CAREER: Effect of Land-Surface Heterogeneity on Regional-Scale Fluxes Using a New Generation Large-Eddy Simulation

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0094200Porte-AgelMeasurement and prediction (from hydrologic, weather and climate model) of regional-scale fluxes of heat and water vapor are subject to substantital errors associated with our limited ability to understand and account for the effect of land-surface variability. For example, numerical weather models use boundary conditions based on similarity theory, which assumes homogeneity of the land surface and ignores subgrid-scale variability. This study addresses these limitations by advancing our understanding of the complex two-way coupling between land-surface heterogeneity and atmospheric turbulence through a novel combination of wind tunnel experiments, remote-sensing field measurements, and three-dimensional transient numerical simulations (large-eddy simulations). The wind tunnel experiments study the physics governing the relationship between instantaneous surface characteristics (shear stress) and air flow properties (wind velocity) in order to develop physically more realistic boundary conditions. A new generation LES will be developed to incorporate the improved boundary conditions, as well as new subgrid-scale turbulence. Performance for boundary layers over heterogeneous surfaces will be evaluated using wind tunnel experiments and field measurements from remote sensing. The model is used to study how land-surface variability propagates upwards and affects the atmospheric boundary layer. These results are expected to substantially improve our ability to parameterize land-atmosphere exchange processes and, consequently, the accuracy of hydrologic, weather and climate models.The education innovations are to:(1) Develop a new education tool that exploits the potential of LES to provide 3-D transient information of the turbulent flow above the land surface.(2) Develop and solidify curriculum to incorporate the motivation and fundamental ideas behind our research as they achieve pedagogical maturity. (3) Mentor and engage Ph.D, M.S., and undergraduate students in interdisciplinary research based on the coupling and feedback between the state-of-the-art experimental, numerical, and theoretical approaches.(4) Outreach through workshops for high school teachers and students, with special emphasis on students from groups traditionally underrepresented in science and engineering.