ALBERT

Description: Hyporheic flow in streams has typically been studied separately from geomorphic processes. We investigated interactions between bed mobility and dynamic hyporheic storage of solutes and fine particles in a sand-bed stream before, during, and after a flood. A conservatively transported solute tracer (bromide) and a fine particles tracer (5 μm latex particles), a surrogate for fine particulate organic matter, were co-injected during base flow. The tracers were differentially stored, with fine particles penetrating more shallowly in hyporheic flow and retained more efficiently due to the high rate of particle filtration in bed sediment compared to solute. Tracer injections lasted 3.5 h after which we released a small flood from an upstream dam one hour later. Due to shallower storage in the bed, fine particles were rapidly entrained during the rising limb of the flood hydrograph. Rather than being flushed by the flood, we observed that solutes were stored longer due to expansion of hyporheic flow paths beneath the temporarily enlarged bedforms. Three important timescales determined the fate of solutes and fine particles: (1) flood duration, (2) relaxation time of flood-enlarged bedforms back to base flow dimensions, and (3) resulting adjustments and lag times of hyporheic flow. Recurrent transitions between these timescales explain why we observed a peak accumulation of natural particulate organic matter between 2 and 4 cm deep in the bed, i.e., below the scour layer of mobile bedforms but above the maximum depth of particle filtration in hyporheic flow paths. Thus, physical interactions between bed mobility and hyporheic transport influence how organic matter is stored in the bed and how long it is retained, which affects decomposition rate and metabolism of this southeastern Coastal Plain stream. In summary we found that dynamic interactions between hyporheic flow, bed mobility, and flow variation had strong but differential influences on base flow retention and flood mobilization of solutes and fine particulates. These hydrogeomorphic relationships have implications for microbial respiration of organic matter, carbon and nutrient cycling, and fate of contaminants in streams.

Description: [1]  Hyporheic flow in streams has typically been studied separately from geomorphic processes. We investigated interactions between bed mobility and dynamic hyporheic storage of solutes and fine particles in a sand-bed stream before, during, and after a flood. A conservatively transported solute tracer (bromide) and a fine particles tracer (5  μ m latex particles), a surrogate for fine particulate organic matter, were co-injected during base flow. The tracers were differentially stored, with fine particles penetrating more shallowly in hyporheic flow and retained more efficiently due to the high rate of particle filtration in bed sediment compared to solute. Tracer injections lasted 3.5 h after which we released a small flood from an upstream dam one hour later. Due to shallower storage in the bed, fine particles were rapidly entrained during the rising limb of the flood hydrograph. Rather than being flushed by the flood, we observed that solutes were stored longer due to expansion of hyporheic flow paths beneath the temporarily enlarged bedforms. Three important timescales determined the fate of solutes and fine particles: (1) flood duration, (2) relaxation time of flood-enlarged bedforms back to base flow dimensions, and (3) resulting adjustments and lag times of hyporheic flow. Recurrent transitions between these timescales explain why we observed a peak accumulation of natural particulate organic matter between 2 and 4 cm deep in the bed, i.e., below the scour layer of mobile bedforms but above the maximum depth of particle filtration in hyporheic flow paths. Thus, physical interactions between bed mobility and hyporheic transport influence how organic matter is stored in the bed and how long it is retained, which affects decomposition rate and metabolism of this southeastern Coastal Plain stream. In summary we found that dynamic interactions between hyporheic flow, bed mobility, and flow variation had strong but differential influences on base flow retention and flood mobilization of solutes and fine particulates. These hydrogeomorphic relationships have implications for microbial respiration of organic matter, carbon and nutrient cycling, and fate of contaminants in streams.

Description: ABSTRACT Fifty years of hyporheic zone research have shown the important role played by the hyporheic zone as an interface between groundwater and surface waters. However, it is only in the last two decades that what began as an empirical science has become a mechanistic science devoted to modeling studies of the complex fluid dynamical and biogeochemical mechanisms occurring in the hyporheic zone. These efforts have led to the picture of surface-subsurface water interactions as regulators of the form and function of fluvial ecosystems. Rather than being isolated systems, surface water bodies continuously interact with the subsurface. Exploration of hyporheic zone processes has led to a new appreciation of their wide reaching consequences for water quality and stream ecology. Modern research aims toward a unified approach, in which processes occurring in the hyporheic zone are key elements for the appreciation, management, and restoration of the whole river environment. In this unifying context, this review summarizes results from modeling studies and field observations about flow and transport processes in the hyporheic zone and describes the theories proposed in hydrology and fluid dynamics developed to quantitatively model and predict the hyporheic transport of water, heat, and dissolved and suspended compounds from sediment grain scale up to the watershed scale. The implications of these processes for stream biogeochemistry and ecology are also discussed.

Description: Data from the Global Oscillation Network Group (GONG) project and other helioseismic experiments provide a test for models of stellar interiors and for the thermodynamic and radiative properties, on which the models depend, of matter under the extreme conditions found in the sun. Current models are in agreement with the helioseismic inferences, which suggests, for example, that the disagreement between the predicted and observed fluxes of neutrinos from the sun is not caused by errors in the models. However, the GONG data reveal subtle errors in the models, such as an excess in sound speed just beneath the convection zone. These discrepancies indicate effects that have so far not been correctly accounted for; for example, it is plausible that the sound-speed differences reflect weak mixing in stellar interiors, of potential importance to the overall evolution of stars and ultimately to estimates of the age of the galaxy based on stellar evolution calculations.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Christensen-Dalsgaard -- Dappen -- Ajukov -- Anderson -- Antia -- Basu -- Baturin -- Berthomieu -- Chaboyer -- Chitre -- Cox -- Demarque -- Donatowicz -- Dziembowski -- Gabriel -- Gough -- Guenther -- Guzik -- Harvey -- Hill -- Houdek -- Iglesias -- Kosovichev -- Leibacher -- Morel -- Proffitt -- Provost -- Reiter -- Rhodes Jr -- Rogers -- Roxburgh -- Thompson -- Ulrich -- New York, N.Y. -- Science. 1996 May 31;272(5266):1286-92.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉J. Christensen-Dalsgaard and S. Basu are with Theoretical Astrophysics Center and Institute of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark. W. Dappen and E. J. Rhodes Jr. are with the Department of Physics and Astronomy, University of Southern California, Los Angeles, CA 90089, USA. S. V. Ajukov is with the Sternberg Astronomical Institute, Moscow, Russia. E. R. Anderson, J. W. Harvey, F. Hill, and J. W. Leibacher are with the National Solar Observatory, National Optical Astronomy Observatories, Tucson, AZ 85726, USA. H. M. Antia and S. M. Chitre are with the Tata Institute of Fundamental Research, Bombay, India. V. A. Baturin, I. W. Roxburgh, and M. J. Thompson are with the Astronomy Unit, Queen Mary and Westfield College, London E1 4NS, UK. G. Berthomieu, P. Morel, and J. Provost are with the Observatoire de la Cote d'Azur, Nice, France. B. Chaboyer is with CITA, University of Toronto, Toronto, Canada. A. N. Cox and J. A. Guzik are with Los Alamos National Laboratory, Los Alamos, NM 87545, USA. P. Demarque is with the Department of Astronomy, Yale University, New Haven, CT 06520, USA. J. Donatowicz and G. Houdek are with the Institut fur Astronomie, Universitat Wien, Vienna, Austria. W. A. Dziembowski is with the Copernicus Center, Warsaw, Poland. M. Gabriel is with the Institut d'Astrophysique, Universite de Liege, Liege, Belgium. D. O. Gough is with the Institute of Astronomy, University of Cambridge, Cambridge, UK. D. B. Guenther is with the Department of Astronomy and Physics, Saint Mary's University, Halifax, Nova Scotia, Canada. C. A. Iglesias and F. J. Rogers are with the Lawrence Livermore National Laboratory, Livermore, CA 94550, USA. A. G. Kosovichev is with Center for Space Science and Astrophysics, Stanford University, Stanford, CA 94305, USA. C. R. Proffitt is with Computer Sciences Corporation, Goddard Space Flight Center, Greenbelt, MD 20771, USA. J. Reiter is with the Mathematisches Institut, Technische Universitat Munchen, Munich, Germany. R. K. Ulrich is with the Department of Physics and Astronomy, University of California, Los Angeles, CA 90095, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8662456" target="_blank"〉PubMed〈/a〉

Description: Helioseismology requires nearly continuous observations of the oscillations of the solar surface for long periods of time in order to obtain precise measurements of the sun's normal modes of oscillation. The GONG project acquires velocity images from a network of six identical instruments distributed around the world. The GONG network began full operation in October 1995. It has achieved a duty cycle of 89 percent and reduced the magnitude of spectral artifacts by a factor of 280 in power, compared with single-site observations. The instrumental noise is less than the observed solar background.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Harvey -- Hill -- Hubbard -- Kennedy -- Leibacher -- Pintar -- Gilman -- Noyes -- Title -- Toomre -- Ulrich -- Bhatnagar -- Kennewell -- Marquette -- Patron -- Saa -- Yasukawa -- New York, N.Y. -- Science. 1996 May 31;272(5266):1284-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉J. W. Harvey, F. Hill, R. P. Hubbard, J. R. Kennedy, J. W. Leibacher, and J. A. Pintar are with the National Solar Observatory, National Optical Astronomy Observatories, Post Office Box 26732, Tucson, AZ 85726-6732, USA. P. A. Gilman is with the High Altitude Observatory, National Center for Atmospheric Research, Post Office Box 3000, Boulder, CO 80307, USA. R. W. Noyes is with the Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138, USA. A. M. Title is with the Lockheed Solar and Astrophysics Laboratory, Palo Alto, CA 94304, USA. J. Toomre is with JILA, University of Colorado, Boulder, CO 80309, USA. R. K. Ulrich is with the Department of Physics and Astronomy, University of California, Los Angeles, CA 90024, USA. A. Bhatnagar is with the Udaipur Solar Observatory, Physical Research Laboratory, Udaipur, India. J. A. Kennewell is with the Learmonth Solar Observatory, IPS Radio and Space Services, Exmouth, Western Australia, Australia. W. Marquette is with the Big Bear Solar Observatory, Big Bear City, CA 92314, and California Institute of Technology, 264-33, Pasadena, CA 91125, USA. J. Patron is with the Observatorio del Teide, Instituto Astrofisica de Canarias, La Laguna, Tenerife, Spain. O. Saa is with the Cerro Tololo Interamerican Observatory, National Optical Astronomy Observatories, La Serena, Chile. E. Yasukawa is with the Mauna Loa Solar Observatory, Hilo, HI 96720, and High Altitude Observatory, National Center for Atmospheric Research, Post Office Box 3000, Boulder, CO 80307, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8662455" target="_blank"〉PubMed〈/a〉

Description: Doppler velocity observations obtained by the Global Oscillation Network Group (GONG) instruments directly measure the nearly steady flows in the solar photosphere. The sun's differential rotation is accurately determined from single observations. The rotation profile with respect to latitude agrees well with previous measures, but it also shows a slight north-south asymmetry. Rotation profiles averaged over 27-day rotations of the sun reveal the torsional oscillation signal-weak, jetlike features, with amplitudes of 5 meters per second, that are associated with the sunspot latitude activity belts. A meridional circulation with a poleward flow of about 20 meters per second is also evident. Several characteristics of the surface flows suggest the presence of large convection cells.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hathaway -- Gilman -- Harvey -- Hill -- Howard -- Jones -- Kasher -- Leibacher -- Pintar -- Simon -- New York, N.Y. -- Science. 1996 May 31;272(5266):1306-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉D. H. Hathaway is in the Solar Physics Branch, Mail Code ES82, Space Sciences Laboratory, NASA/Marshall Space Flight Center, Huntsville, AL 35812, USA. P. A. Gilman is at the High Altitude Observatory, National Center for Atmospheric Research, Post Office Box 3000, Boulder, CO 80303, USA. J. W. Harvey, F. Hill, R. F. Howard, J. W. Leibacher, and J. A. Pintar are at the National Solar Observatory, National Optical Astronomy Observatories (NSO/NOAO), Post Office Box 26732, Tucson, AZ 85726-6732, USA. H. P. Jones is at NASA/Goddard Space Flight Center, Southwest Solar Station, NSO/NOAO, Post Office Box 26732, Tucson, AZ 85726-6732, USA. J. C. Kasher is in the Physics Department, University of Nebraska at Omaha, 64th and Dodge Streets, Omaha, NE 68182-0266, USA. G. W. Simon is at Air Force Materiel Command, Phillips Laboratory, Geophysics Directorate, Solar Research Branch, NSO, Sunspot, NM 88349, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8662460" target="_blank"〉PubMed〈/a〉

Description: The Global Oscillation Network Group (GONG) project estimates the frequencies, amplitudes, and linewidths of more than 250,000 acoustic resonances of the sun from data sets lasting 36 days. The frequency resolution of a single data set is 0.321 microhertz. For frequencies averaged over the azimuthal order m, the median formal error is 0.044 microhertz, and the associated median fractional error is 1.6 x 10(-5). For a 3-year data set, the fractional error is expected to be 3 x 10(-6). The GONG m-averaged frequency measurements differ from other helioseismic data sets by 0.03 to 0.08 microhertz. The differences arise from a combination of systematic errors, random errors, and possible changes in solar structure.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hill -- Stark -- Stebbins -- Anderson -- Antia -- Brown -- Duvall Jr -- Haber -- Harvey -- Hathaway -- Howe -- Hubbard -- Jones -- Kennedy -- Korzennik -- Kosovichev -- Leibacher -- Libbrecht -- Pintar -- Rhodes Jr -- Schou -- Thompson -- Tomczyk -- Toner -- Toussaint -- Williams -- New York, N.Y. -- Science. 1996 May 31;272(5266):1292-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉F. Hill, E. R. Anderson, J. W. Harvey, R. P. Hubbard, J. R. Kennedy, J. W. Leibacher, J. A. Pintar, C. G. Toner, R. Toussaint, and W. E. Williams are with the National Solar Observatory, National Optical Astronomy Observatories (NOAO), Post Office Box 26732, Tucson, AZ 85726-6732, USA. P. B. Stark is with the Department of Statistics and Space Sciences Laboratory, University of California, Berkeley, CA 94720, USA. R. T. Stebbins and D. A. Haber are with JILA, University of Colorado, Boulder, CO 80309, USA. H. M. Antia is with the Tata Institute of Fundamental Research, Bombay, India. T. M. Brown and S. Tomczyk are with the High Altitude Observatory, National Center for Atmospheric Research, Boulder, CO 80307, USA. T. L. Duvall is with the NASA Goddard Space Flight Center, Stanford University, Center for Space Science and Astrophysics (CSSA), Stanford, CA 94305, USA. D. H. Hathaway is with the NASA Marshall Space Flight Center, Mail Code ES82, Huntsville, AL 35812, USA. R. Howe and M. J. Thompson are with the Astronomy Unit, Queen Mary and Westfield College, London E1 4NS, UK. H. P. Jones is with the NASA Goddard Space Flight Center Southwest Station, NOAO, Tucson, AZ 85726, USA. S. G. Korzennik is with the Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA. A. G. Kosovichev and J. Schou are with Stanford University, CSSA, Stanford, CA 94305, USA. K. G. Libbrecht is with the California Institute of Technology, 264-33, Pasadena, CA 91125, USA. E. J. Rhodes is with the Department of Physics and Astronomy, University of Southern California, Los Angeles, CA 90089, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8662457" target="_blank"〉PubMed〈/a〉

Description: Global Oscillation Network Group data reveal that the internal structure of the sun can be well represented by a calibrated standard model. However, immediately beneath the convection zone and at the edge of the energy-generating core, the sound-speed variation is somewhat smoother in the sun than it is in the model. This could be a consequence of chemical inhomogeneity that is too severe in the model, perhaps owing to inaccurate modeling of gravitational settling or to neglected macroscopic motion that may be present in the sun. Accurate knowledge of the sun's structure enables inferences to be made about the physics that controls the sun; for example, through the opacity, the equation of state, or wave motion. Those inferences can then be used elsewhere in astrophysics.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gough -- Kosovichev -- Toomre -- Anderson -- Antia -- Basu -- Chaboyer -- Chitre -- Christensen-Dalsgaard -- Dziembowski -- Eff-Darwich -- Elliott -- Giles -- Goode -- Guzik -- Harvey -- Hill -- Leibacher -- Monteiro -- Richard -- Sekii -- Shibahashi -- Takata -- Thompson -- Vauclair -- Vorontsov -- New York, N.Y. -- Science. 1996 May 31;272(5266):1296-300.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉D. O. Gough, J. R. Elliott, and T. Sekii are with the Institute of Astronomy, University of Cambridge, CB3 0HA, UK. A. G. Kosovichev and P. R. Giles are with HEPL, Stanford University, Stanford, CA, USA. J. Toomre is at JILA, University of Colorado, Boulder, CO, USA. E. Anderson, J. W. Harvey, F. Hill, and J. W. Leibacher are at the National Solar Observatory, Tucson, AZ, USA. H. M. Antia and S. M. Chitre are at the Tata Institute for Fundamental Research, Bombay, India. S. Basu and J. Christensen-Dalsgaard are at the Theoretical Astrophysics Centre, Aarhus University, Denmark. B. Chaboyer is at the Canadian Institute for Theoretical Astrophysics, Toronto, Canada. W. A. Dziembowski is at the Copernicus Astronomical Center, Warsaw, Poland. A. Eff-Darwich is at the Instituto Astrofisico de Canarias, Tenerife, Canary Islands. P. R. Goode is at the New Jersey Institute of Technology, Newark, NJ, USA. J. A. Guzik is at the Los Alamos National Laboratory, Los Alamos, NM, USA. M. J. P. F. G. Monteiro is at the University of Oporto, Postugal. O. Richard and S. Vauclair are at the Observatoire Midi-Pyrenees, Toulouse, France. H. Shibahashi and M. Takata are in the Department of Astronomy, University of Tokyo, Tokyo, Japan. M. J. Thompson and S. V. Vorontsov are at Queen Mary and Westfield College, University of London, London, UK.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8662458" target="_blank"〉PubMed〈/a〉

Description: Splitting of the sun's global oscillation frequencies by large-scale flows can be used to investigate how rotation varies with radius and latitude within the solar interior. The nearly uninterrupted observations by the Global Oscillation Network Group (GONG) yield oscillation power spectra with high duty cycles and high signal-to-noise ratios. Frequency splittings derived from GONG observations confirm that the variation of rotation rate with latitude seen at the surface carries through much of the convection zone, at the base of which is an adjustment layer leading to latitudinally independent rotation at greater depths. A distinctive shear layer just below the surface is discernible at low to mid-latitudes.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Thompson -- Toomre -- Anderson -- Antia -- Berthomieu -- Burtonclay -- Chitre -- Christensen-Dalsgaard -- Corbard -- DeRosa -- Genovese -- Gough -- Haber -- Harvey -- Hill -- Howe -- Korzennik -- Kosovichev -- Leibacher -- Pijpers -- Provost -- Rhodes Jr -- Schou -- Sekii -- Stark -- Wilson -- New York, N.Y. -- Science. 1996 May 31;272(5266):1300-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉M. J. Thompson and R. Howe are in the Astronomy Unit, Queen Mary and Westfield College, University of London, Mile End Road, London E1 4NS, UK. J. Toomre, M. DeRosa, and D. A. Haber are at the Joint Institute for Laboratory Astrophysics, University of Colorado, Boulder, CO 80309-0440, USA. E. R. Anderson, J. W. Harvey, F. Hill, and J. W. Leibacher are at the National Solar Observatory (NSO), National Optical Astronomy Observatories (NOAO), Post Office Box 26732, Tucson, AZ 85726-6732, USA. H. M. Antia and S. M. Chitre are at the Tata Institute of Fundamental Research, Bombay 400005, India. G. Berthomieu, T. Corbard, and J. Provost are at the Observatoire de la Cote d'Azur, 06304 Nice Cedex 4, France. D. Burtonclay and P. R. Wilson are in the School of Mathematics, University of Sydney, Sydney, NSW 2006, Australia. J. Christensen-Dalsgaard and F. P. Pijpers are at the Theoretical Astrophysics Center, Aarhus University, DK-8000 Aarhus C, Denmark. C. R. Genovese is in the Department of Statistics, Carnegie Mellon University, Pittsburgh, PA 15213, USA. D. O. Gough and T. Sekii are in the Institute of Astronomy, University of Cambridge, Cambridge CB3 0HA, UK. S. G. Korzennik is at the Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA. A. G. Kosovichev and J. Schou are at Hansen Experimental Physics Laboratory Annex, Stanford University, Stanford, CA 94305-4085, USA. E. J. Rhodes Jr. is in the Department of Physics and Astronomy, University of Southern California, Los Angeles, CA 90089, USA. P. B. Stark is in the Department of Statistics, University of California, Berkeley, CA 94720-3860, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8662459" target="_blank"〉PubMed〈/a〉

Description: Hydrologic exchange fluxes (HEFs) vary significantly along river corridors due to spatio-temporal changes in discharge and geomorphology. This variability results in the emergence of biogeochemical hot-spots and hot-moments that ultimately control solute and energy transport and ecosystem services from the local to the watershed scales. In this work, we use a reduced-order model to gain mechanistic understanding of river bank storage and sinuosity-driven hyporheic exchange induced by transient river discharge. This is the first time that a systematic analysis of both processes is presented and serves as an initial step to propose parsimonious, physics-based models for better predictions of water quality at the large watershed scale. The effects of channel sinuosity, alluvial valley slope, hydraulic conductivity, and river stage forcing intensity and duration are encapsulated in dimensionless variables that can be easily estimated or constrained. We find that the importance of perturbations in the hyporheic zone's flux, residence times, and geometry is mainly explained by two dimensionless variables representing the ratio of the hydraulic time constant of the aquifer and the duration of the event (Γ d ) and the importance of the ambient groundwater flow (Δ h *). Our model additionally shows that even systems with small sensitivity, resulting in small changes in the hyporheic zone extent, are characterized by highly variable exchange fluxes and residence times. These findings highlight the importance of including dynamic changes in hyporheic zones for typical HEF models such as the transient storage model.