P1.7
Atmospheric tracer measurements and Lagrangian modeling of CO2 advective fluxes in nighttime drainage flows
Tara Strand, Washington State University, Pullman, WA; and B. Lamb, G. Allwine, A. Turnipseed, and R. Monson
At the Niwot Ridge Ameriflux site, located in Roosevelt National Forest in the Rocky Mountains of Colorado, rapid radiative cooling, sudden elevation changes in plant community and sloped terrain contribute to the development of nighttime, downslope, gravitational flows that cause horizontal advective fluxes of respired CO2. Sulfur hexafluoride (SF6) tracer studies were conducted to investigate scalar transport and dispersion at night and to provide the necessary data for evaluation and application of a Lagrangian puff forest canopy dispersion model. These studies provide information on the importance of scalar advection at sites with complex terrain with respect to the measured net ecosystem CO2 exchange (NEE). SF6 tracer releases were made from a single ground level point source during a 2001 field campaign and from a 200 m line source during the 2002 field campaign. Tracer concentrations were measured from a vertical profiling system using a continuous tracer analyser in all cases. The vertical concentration profiles showed that during nighttime drainage conditions, the tracer plume exhibited vertical diffusion limited to less than the canopy height at downwind distance of 200 m.
Poster Session 1, Posters for the 26th Conference on Agricultural and Forest Meteorology
Wednesday, 25 August 2004, 5:30 PM-8:30 PM
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