Extended Abstract (36K)9.8
Mixing in open canopies
Young-Hee Lee, Kyungpook National University, Daegu, South Korea; and L. Mahrt
In open canopies, the subcanopy flux can account for a significant fraction of the total heat, moisture and carbon dioxide fluxes from the forest and therefore, the turbulent exchange coefficient within canopies becomes important. A first-order closure model is developed within and above the vegetation canopy for heat flux based on analysis of data from the old aspen site in BOREAS and a ponderosa pine site in central Oregon. A new formulation for subcanopy fluxes is developed in terms of a mixing length that depends on local stability. In the trunk space, the flux-gradient relationship for heat approximately follows Monin-Obukhov similarity theory for near neutral and unstable conditions in spite of the fact that the conditions for Monin-Obukhov similarity theory are not satisfied. At the pine site, a strong nocturnal inversion often develops in the canopy overstory, which prevents significant exchange of heat and CO2 between the soil surface and the air above the canopy. This strong inversion is examined in terms of cold air drainage in the subcanopy trunk space.
Session 9, Surface layer interactions, fluxes, and heterogeneity (Parallel with Session 10)
Thursday, 12 August 2004, 1:30 PM-5:45 PM, Vermont Room
Previous paper Next paper
Recorded presentation