HR: 16:35h
AN: A54B-02    [Abstracts]
TI: Mechanistic Response of Terrestrial Plant Productivity and Surface Energy Budget to Routine Aerosol Loading over the Eastern U.S.
AU: * Matsui, T T
EM: matsui@agnes.gsfc.nasa.gov
AF: Goddard Earth Sciences and Technology Center, Goddard Earth Sciences and Technology Center, University of Maryland Baltimore County, Baltimore, MD, Baltimore, MD 20771, United States
AU: Beltran-Przekurat, A
EM: adriana@cires.colorado.edu
AF: Department of Atmospheric and Oceanic Sciences Cooperative Institute for Research in Environmental Sciences, Department of Atmospheric and Oceanic Sciences Cooperative Institute for Research in Environmental Sciences University of Colorado, Boulder, CO, Boulder, CO 80309, United States
AU: Niyogi, D
EM: dniyogi@purdue.edu
AF: Department of Agronomy, Department of Earth and Atmospheric Sciences, Purdue University, Department of Agronomy, Department of Earth and Atmospheric Sciences, Purdue University, IN, IN , United States
AU: Pielke, R A
EM: pielkesr@cires.colorado.edu
AF: Department of Atmospheric and Oceanic Sciences Cooperative Institute for Research in Environmental Sciences, Department of Atmospheric and Oceanic Sciences Cooperative Institute for Research in Environmental Sciences University of Colorado, Boulder, CO, Boulder, CO 80309, United States
AB: The aerosol direct effect not only reduces global irradiance but also increases diffuse radiation. Diffuse radiation is more homogeneously absorbed by the plant canopy and more efficiently utilized for the plant photosynthesis process than direct radiation. Thus, aerosol loading is expected to increase plant productivity (the aerosol diffuse- radiation effect). The study presents the spatio-temoporal variability of the aerosol diffuse-radiation effect over the eastern U.S., using a sun-shade canopy model. First, satellite and model aerosol optical depth (AOD) products are assimilated via an optimal interpolation technique, and a comparison against the ground-based observations shows that the satellite-model assimilated AOD product is superior to either a satellite or model product. Second, surface albedo, surface radiative temperature, CO2 flux, and sensible/latent heat fluxes in a sun-shade canopy model (Unified Land Model: ULM) are compared with corresponding satellite and ground-based observations. Tuning parameters in ULM are constrained by reducing model-observation discrepancies via the Gauss-Maquardt-Levemberg automatic optimization algorithm. Third, the well-calibrated ULM is run in an off-line mode for the warm seasons in 2000 and 2001. Downwelling shortwave radiation is computed with (a control experiment) and without (a potential experiment) assimilated daily AOD in all-sky conditions. The sensitivity experiments (control-potential) show that aerosol loading increases plant productivity in mixed forests and deciduous broadleaf forests in the southeastern U.S., while plant productivity is decreased over the croplands and grasslands. The spatio-temporal variability of aerosol diffuse-radiation effect is well explained by the variability of leaf area index (LAI), cloud optical depth, near-surface atmospheric temperature, and diurnal cycles. Due to the combination of the positive and negative effects, the aerosol diffuse-radiation effect changes plant productivity by only +0.5% in 2001 and -0.09% in 2000 from the potential experiment over the eastern U.S. It should be noted that this is the first regional scale analysis of this process, and the magnitude of sensitivity could vary for a coupled land-atmosphere experiment.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0428 Carbon cycling (4806)
DE: 1843 Land/atmosphere interactions (1218, 1631, 3322)
DE: 1846 Model calibration (3333)
DE: 1852 Plant uptake
SC: Atmospheric Sciences [A]
MN: 2007 Joint Assembly