HR: 1330h
AN: H43B-11    [Abstracts]
TI: Impact of vegetation root distribution and soil moisture on evaporation simulations
AU: * Liu, H
EM: Heping.Liu@jsums.edu
AF: Jackson State University, Dept of Physics, Atmos. Sci. & General Sci. P.O. Box 17660, Jackson, MS 39217
AB: An accurate description of root distributions and soil moisture regimes has great impacts on evapotranspiration simulations, leading to difference in surface energy partitioning. We have designed three scenarios to test the effects of different parameterization schemes of root distributions on energy flux partitioning (i.e. change in Bowen ratio) using the off-line NCAR CLM2.0 land-surface model. We use the data measured in a coniferous forest in Alaska (63° 53' N 145° 44' W) in the 2002 summer (from June 20 to August 10, 2002). Compared with the fluxes measured over the black spruce forest, the uniform root distribution in our simulations leads to ~12% less latent heat fluxes and ~15% higher sensible heat fluxes. Because the soil moisture increases with depth in our site, the uniform root distribution may cause the reduced transpiration in the root layer. Also, the transpiration rates are limited in the upper layer by the lower soil moisture even though there is an increased root density. The exponential root distribution leads to ~16% higher latent heat fluxes and ~15% lower sensible heat fluxes. The higher latent heat flux may be due to the higher soil moisture content that is set below 40 cm depth with a higher root density in this model than the real root density for the black spruce. The triangular root distribution gives a reasonable result even though the latent heat flux is 6% higher than measurements and sensible heat flux is 8% lower than measurements. The difference could be due to the other factors that control energy partitioning or due to the discrepancy between the real root distribution and the triangular root distribution. It is expected that these results have large implications on boundary layer developments. For example, the uniform root distribution could lead to a drier and higher planetary boundary layer while the exponential root distribution could cause a moister and lower planetary boundary layer relative to the real one.
DE: 1878 Water/energy interactions
SC: Hydrology [H]
MN: 2005 Joint Assembly