HR: 0800h
AN: B51A-0929    [Abstracts]
TI: Examining Advection Effects on Eddy Flux Measurements at the Niwot Ridge AmeriFlux Site in the Colorado Rocky Mountains
AU: * Yi, C
EM: yic@colorado.edu
AF: University of Colorado, Department of Ecology, Evolutionary Biology, Campus Box 334, Boulder, CO 80309-0334 United States
AU: Anderson, D E
EM: deander@usgs.gov
AF: U.S. Geological Survey, Water Resources Division, Denver Federal Center, Lakewood, CO 80225 United States
AU: Burns, S P
EM: Sean.Burns@Colorado.EDU
AF: University of Colorado, Department of Ecology, Evolutionary Biology, Campus Box 334, Boulder, CO 80309-0334 United States
AU: Turnipseed, A A
EM: turnip@ucar.edu
AF: University of Colorado, Department of Ecology, Evolutionary Biology, Campus Box 334, Boulder, CO 80309-0334 United States
AU: Turnipseed, A A
EM: turnip@ucar.edu
AF: National Center for Atmospheric Research, Atmospheric Chemistry Division, Boulder, CO 80503 United States
AU: Monson, R K
EM: Russell.Monson@colorado.edu
AF: University of Colorado, Department of Ecology, Evolutionary Biology, Campus Box 334, Boulder, CO 80309-0334 United States
AB: Neglecting CO2 advection in eddy flux measurements is questionable and measuring horizontal CO2 advection from a single tower is difficult. We estimate the contributions of horizontal and vertical advection to the net ecosystem exchange (NEE) of CO2 by using a 3-dimentional measure system that consists of four eddy flux towers in a complex terrain in the Rocky Mountain of Colorado. The measurements showed that horizontal advection components were stronger in the stronger carbon source/sink levels (tree crown and near soil levels) than the other levels. The magnitudes of both horizontal and vertical advective fluxes are similar and opposite in sign, and increase with decreasing of friction velocity (u*). We also examined the validity of the spatial similarity assumption for the vertical CO2 profiles that is usually used in estimating horizontal advection fluxes. The measurements showed that the spatial similarity method resulted in 36% underestimate of the horizontal advection fluxes as u*$<$0.22 m/s , 79% overestimate as 0.22 m/s $<$u* $<$0.66 m/s, and no significant difference as u*$>$0.66 m/s.
DE: 3322 Land/atmosphere interactions
DE: 3307 Boundary layer processes
DE: 1600 GLOBAL CHANGE (New category)
DE: 1615 Biogeochemical processes (4805)
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting