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• 931. [Article] 3D Hydrodynamic Model Development and Verification

  A three-dimensional numerical model was developed to simulate hydrodynamic, temperature, and water quality distributions in rivers and lakes. In an attempt to get rid of the extra approximation and complexity, ...

  Citation × Citation Citation Abstract Copy Title: 3D Hydrodynamic Model Development and Verification Author: Al-Zubaidi, Hussein A. M. Year: 2016 A three-dimensional numerical model was developed to simulate hydrodynamic, temperature, and water quality distributions in rivers and lakes. In an attempt to get rid of the extra approximation and complexity, no coordinate transformation has been done and z-coordinate system has been employed. The governing equations are the continuity equation, free surface equation, momentum equations, and conservation equations of temperature and water quality. The model employs the time splitting technique which allows splitting the directions in which we end with two-dimensional governing equations and eventually the solution ends with a tri-diagonal matrix, which is easily solved by Thomas algorithm. The first step after developing a numerical model and before adding more features or applying the model to a real case, the model should be verified. The verification of the model was done by implementing the model to known solutions test cases in additional to evaluating whether the code preserves fluid mass. A series of test cases is performed by comparing the model results with the analytical solutions as proposed by many modelers. The model showed good agreement between the analytical and the numerical solution. Title: 3D Hydrodynamic Model Development and Verification Author: Al-Zubaidi, Hussein A. M. Year: 2016 A three-dimensional numerical model was developed to simulate hydrodynamic, temperature, and water quality distributions in rivers and lakes. In an attempt to get rid of the extra approximation and complexity, no coordinate transformation has been done and z-coordinate system has been employed. The governing equations are the continuity equation, free surface equation, momentum equations, and conservation equations of temperature and water quality. The model employs the time splitting technique which allows splitting the directions in which we end with two-dimensional governing equations and eventually the solution ends with a tri-diagonal matrix, which is easily solved by Thomas algorithm. The first step after developing a numerical model and before adding more features or applying the model to a real case, the model should be verified. The verification of the model was done by implementing the model to known solutions test cases in additional to evaluating whether the code preserves fluid mass. A series of test cases is performed by comparing the model results with the analytical solutions as proposed by many modelers. The model showed good agreement between the analytical and the numerical solution. Close

• 932. [Article] Water vapor transport in the vicinity of imbibing saline plumes: Homogeneous and layered unsaturated porous media

  This is the publisher’s final pdf. The published article is copyrighted by American Geophysical Union and can be found at: http://sites.agu.org/.

  Citation × Citation Citation Abstract Copy Title: Water vapor transport in the vicinity of imbibing saline plumes: Homogeneous and layered unsaturated porous media Author: Weisbrod, Noam, McGinnis, Thomas, Niemet, Michael R., Selker, John S. This is the publisher’s final pdf. The published article is copyrighted by American Geophysical Union and can be found at: http://sites.agu.org/. Title: Water vapor transport in the vicinity of imbibing saline plumes: Homogeneous and layered unsaturated porous media Author: Weisbrod, Noam, McGinnis, Thomas, Niemet, Michael R., Selker, John S. This is the publisher’s final pdf. The published article is copyrighted by American Geophysical Union and can be found at: http://sites.agu.org/. Close

• 933. [Article] The ventilated pool: a model of subtropical mode water

  An analytical model of subtropical mode water is presented, based on ventilated thermocline theory and on numerical solutions of a planetary geostrophic basin model. In ventilated thermocline theory, the ...

  Citation × Citation Citation Abstract Copy Title: The ventilated pool: a model of subtropical mode water Author: Vallis, G. K., Dewar, W. K., Samelson, Roger M. An analytical model of subtropical mode water is presented, based on ventilated thermocline theory and on numerical solutions of a planetary geostrophic basin model. In ventilated thermocline theory, the western pool is a region bounded on the east by subsurface streamlines that outcrop at the western edge of the interior, and in which additional dynamical assumptions are necessary to complete the solution. Solutions for the western pool were originally obtained under the assumption that the potential vorticity of the subsurface layer was homogenized. In the present theory, it is instead assumed that all of the water in the pool region is ventilated, and therefore that all the Sverdrup transport is carried in the uppermost, outcropping layer. The result is the formation of a deep, vertically homogeneous, fluid layer in the northwest corner of the subtropical gyre that extends from the surface to the base of the ventilated thermocline. This ventilated pool is an analog of the observed subtropical mode waters. The pool also has the interesting properties that it determines its own boundaries and affects the global potential vorticity-pressure relationship. When there are multiple outcropping layers, ventilated pool fluid is subducted to form a set of nested annuli in ventilated, subsurface layers, which are the deepest subducted layers in the ventilated thermocline. Title: The ventilated pool: a model of subtropical mode water Author: Vallis, G. K., Dewar, W. K., Samelson, Roger M. An analytical model of subtropical mode water is presented, based on ventilated thermocline theory and on numerical solutions of a planetary geostrophic basin model. In ventilated thermocline theory, the western pool is a region bounded on the east by subsurface streamlines that outcrop at the western edge of the interior, and in which additional dynamical assumptions are necessary to complete the solution. Solutions for the western pool were originally obtained under the assumption that the potential vorticity of the subsurface layer was homogenized. In the present theory, it is instead assumed that all of the water in the pool region is ventilated, and therefore that all the Sverdrup transport is carried in the uppermost, outcropping layer. The result is the formation of a deep, vertically homogeneous, fluid layer in the northwest corner of the subtropical gyre that extends from the surface to the base of the ventilated thermocline. This ventilated pool is an analog of the observed subtropical mode waters. The pool also has the interesting properties that it determines its own boundaries and affects the global potential vorticity-pressure relationship. When there are multiple outcropping layers, ventilated pool fluid is subducted to form a set of nested annuli in ventilated, subsurface layers, which are the deepest subducted layers in the ventilated thermocline. Close

• 934. [Image] Downhole Heat Exchanger for Shallow Geothermal Systems: Performance, Economics and Applicability

  	Heat exchangers located within the wellbore of shallow geothermal resources are presently being used at several locations in the U.S. These heat exchangers are referred to as downhole heat exchangers. ...
  	Citation × Citation Citation Abstract Copy Title: Downhole Heat Exchanger for Shallow Geothermal Systems: Performance, Economics and Applicability Author: Reistad, G. M. Heat exchangers located within the wellbore of shallow geothermal resources are presently being used at several locations in the U.S. These heat exchangers are referred to as downhole heat exchangers. Such installations can have thermal energy output capacities as high as 1 MW for space heating with source water temperature of 90 to 100°C. This work reports on the performance and economics of downhole heat exchangers relative to the alternative geothermal system which pumps the fluid out of the ground and uses heat exchangers located at the earth's surface. Results indicate that the downhole heat exchange systems for capacity requirements less than about 500 to 100 kW are in general more desirable than the surface heat exchange systems for low capacity (less than about 500 to 1000 kW) requirements and shallow geothermal resources. For higher capacities the surface heat exchange systems become more economical. Furthermore, for large depths, the high capacities available from the surface systems are required in order to make the geothermal energy competitive with other sources Title: Downhole Heat Exchanger for Shallow Geothermal Systems: Performance, Economics and Applicability Author: Reistad, G. M. Heat exchangers located within the wellbore of shallow geothermal resources are presently being used at several locations in the U.S. These heat exchangers are referred to as downhole heat exchangers. Such installations can have thermal energy output capacities as high as 1 MW for space heating with source water temperature of 90 to 100°C. This work reports on the performance and economics of downhole heat exchangers relative to the alternative geothermal system which pumps the fluid out of the ground and uses heat exchangers located at the earth's surface. Results indicate that the downhole heat exchange systems for capacity requirements less than about 500 to 100 kW are in general more desirable than the surface heat exchange systems for low capacity (less than about 500 to 1000 kW) requirements and shallow geothermal resources. For higher capacities the surface heat exchange systems become more economical. Furthermore, for large depths, the high capacities available from the surface systems are required in order to make the geothermal energy competitive with other sources Close

• 935. [Article] Engineering a Healthier Watershed: Middle School Students Use Engineering Design to Lessen the Impact of Their Campus' Impervious Surfaces on Their Local Watershed

  It is important that students understand not only how their local watershed functions, but also how it is being impacted by impervious surfaces. Additionally, students need experience exploring the scientific ...

  Citation × Citation Citation Abstract Copy Title: Engineering a Healthier Watershed: Middle School Students Use Engineering Design to Lessen the Impact of Their Campus' Impervious Surfaces on Their Local Watershed Author: Gardner, Elizabeth Claire Year: 2015 It is important that students understand not only how their local watershed functions, but also how it is being impacted by impervious surfaces. Additionally, students need experience exploring the scientific and engineering practices that are necessary for a strong STEM background. With this knowledge students can be empowered to tackle this real and local problem using engineering design, a powerful practice gaining momentum and clarity through its prominence in the recent Framework for K-12 Science Education. Twenty classes of suburban sixth-graders participated in a new five-week Watershed Engineering Design Unit taught by their regular science teachers. Students engaged in scientific inquiry to learn about the structure, function, and health of their local watersheds, focusing on the effects of impervious surfaces. In small groups, students used the engineering design process to propose solutions to lessen the impact of runoff from their school campuses. The goal of this evaluation was to determine the effectiveness of the curriculum in terms of student gains in understanding of (1) watershed function, (2) the impact of impervious surfaces, and (3) the engineering design process. To determine the impact of this curriculum on their learning, students took multiple-choice pre- and post-assessments made up of items covering the three categories above. This data was analyzed for statistical significance using a lower-tailed paired sample t-test. All three objectives showed statistically significant learning gains and the results were used to recommend improvements to the curriculum and the assessment instrument for future iterations. Title: Engineering a Healthier Watershed: Middle School Students Use Engineering Design to Lessen the Impact of Their Campus' Impervious Surfaces on Their Local Watershed Author: Gardner, Elizabeth Claire Year: 2015 It is important that students understand not only how their local watershed functions, but also how it is being impacted by impervious surfaces. Additionally, students need experience exploring the scientific and engineering practices that are necessary for a strong STEM background. With this knowledge students can be empowered to tackle this real and local problem using engineering design, a powerful practice gaining momentum and clarity through its prominence in the recent Framework for K-12 Science Education. Twenty classes of suburban sixth-graders participated in a new five-week Watershed Engineering Design Unit taught by their regular science teachers. Students engaged in scientific inquiry to learn about the structure, function, and health of their local watersheds, focusing on the effects of impervious surfaces. In small groups, students used the engineering design process to propose solutions to lessen the impact of runoff from their school campuses. The goal of this evaluation was to determine the effectiveness of the curriculum in terms of student gains in understanding of (1) watershed function, (2) the impact of impervious surfaces, and (3) the engineering design process. To determine the impact of this curriculum on their learning, students took multiple-choice pre- and post-assessments made up of items covering the three categories above. This data was analyzed for statistical significance using a lower-tailed paired sample t-test. All three objectives showed statistically significant learning gains and the results were used to recommend improvements to the curriculum and the assessment instrument for future iterations. Close

• 936. [Article] Hydrophobic Surfactant Proteins Strongly Induce Negative Curvature

  The hydrophobic surfactant proteins SP-B and SP-C greatly accelerate the adsorption of vesicles containing the surfactant lipids to form a film that lowers the surface tension of the air/water interface ...

  Citation × Citation Citation Abstract Copy Title: Hydrophobic Surfactant Proteins Strongly Induce Negative Curvature Author: Chavarha, Mariya, Loney, Ryan W., Rananavare, Shankar B., Hall, Stephen B. Year: 2015 The hydrophobic surfactant proteins SP-B and SP-C greatly accelerate the adsorption of vesicles containing the surfactant lipids to form a film that lowers the surface tension of the air/water interface in the lungs. Pulmonary surfactant enters the interface by a process analogous to the fusion of two vesicles. As with fusion, several factors affect adsorption according to how they alter the curvature of lipid leaflets, suggesting that adsorption proceeds via a rate-limiting structure with negative curvature, in which the hydrophilic face of the phospholipid leaflets is concave. In the studies reported here, we tested whether the surfactant proteins might promote adsorption by inducing lipids to adopt a more negative curvature, closer to the configuration of the hypothetical intermediate. Our experiments used x-ray diffraction to determine how the proteins in their physiological ratio affect the radius of cylindrical monolayers in the negatively curved, inverse hexagonal phase. With binary mixtures of dioleoylphosphatidylethanolamine (DOPE) and dioleoylphosphatidylcholine (DOPC), the proteins produced a dose-related effect on curvature that depended on the phospholipid composition. With DOPE alone, the proteins produced no change. With an increasing mol fraction of DOPC, the response to the proteins increased, reaching a maximum 50% reduction in cylindrical radius at 5% (w/w) protein. This change represented a doubling of curvature at the outer cylindrical surface. The change in spontaneous curvature, defined at approximately the level of the glycerol group, would be greater. Analysis of the results in terms of a Langmuir model for binding to a surface suggests that the effect of the lipids is consistent with a change in the maximum binding capacity. Our findings show that surfactant proteins can promote negative curvature, and support the possibility that they facilitate adsorption by that mechanism. Title: Hydrophobic Surfactant Proteins Strongly Induce Negative Curvature Author: Chavarha, Mariya, Loney, Ryan W., Rananavare, Shankar B., Hall, Stephen B. Year: 2015 The hydrophobic surfactant proteins SP-B and SP-C greatly accelerate the adsorption of vesicles containing the surfactant lipids to form a film that lowers the surface tension of the air/water interface in the lungs. Pulmonary surfactant enters the interface by a process analogous to the fusion of two vesicles. As with fusion, several factors affect adsorption according to how they alter the curvature of lipid leaflets, suggesting that adsorption proceeds via a rate-limiting structure with negative curvature, in which the hydrophilic face of the phospholipid leaflets is concave. In the studies reported here, we tested whether the surfactant proteins might promote adsorption by inducing lipids to adopt a more negative curvature, closer to the configuration of the hypothetical intermediate. Our experiments used x-ray diffraction to determine how the proteins in their physiological ratio affect the radius of cylindrical monolayers in the negatively curved, inverse hexagonal phase. With binary mixtures of dioleoylphosphatidylethanolamine (DOPE) and dioleoylphosphatidylcholine (DOPC), the proteins produced a dose-related effect on curvature that depended on the phospholipid composition. With DOPE alone, the proteins produced no change. With an increasing mol fraction of DOPC, the response to the proteins increased, reaching a maximum 50% reduction in cylindrical radius at 5% (w/w) protein. This change represented a doubling of curvature at the outer cylindrical surface. The change in spontaneous curvature, defined at approximately the level of the glycerol group, would be greater. Analysis of the results in terms of a Langmuir model for binding to a surface suggests that the effect of the lipids is consistent with a change in the maximum binding capacity. Our findings show that surfactant proteins can promote negative curvature, and support the possibility that they facilitate adsorption by that mechanism. Close

• 937. [Article] Glacier Change on the Three Sisters Volcanoes, Oregon: 1900-2010

  A glacier responds to changes in climate by subsequent retreat and advance as a result of changes in snow inputs and outputs. Understanding these changes is important because shrinking glaciers limit and ...

  Citation × Citation Citation Abstract Copy Title: Glacier Change on the Three Sisters Volcanoes, Oregon: 1900-2010 Author: Ohlschlager, Justin George Year: 2015 A glacier responds to changes in climate by subsequent retreat and advance as a result of changes in snow inputs and outputs. Understanding these changes is important because shrinking glaciers limit and diminish local water resources. They contribute to alpine runoff in the late-summer months by delaying the maximum runoff until late in the melt season. A comprehensive glacier and perennial snowfield inventory has not been completed for the Three Sisters in Central Oregon. Using aerial photography, Digital Elevation Models (DEMs), previous studies, and historical ground based photographs these glacier and perennial snowfields were defined and their surface area change was quantified along with surface area and volume change for the 15 named glaciers for multiple years. The glaciers and perennial snowfields totaled 9.03 ± 1.65 km2 in 1949 and decreased to 7.1 ± 1.16 km2 in 2003 giving a total loss of -1.914 ± 0.974 km2 ( 21%). The 15 named glaciers totaled 12.43 ± 0.417 km2 in ~1900 and decreased to 5.65 ± 0.135 km2 in 2003 giving a total loss of -6.70 ± 0.439 km2 (54%) with more loss occurring in the early part of the century. It's estimated that the 15 named glaciers lost roughly 61% of volume from 1900 to 2010. From 1957 to 2010 their surface's dropped in elevation on average by -8.9m, losing an estimated 71.96 x 106 ± 2.87 x 106 m3 (53%) in total volume, seen across accumulation and ablation zones, with more loss happening from 1957 to 1990. There was no relationship found between topography and area. A small correlation was found between slope and increased volume change. Debris cover on glacier surfaces has increased and showed a correlation between decreasing area loss (no correlation with volume changes). Title: Glacier Change on the Three Sisters Volcanoes, Oregon: 1900-2010 Author: Ohlschlager, Justin George Year: 2015 A glacier responds to changes in climate by subsequent retreat and advance as a result of changes in snow inputs and outputs. Understanding these changes is important because shrinking glaciers limit and diminish local water resources. They contribute to alpine runoff in the late-summer months by delaying the maximum runoff until late in the melt season. A comprehensive glacier and perennial snowfield inventory has not been completed for the Three Sisters in Central Oregon. Using aerial photography, Digital Elevation Models (DEMs), previous studies, and historical ground based photographs these glacier and perennial snowfields were defined and their surface area change was quantified along with surface area and volume change for the 15 named glaciers for multiple years. The glaciers and perennial snowfields totaled 9.03 ± 1.65 km2 in 1949 and decreased to 7.1 ± 1.16 km2 in 2003 giving a total loss of -1.914 ± 0.974 km2 ( 21%). The 15 named glaciers totaled 12.43 ± 0.417 km2 in ~1900 and decreased to 5.65 ± 0.135 km2 in 2003 giving a total loss of -6.70 ± 0.439 km2 (54%) with more loss occurring in the early part of the century. It's estimated that the 15 named glaciers lost roughly 61% of volume from 1900 to 2010. From 1957 to 2010 their surface's dropped in elevation on average by -8.9m, losing an estimated 71.96 x 106 ± 2.87 x 106 m3 (53%) in total volume, seen across accumulation and ablation zones, with more loss happening from 1957 to 1990. There was no relationship found between topography and area. A small correlation was found between slope and increased volume change. Debris cover on glacier surfaces has increased and showed a correlation between decreasing area loss (no correlation with volume changes). Close

• 938. [Article] Surface Energy Balance and Melt Thresholds over 11 years at Taylor Glacier, Antarctica

  In the McMurdo Dry Valleys, Victoria Land, Antarctica, melting of glacial ice is the primary source of water to streams, lakes, and associated ecosystems. To understand geochemical fluxes and ecological ...

  Citation × Citation Citation Abstract Copy Title: Surface Energy Balance and Melt Thresholds over 11 years at Taylor Glacier, Antarctica Author: Hoffman, Matthew James, Fountain, Andrew G., Liston, Glen E. Year: 2008 In the McMurdo Dry Valleys, Victoria Land, Antarctica, melting of glacial ice is the primary source of water to streams, lakes, and associated ecosystems. To understand geochemical fluxes and ecological responses to past and future climates requires a physically based energy balance model. We applied a one-dimensional model to one site on Taylor Glacier using 11 years of daily meteorological data and seasonal ablation measurements. Inclusion of transmission of solar radiation into the ice was necessary to accurately model summer ablation and ice temperatures. Results showed good correspondence between calculated and measured ablation and ice temperatures over the 11 years. Ablation (18 cm a??) was dominated by sublimation with very few occurrences of melt (42 days during 11 years). Results also indicated that above freezing air temperatures did not necessarily result in melt and, in turn, melt occurred during subfreezing air temperatures under some conditions. For air temperatures near freezing, low wind speed was critically important for melt initiation. According to the model, subsurface melt, away from rocks and sediment in the ice, occurred three times more frequently than surface melt; occurs no deeper than 50 cm below the glacier surface; and was small, never exceeding 8% by mass. The magnitude of subsurface melting and the energy balance indicate that Taylor Title: Surface Energy Balance and Melt Thresholds over 11 years at Taylor Glacier, Antarctica Author: Hoffman, Matthew James, Fountain, Andrew G., Liston, Glen E. Year: 2008 In the McMurdo Dry Valleys, Victoria Land, Antarctica, melting of glacial ice is the primary source of water to streams, lakes, and associated ecosystems. To understand geochemical fluxes and ecological responses to past and future climates requires a physically based energy balance model. We applied a one-dimensional model to one site on Taylor Glacier using 11 years of daily meteorological data and seasonal ablation measurements. Inclusion of transmission of solar radiation into the ice was necessary to accurately model summer ablation and ice temperatures. Results showed good correspondence between calculated and measured ablation and ice temperatures over the 11 years. Ablation (18 cm a??) was dominated by sublimation with very few occurrences of melt (42 days during 11 years). Results also indicated that above freezing air temperatures did not necessarily result in melt and, in turn, melt occurred during subfreezing air temperatures under some conditions. For air temperatures near freezing, low wind speed was critically important for melt initiation. According to the model, subsurface melt, away from rocks and sediment in the ice, occurred three times more frequently than surface melt; occurs no deeper than 50 cm below the glacier surface; and was small, never exceeding 8% by mass. The magnitude of subsurface melting and the energy balance indicate that Taylor Close

• 939. [Article] Hydrographic conditions off northern Chile during the 1996–1998 La Nina and El Nino events

  Copyright 2002 by the American Geophysical Union

  Citation × Citation Citation Abstract Copy Title: Hydrographic conditions off northern Chile during the 1996–1998 La Nina and El Nino events Author: Blanco, Jose Luis, Strub, P. Ted, Carr, Mary-Elena, Thomas, Andrew C. Copyright 2002 by the American Geophysical Union Title: Hydrographic conditions off northern Chile during the 1996–1998 La Nina and El Nino events Author: Blanco, Jose Luis, Strub, P. Ted, Carr, Mary-Elena, Thomas, Andrew C. Copyright 2002 by the American Geophysical Union Close

• 940. [Article] Evidence of nitric acid uptake in warm cirrus anvil clouds during the NASA TC4 campaign

  TC4 was sponsored by the NASA Headquarters Atmospheric Composition Focus Group which includes the Tropospheric Chemistry Program, Upper Atmospheric Research Program, and Radiation Science Program.

  Citation × Citation Citation Abstract Copy Title: Evidence of nitric acid uptake in warm cirrus anvil clouds during the NASA TC4 campaign Author: Bansemer, Aaron, Heymsfield, Andrew J., Twohy, Cynthia, Dibb, Jack E., Scheuer, Eric, Rogers, David C. TC4 was sponsored by the NASA Headquarters Atmospheric Composition Focus Group which includes the Tropospheric Chemistry Program, Upper Atmospheric Research Program, and Radiation Science Program. Title: Evidence of nitric acid uptake in warm cirrus anvil clouds during the NASA TC4 campaign Author: Bansemer, Aaron, Heymsfield, Andrew J., Twohy, Cynthia, Dibb, Jack E., Scheuer, Eric, Rogers, David C. TC4 was sponsored by the NASA Headquarters Atmospheric Composition Focus Group which includes the Tropospheric Chemistry Program, Upper Atmospheric Research Program, and Radiation Science Program. Close