990 ; Davidson and Kingerlee 1997 ). Well-drained upland soils generally consume CH 4 from the atmosphere and soil moisture content regulates the flux through its control on the diffusion of CH 4 into the soil ( Crill 1991 ; Born et al. 1990 ). Tropical forest soils can change from a sink to a source of CH 4 depending upon soil moisture conditions and land use ( Keller

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Allison L. Steiner, Dori Mermelstein, Susan J. Cheng, Tracy E. Twine, and Andrew Oliphant

radiative properties in the free troposphere . Atmos. Res. , 102 , 365 – 393 . Baldocchi , D. D. , 2008 : ‘Breathing’ of the terrestrial biosphere: Lessons learned from a global network of carbon dioxide flux measurement systems . Aust. J. Bot. , 56 , 1 – 26 . Baldocchi , D. D. , and Coauthors , 2001 : FLUXNET: A new tool to study the temporal and spatial variability of ecosystem-scale carbon dioxide, water vapor and energy flux densities . Bull. Amer. Meteor. Soc. , 82 , 2415 – 2435

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Justin E. Bagley, Ankur R. Desai, Paul C. West, and Jonathan A. Foley

-cover change. Biogeophysical mechanisms directly alter the components of the surface energy balance, surface friction, and the water cycle by altering the physical properties of local vegetation. Plants mediate the exchange of momentum, heat, radiation, and moisture between Earth’s surface and the lower atmosphere. By altering land cover, the surface fluxes of radiative, latent ( L ), sensible ( H ), and kinetic energy are adjusted. In the case of a tropical forest, the deforestation of a region to

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Arindam Samanta, Bruce T. Anderson, Sangram Ganguly, Yuri Knyazikhin, Ramakrishna R. Nemani, and Ranga B. Myneni

investigation suggests that changes in individual radiative flux terms do not necessarily show such quasi-linear behavior. In particular, the outgoing TOA clear-sky longwave flux increases linearly with increasing temperatures but remains elevated even as global temperatures decrease, producing an asymmetric time trajectory ( Figure 3a ). While this asymmetric response does not necessarily impact the global mean surface temperatures (see Figure 1 ; also Bony et al. 2006 ; Stuber et al. 2001 ), it does

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Alexandrede S. Pinto, Mercedes M. C. Bustamante, Maria Regina S. S. da Silva, Keith W. Kisselle, Michel Brossard, Ricardo Kruger, Richard G. Zepp, and Roger A. Burke

. Saminêz ( Saminêz 1999 ) estimated an annual N 2 O soil emission of 0.5 kg N ha −1 yr −1 in a native cerrado and in a 5-yr-old pasture ( Andropogon gayannus ). Low N 2 O fluxes (0.2 ng N-N 2 O cm −2 h −1 ) were also measured by Nobre ( Nobre 1994 ) in a 10-yr-old pasture planted with Paspalum sp. Fluxes of NO in a 20-yr-old pasture ( Brachiaria brizantha ) of central Brazil were measured by Varella et al. ( Varella et al. 2004 ). They estimated annual emissions of 0.1 kg N ha −1 yr −1 , and the

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