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Utah State University (1997)

Surface heat flux estimation for arid regions using remotely sensed data

Abdalla, Seifeldin Hamad

Titre : Surface heat flux estimation for arid regions using remotely sensed data

Auteur : Abdalla, Seifeldin Hamad

Université de soutenance : Utah State University

Grade : Doctor of Philosophy (PhD) 1997

Résumé
Reliable estimates of surface heat fluxes in sparsely vegetated arid ecosystems are needed to improve the partitioning of available energy in hydrologic and mesoscale models. In this study, surface-dependent fluxes were estimated using input parameters derived from high-resolution airborne remotely sensed imagery. A multilayer model that separated the contributions of soils and plants to the energy balance components was developed in the study. The model is based on input parameters from both meteorological and remotely sensed data. The field data were collected in Goshute Valley, Nevada, during the summer of 1994. The estimated fluxes were verified using eddy correlation and Bowen ratio data. To minimize the complexity of the model, a grid size based on random existence of each class was chosen. The final product of the study was information layers representing the spatial variation of surface energy balance components for the different ecosystems of the Goshute desert valley. The estimated energy fluxes were well correlated with the measured fluxes, with root mean square less than 10 Watts/msp2. To produce such layers, some intermediate steps were followed : (1) Develop the P/T (partial/total) ratio for the TM band radiometer for plants and soils in a sparsely vegetated arid environment. (2) Estimate albedo values for the different types of soils and plants in the different sites, using the developed P/T ratio. (3) Digitize, correct, process, and classify the high resolution airborne thermal and multispectral video imagery to estimate surface temperature and extract the different proportions of soil and vegetation classes. (4) Integrate layers of albedo, emissivity, and temperature to produce a layer of net radiation. (5) Evaluate the spatial distribution of the surface roughness and aerodynamic resistance for each site. (6) Separate contributions of soils and plants to total sensible heat flux using a multilayer model approach that was based on the individual contributions of each class. (7) Develop spectral methods that depend on vegetation indices to quantify the temporal and spatial variation of the soil heat flux based on the spatial distribution of net radiation. The good agreement between the observed and estimated surface energy fluxes suggests that layers of surface energy fluxes for sparsely vegetated arid regions can be produced using airborne multispectral imagery and used for input and verification of mesoscale atmospheric and energy balance models.

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