HR: 13:40h
AN: B33G-01    [Abstracts]
TI: Trace Gas Transport Over Complex Terrain
AU: * Sun, J
EM: jsun@ucar.edu
AF: National Center for Atmospheric Research, 3450 Mitchell Lane, Boulder, CO 80301 United States
AU: Burns, S P
EM: sean@ucar.edu
AF: National Center for Atmospheric Research, 3450 Mitchell Lane, Boulder, CO 80301 United States
AU: Delany, A C
EM: acdelany@worldnet.att.net
AF: National Center for Atmospheric Research, 3450 Mitchell Lane, Boulder, CO 80301 United States
AU: Oncley, S P
EM: oncley@ucar.edu
AF: National Center for Atmospheric Research, 3450 Mitchell Lane, Boulder, CO 80301 United States
AU: Turnipseed, A A
EM: turnip@ucar.edu
AF: National Center for Atmospheric Research, 3450 Mitchell Lane, Boulder, CO 80301 United States
AU: Stephens, B B
EM: stephens@ucar.edu
AF: National Center for Atmospheric Research, 3450 Mitchell Lane, Boulder, CO 80301 United States
AU: Monson, R K
EM: monsonr@colorado.edu
AF: University of Colorado, Campus Box 334, Boulder, CO 80309 United States
AU: Anderson, D E
EM: deander@usgs.gov
AF: U.S. Geological Survey, M.S. 413, Federal Center, Denver, CO 80225-0046 United States
AB: Carbon dioxide transport at the Niwot Ridge AmeriFlux site was investigated in both gravity and streamline coordinates during a pilot experiment. We found that the nighttime drainage flow and the daytime upslope flow played important roles in the trace gas budget, such as CO₂ and water vapor, at this about 6% sloped forest site. Most of time, the canopy flow was decoupled from the air above; the air within the canopy was dominated by drainage and upslope flows while the air above was dominated by prevailing westerlies. At night the flow was stably stratified everywhere but less stable within than above the canopy; while during the day, the air was mostly stable within the canopy layer, especially near the bottom of the canopy, and the layer above was unstable. Protected by the overlying canopy, the drainage flow was responsible for transporting CO₂ at night while the stable layer above the canopy prevented upward CO₂ transport. In the early morning, the upslope flow transported the nighttime accumulation of moist and CO₂-enhanced air up the slope. The reduction of the CO₂ concentration in the early morning was associated with photosynthesis, upslope flow, and flux venting. The daytime stable boundary layer within the canopy prevented CO₂ venting and provided favorable conditions for CO₂ uptake, where the CO₂ concentration was relatively high from both local and remote respiration, and both direct and diffused solar radiation were available for photosynthesis. Therefore, both the CO₂ respiration at night and the CO₂ uptake during the day are underestimated if the horizontal transport of CO₂ is not monitored; and the two components may not cancel out.
DE: 1843 Land/atmosphere interactions (1218, 1631, 3322)
DE: 3307 Boundary layer processes
DE: 3379 Turbulence (4490)
DE: 4806 Carbon cycling (0428)
SC: Biogeosciences [B]
MN: Fall Meeting 2005