HR: 14:50h
AN: B43C-05    [Abstracts]
TI: Flux Footprint Simulation in Complex Terrain
AU: * Klaassen, W
EM: W.Klaassen@biol.rug.nl
AF: Wim Klaassen, Marine Biology University of Groningen Post Box 14, Haren, 9750 AA Netherlands
AU: Sogachev, A
EM: Andrei.Sogachev@helsinki.fi
AF: Andrey Sogachev, Atmospheric Sciences University of Helsinki Post Box 68, Helsinki, FIN-00014 Finland
AB: Atmospheric measurements of forest exchange processes are often executed under non-ideal conditions. Observations show that energy fluxes over forest may even exceed the surface fluxes originating from the forest and the upwind terrain. The overshoot of atmospheric fluxes is caused by atmospheric flow obstruction at the forest edge. In order to calculate the forest surface flux from the atmospheric measurements, an estimate should be made of the corrections for upwind fluxes as well as for flux deformation by inhomogeneous turbulence. A new footprint model is presented with explicit calculation of the atmospheric turbulence field. The model is capable to simulate observed overshoot and undershoot of atmospheric fluxes downwind of a forest edge. Model results are sensitive to forest structural parameters. Values are given which part of the atmospheric flux originates from the forest and which part from the upwind terrain. It is shown that in conditions of inhomogeneous turbulence, the sum of these parts may deviate significantly from unity. It is concluded that perturbations of the atmospheric flow affect flux measurements in complex terrain. It is recommended to use a footprint model which accounts for the actual turbulence pattern in order to analyze atmospheric flux measurements in complex terrain.
DE: 3322 Land/atmosphere interactions
DE: 3379 Turbulence
DE: 0315 Biosphere/atmosphere interactions
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting