HR: 1340h
AN: B33D-1056    [Abstracts]
TI: Effects of Spatial Heterogeneity in Rainfall and Vegetation on the Space-Time Scaling of Soil-Moisture and Evapotranspiration
AU: * Puma, M J
EM: mpuma@princeton.edu
AF: Princeton University Department of Civil and Environmental Engineering, Engineering Quad., Princeton, NJ 08544 United States
AU: Rodriguez-Iturbe, I
EM: irodrigu@princeton.edu
AF: Princeton University Department of Civil and Environmental Engineering, Engineering Quad., Princeton, NJ 08544 United States
AU: Celia, M A
EM: celia@princeton.edu
AF: Princeton University Department of Civil and Environmental Engineering, Engineering Quad., Princeton, NJ 08544 United States
AU: Nordbotten, J M
EM: jnordbot@princeton.edu
AF: Princeton University Department of Civil and Environmental Engineering, Engineering Quad., Princeton, NJ 08544 United States
AU: Guswa, A J
EM: aguswa@email.smith.edu
AF: Smith College Picker Engineering, 51 College Lane, Northampton, MA 01063 United States
AB: The effects of spatial heterogeneity in rainfall and vegetation on the space-time scaling behavior of hydrologic variables controlling the water balance are outstanding issues in land-surface modeling. An important aspect of these effects is the variability of specified hydrologic variables and their relationships with scales characteristic of land-surface heterogeneity and a model's resolution. In this work, we focus on the spatial and temporal scaling properties of soil moisture and evapotranspiration for various types of rainfall and vegetation heterogeneity in a Texas water-limited ecosystem. A detailed model simulates stochastic rainfall in space and time for multiple realizations to compute daily values of these variables over a range of spatial and temporal averaging windows. Results of our simulations indicate that the spatial variance of soil moisture and evapotranspiration decrease with increasing averaging area such that spatial threshold scales, or representative averaging areas, can be identified. Spatial threshold scales have been used in the literature to infer the importance of modeling land-surface heterogeneity explicitly. The results are generalized by relating the spatial threshold scales to a dimensionless group of parameters that includes length scales characteristic of the heterogeneity and the model's resolution. In the time domain, we compute the temporal variance over multiple realizations for different temporal averaging windows. This computation enables prediction of a temporal threshold scale, which indicates the amount of time necessary to predict accurately the mean of the variables. The space-time scaling behavior is then explored and results demonstrate that the spatial and temporal threshold scales are interdependent. These space-time results provide valuable insight into sampling and resolution issues for field and modeling studies of soil moisture and evapotranspiration.
DE: 1813 Eco-hydrology
DE: 1818 Evapotranspiration
DE: 1839 Hydrologic scaling
DE: 1847 Modeling
DE: 1866 Soil moisture
SC: Biogeosciences [B]
MN: Fall Meeting 2005