Surface flux measurement and modeling at a semi-arid Sonoran Desert site

Persistent Link:
http://hdl.handle.net/10150/191383
Title:
Surface flux measurement and modeling at a semi-arid Sonoran Desert site
Author:
Unland, Helene Emmi Karin
Issue Date:
1996
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Continuous measurements of near-surface weather variables using an automatic weather station and intermittent measurements of surface energy, momentum and carbon dioxide fluxes using Bowen ratio, eddy covariance, and sigma-T systems were collected for 13 months at a semi-arid Sonoran Desert site near Tucson, Arizona. Comparisons between measured fluxes made simultaneously with different instrumental systems show acceptable agreement. To investigate the influence of Crassulacean Acid Metabolism plants on carbon dioxide flux, measurements were sustained through the night. Observations were analyzed to characterize the typical magnitude of diurnal and seasonal variations in surface energy and carbon dioxide exchanges for this vegetation type and were then used to validate and calibrate the surface energy balance simulated by the Biosphere-Atmosphere Transfer Scheme. Using the standard "semi-desert" soil and vegetation parameters specified in the National Center for Atmospheric Research Community Climate Model version 2 gave a poor description of surface energy exchange. However, a combination of site-specific soil and vegetation parameters, and a simple optimization to modify the value of minimum surface resistance and plant wilting parameters, substantially improved the model performance. The site-specific parameters reflect the fact that the vegetation fraction is greater than assumed in the standard parameter set, leaf area index and minimum stomatal resistance are less, soils at the study site contain more clay, but the plants' wilting point is lower than this clay fraction would imply. These modified parameters more accurately describe the conservative character of the semidesert vegetation and the moderate nature of its response to the seasonal water cycle.
Type:
Thesis-Reproduction (electronic); text
LCSH Subjects:
Hydrology.; Climatic changes -- Measurement.; Climatic changes -- Mathematical models.
Degree Name:
M.S.
Degree Level:
masters
Degree Program:
Hydrology and Water Resources; Graduate College
Degree Grantor:
University of Arizona
Committee Chair:
Shuttleworth, W. James

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleSurface flux measurement and modeling at a semi-arid Sonoran Desert siteen_US
dc.creatorUnland, Helene Emmi Karinen_US
dc.contributor.authorUnland, Helene Emmi Karinen_US
dc.date.issued1996en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractContinuous measurements of near-surface weather variables using an automatic weather station and intermittent measurements of surface energy, momentum and carbon dioxide fluxes using Bowen ratio, eddy covariance, and sigma-T systems were collected for 13 months at a semi-arid Sonoran Desert site near Tucson, Arizona. Comparisons between measured fluxes made simultaneously with different instrumental systems show acceptable agreement. To investigate the influence of Crassulacean Acid Metabolism plants on carbon dioxide flux, measurements were sustained through the night. Observations were analyzed to characterize the typical magnitude of diurnal and seasonal variations in surface energy and carbon dioxide exchanges for this vegetation type and were then used to validate and calibrate the surface energy balance simulated by the Biosphere-Atmosphere Transfer Scheme. Using the standard "semi-desert" soil and vegetation parameters specified in the National Center for Atmospheric Research Community Climate Model version 2 gave a poor description of surface energy exchange. However, a combination of site-specific soil and vegetation parameters, and a simple optimization to modify the value of minimum surface resistance and plant wilting parameters, substantially improved the model performance. The site-specific parameters reflect the fact that the vegetation fraction is greater than assumed in the standard parameter set, leaf area index and minimum stomatal resistance are less, soils at the study site contain more clay, but the plants' wilting point is lower than this clay fraction would imply. These modified parameters more accurately describe the conservative character of the semidesert vegetation and the moderate nature of its response to the seasonal water cycle.en_US
dc.description.notehydrology collectionen_US
dc.typeThesis-Reproduction (electronic)en_US
dc.typetexten_US
dc.subject.lcshHydrology.en_US
dc.subject.lcshClimatic changes -- Measurement.en_US
dc.subject.lcshClimatic changes -- Mathematical models.en_US
thesis.degree.nameM.S.en_US
thesis.degree.levelmastersen_US
thesis.degree.disciplineHydrology and Water Resourcesen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.chairShuttleworth, W. Jamesen_US
dc.identifier.oclc228306258en_US
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