Direct observations of the effects of aerosol loading on net ecosystem CO2 exchanges over different landscapes

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Read Full Article (file size: 206703 bytes) Cited by GEOPHYSICAL RESEARCH LETTERS, VOL. 31, L20506, doi:10.1029/2004GL020915, 2004 Direct observations of the effects of aerosol loading on net ecosystem CO₂ exchanges over different landscapes Dev Niyogi Department of MEAS, North Carolina State University, Raleigh, North Carolina, USA Hsin-I Chang Department of MEAS, North Carolina State University, Raleigh, North Carolina, USA V. K. Saxena Department of MEAS, North Carolina State University, Raleigh, North Carolina, USA Teddy Holt Department of MEAS, North Carolina State University, Raleigh, North Carolina, USA Kiran Alapaty University of North Carolina at Chapel Hill, Raleigh, North Carolina, USA Fitzgerald Booker USDA-ARS Air Quality–Plant Growth and Development Unit, Raleigh, North Carolina, USA Fei Chen National Center for Atmospheric Research, Boulder, Colorado, USA Kenneth J. Davis Department of Meteorology, Pennsylvania State University, University Park, Pennsylvania, USA Brent Holben NASA Goddard Space Flight Center, Greenbelt, Maryland, USA Toshihisa Matsui Department of Atmospheric Science, Colorado State University, Fort Collins, Colorado, USA Tilden Meyers Atmospheric Turbulence and Diffusion Division, National Oceanic and Atmospheric Administration, Oak Ridge, Tennessee, USA Walter C. Oechel San Diego State University, San Diego, California, USA Roger A. Pielke Sr. Department of Atmospheric Science, Colorado State University, Fort Collins, Colorado, USA Randy Wells Department of Crop Science, North Carolina State University, Raleigh, North Carolina, USA Kell Wilson Atmospheric Turbulence and Diffusion Division, National Oceanic and Atmospheric Administration, Oak Ridge, Tennessee, USA Yongkang Xue Department of Geography, University of California, Los Angeles, Los Angeles, California, USA Abstract We present the first direct, multisite observations in support of the hypothesis that atmospheric aerosols affect the regional terrestrial carbon cycle. The daytime growing season (summer) CO₂ flux observations from six sites (forest, grasslands, and croplands) with collocated aerosol and surface radiation measurements were analyzed for high and low diffuse radiation; effect of cloud cover; and effect of high and low aerosol optical depths (AOD). Results indicate that, aerosols exert a significant impact on net CO₂ exchange, and their effect may be even more significant than that due to clouds. The response appears to be a general feature irrespective of the landscape and photosynthetic pathway. The CO₂ sink increased with aerosol loading for forest and crop lands, and decreased for grassland. The cause for the difference in response between vegetation types is hypothesized to be canopy architecture. Received 5 July 2004; accepted 29 September 2004; published 29 October 2004. Index Terms: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801); 0315 Atmospheric Composition and Structure: Biosphere/atmosphere interactions; 0345 Atmospheric Composition and Structure: Pollution—urban and regional (0305); 1610 Global Change: Atmosphere (0315, 0325); 1615 Global Change: Biogeochemical processes (4805). Read Full Article (file size: 206703 bytes) Cited by Citation: Niyogi, D., et al. (2004), Direct observations of the effects of aerosol loading on net ecosystem CO₂ exchanges over different landscapes, Geophys. Res. Lett., 31, L20506, doi:10.1029/2004GL020915. Copyright 2004 by the American Geophysical Union.

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