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Accueil du site → Master → Etats Unis → 2020 → Evaluating the Effects of Vegetation Cover and Phenology on the Components of the Surface Energy Fluxes, Soil Temperature and its Damping Depth, Soil Moisture and the Partitioning of the Evapotranspiration Across Forest, Grassland and Desert Ecosystems

University of Oklahoma (2020)

Evaluating the Effects of Vegetation Cover and Phenology on the Components of the Surface Energy Fluxes, Soil Temperature and its Damping Depth, Soil Moisture and the Partitioning of the Evapotranspiration Across Forest, Grassland and Desert Ecosystems

Pham, Tri

Titre : Evaluating the Effects of Vegetation Cover and Phenology on the Components of the Surface Energy Fluxes, Soil Temperature and its Damping Depth, Soil Moisture and the Partitioning of the Evapotranspiration Across Forest, Grassland and Desert Ecosystems

Auteur : Pham, Tri

Université de soutenance : University of Oklahoma

Grade : MASTER OF SCIENCE (MS) 2020

Résumé partiel
The understanding and modeling of the effects of land-cover change on the behaviors of evapotranspiration flux and its partitioning, soil moisture, soil temperature, and surface energy fluxes which include ground heat flux, sensible heat flux, and latent heat flux (evapotranspiration) is an active research field with applications to hydrologic engineering. Knowledge of these shifts could improve our estimations of precipitation, heat waves, drought mechanisms, soil moisture and flood forecasting. This study utilized long-term eddy covariance measurements and remote sensing data to investigate the effects of both vegetation cover disturbance and vegetation phenology on key hydrologic variables at seven research sites in Oklahoma and Arizona. The study focused on : (1) the use of eddy covariance measurements and remote sensing data for comparison of surface energy fluxes, soil moisture, and soil temperatures, (2) the calibration and validation of the TIN-based Real-time Integrated Basin Simulator (tRIBS) hydrological model to simulate surface energy and water balance variables and to assess its ability to predict short- and long-term time series at hourly time steps, (3) the partitioning of the evapotranspiration into three components : transpiration from vegetation, wet canopy evaporation from intercepted precipitation on leaves and soil evaporation and the identification of the roles of vegetation and precipitation on the partitioning, (4) the calculation of the daily temperature damping depths at the research sites quantification of roles of vegetation and soil moisture and, (5) the development of a toolkit to automate and visualize tRIBS simulations and reduce human errors. This study found that : (1) tRIBS demonstrated its capability to conduct footprint type of simulations at an hourly time step by using process-based conceptualizations and remote sensing with high correlation and Nash-Sutcliffe model efficiency coefficients between simulations and observations. The model also captured the diurnal variability of the simulated variables, which potentially can be used to fill the gap in the missing eddy covariance measurements. (2) Across simulations sites, responses of simulated ground heat flux, sensible heat flux, and soil temperatures depended on soil heat conductivity and heat capacity parameters. Additionally, latent heat flux seemed to depend on both soil thermal properties but also on the stress thresholds for transpiration and evaporation, in addition to the hydraulic conductivity, air entry bubbling pressure, and pore distribution index. Soil moisture was more complex and sensitive to the saturated hydraulic conductivity and stress threshold. (3) In arid environments (i.e. Santa Rita, AZ), differences in vegetation cover represented differences in the distribution of the surface energy balance components.

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