Persistent Link:
http://hdl.handle.net/10150/289209
Title:
Studies with the Biosphere-Atmosphere Transfer Scheme
Author:
Morrill, Jean Constance
Issue Date:
2000
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:
In order to better model the climate system, land-surface models are continuously being improved. Several studies using the Biosphere-Atmosphere Transfer Scheme (BATS) are presented. One study compares simulations with the new ten-layer soil model (TLSM) and the previous BATS soil model at global and regional scales. TLSM tends to have much higher bare soil evaporation than the previous soil model. Soil in regions with high precipitation became wetter, while soil in regions with less precipitation became much drier. Potential errors in TLSM included underpredicted runoff and high-latitude transpiration. Corrections for these errors were incorporated and tested at six points. Surface runoff is increased by extracting water from the upper three TLSM layers rather than only the top layer. Bare soil evaporation is limited to the water present in the surface soil layer. A diurnal temporal error in the downward longwave radiation forcing data did not appear to significantly affect simulated long-term or large-scale averages. However, the assumption of uniform hourly distribution of 6-hour total precipitation did impact the partitioning of precipitation into evaporation, transpiration and runoff. A new method for modeling vertical water flow in heterogeneous porous media using the water-content based form of Richards equation is described, then used with BATS/TLSM to simulate the boreal forest energy and water exchanges at a black spruce site, where a thick moss layer covers a peat/loam soil, and at an aspen site with a homogenous clay soil. The moss is treated as a type of porous media, so its unique hydraulic and thermal properties can be modeled directly. Simulated net radiation is very similar to that observed over the summer months at both sites, but latent heat is greatly overestimated and simulated sensible heat fluxes are not well correlated with the observations. Observed soil temperature profiles and soil water content profiles are well captured at the black spruce site, as is the ability of moss to keep the underlying soil layers moist and cool. Despite the successful modifications made to TLSM during this study, the overestimation of evaporation remains a problem that should be addressed before widespread use of this model occurs.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Hydrology.; Agriculture, Soil Science.; Physics, Atmospheric Science.; Environmental Sciences.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Hydrology and Water Resources
Degree Grantor:
University of Arizona
Advisor:
Dickinson, Robert E.; Shuttleworth, W. James

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleStudies with the Biosphere-Atmosphere Transfer Schemeen_US
dc.creatorMorrill, Jean Constanceen_US
dc.contributor.authorMorrill, Jean Constanceen_US
dc.date.issued2000en_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.abstractIn order to better model the climate system, land-surface models are continuously being improved. Several studies using the Biosphere-Atmosphere Transfer Scheme (BATS) are presented. One study compares simulations with the new ten-layer soil model (TLSM) and the previous BATS soil model at global and regional scales. TLSM tends to have much higher bare soil evaporation than the previous soil model. Soil in regions with high precipitation became wetter, while soil in regions with less precipitation became much drier. Potential errors in TLSM included underpredicted runoff and high-latitude transpiration. Corrections for these errors were incorporated and tested at six points. Surface runoff is increased by extracting water from the upper three TLSM layers rather than only the top layer. Bare soil evaporation is limited to the water present in the surface soil layer. A diurnal temporal error in the downward longwave radiation forcing data did not appear to significantly affect simulated long-term or large-scale averages. However, the assumption of uniform hourly distribution of 6-hour total precipitation did impact the partitioning of precipitation into evaporation, transpiration and runoff. A new method for modeling vertical water flow in heterogeneous porous media using the water-content based form of Richards equation is described, then used with BATS/TLSM to simulate the boreal forest energy and water exchanges at a black spruce site, where a thick moss layer covers a peat/loam soil, and at an aspen site with a homogenous clay soil. The moss is treated as a type of porous media, so its unique hydraulic and thermal properties can be modeled directly. Simulated net radiation is very similar to that observed over the summer months at both sites, but latent heat is greatly overestimated and simulated sensible heat fluxes are not well correlated with the observations. Observed soil temperature profiles and soil water content profiles are well captured at the black spruce site, as is the ability of moss to keep the underlying soil layers moist and cool. Despite the successful modifications made to TLSM during this study, the overestimation of evaporation remains a problem that should be addressed before widespread use of this model occurs.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectHydrology.en_US
dc.subjectAgriculture, Soil Science.en_US
dc.subjectPhysics, Atmospheric Science.en_US
dc.subjectEnvironmental Sciences.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineHydrology and Water Resourcesen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorDickinson, Robert E.en_US
dc.contributor.advisorShuttleworth, W. Jamesen_US
dc.identifier.proquest9992084en_US
dc.identifier.bibrecord.b41167284en_US
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