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Satellite synthetic-aperture radar (SAR) Interferometry is employed to map the hinge line, or limit of tidal flexing, of Rutford Ice Stream and Carlson Inlet, Antarctica, and detect its migration between 1992 and 1996. The hinge line is mapped using a model fit from an elastic beam theory.
We have examined the ISEE-3 distant tail data during three intense (Dst< -100(sub n)T) magnetic storms and have identified the tail response to high speed solar wind streams, interplanetary magnetic clouds, and near-Earth storms. The three storms have a peak Dst ranging from -150 to -220 nT, and occur on Jan. 9, Feb. 4, and Aug. 8, 1993.
This paper compares the performances of two different types of data-derived symbol synchronizers, namely, Filter and Square (FS) and Digital Data Transition Tracking Loop (DTTL), in the presence of unbalanced data streams.
Ocean backscatter signatures were measured by the Jet Propulsion Laboratory airborne NUSCAT K(sub u)-band scatterometer across the Gulf Stream sea surface temperature front. The measurements were made during the Surface Wave Dynamics Experiment (SWADE) off the coast of Virginia and Maryland in the winter of 1991.
Measurements of the specific entropy argument of solar wind protons, T/n superscript y-1, reveal that nearly every occurrence of a high-speed stream seen at Ulysses in 1992-3 is characterized by an abrupt interface at its trailing edge.
This paper indicates that topography, Rossby wave dynamics, and eddy/stream interactions, all appear to have a significant role in determining the space-time scales and propagation properties of the long-period response of sea level in the Gulf Stream.
This fact sheet explores the more than 65 gigawatts (GW) of sustainable hydropower potential in U.S. stream-reaches, according to the hydropower resource assessment funded by DOE and executed by Oak Ridge National Laboratory.
The Waste Information Management System (WIMS) 2012-13 was updated to support the Department of Energy (DOE) accelerated cleanup program. The schedule compression required close coordination and a comprehensive review and prioritization of the barriers that impeded treatment and disposition of the waste streams at each site. Many issues related to waste treatment and disposal were potential critical path issues under the accelerated schedule. In order to facilitate accelerated cleanup initiatives, waste managers at DOE field sites and at DOE Headquarters in Washington, D.C., needed timely waste forecast and transportation information regarding the volumes and types of radioactive waste that would be generated by DOE sites over the next 40 years. Each local DOE site historically collected, organized, and displayed waste forecast information in separate and unique systems. In order for interested parties to understand and view the complete DOE complex-wide picture, the radioactive waste and shipment information of each DOE site needed to be entered into a common application. The WIMS application was therefore created to serve as a common application to improve stakeholder comprehension and improve DOE radioactive waste treatment and disposal planning and scheduling. WIMS allows identification of total forecasted waste volumes, material classes, disposition sites, choke points, technological or regulatory barriers to treatment and disposal, along with forecasted waste transportation information by rail, truck and inter-modal shipments. The Applied Research Center (ARC) at Florida International University (FIU) in Miami, Florida, developed and deployed the web-based forecast and transportation system and is responsible for updating the radioactive waste forecast and transportation data on a regular basis to ensure the long-term viability and value of this system. (authors)
The need to control emissions of the gaseous radionuclides to the air during nuclear fuel recycling is widely recognized. Gaseous radionuclides can partition to off-gas streams emanating from the various individual processes used in the recycle plant, such as from the mechanical head end (shear), tritium pretreatment, fuel dissolver, vessel vents, cell ventilation, and conversion operations. In traditional recycle plants, the bulk of the four primary volatile fission products (i.e., {sup 3}H, {sup 14}C, {sup 85}Kr, and {sup 129}I) is released in the head-end processes, for example, the dissolution process. The usual off-gas treatment sequence of operations targets removal of tritium (as {sup 3}HHO), iodine, carbon (as {sup 14}CO{sub 2}), and the noble gases, in that order. Water and iodine are captured first because the other species are relatively unimpeded by the sorbents used for water and iodine, so they flow downstream to additional treatment processes. Water and iodine do react with one another, and many techniques used to collect one of these species also collect some fraction of the other. It is quite desirable to sequester the iodine and water separately because the tritiated water may be disposed of as a low level waste. If not cleanly separated, contamination of the low-level waste by iodine may elevate its classification to high-level waste and result in greater costs for disposal. The proposed sorption sequence was tested in the laboratory. Use of a second column of AgZ permits the detection of breakthrough from the primary AgZ column while protecting the downstream 3AMS column from collecting iodine. (This arrangement is equivalent to enabling intra-column sampling of the primary column.) Neutron activation analysis of the 3AMS revealed that iodine was below, or at, the level of detection. The results successfully demonstrated that iodine can be sequestered in the AgZ while the water is collected free of iodine in the 3AMS column. (authors)
The Waste Information Management System (WIMS) 2018-19 was updated to support the Department of Energy (DOE) accelerated cleanup program. The schedule compression required close coordination and a comprehensive review and prioritization of the barriers that impeded treatment and disposition of the waste streams at each site. Many issues related to waste treatment and disposal were potential critical path issues under the accelerated schedule. In order to facilitate accelerated cleanup initiatives, waste managers at DOE field sites and at DOE Headquarters in Washington, D.C., needed timely waste forecast and transportation information regarding the volumes and types of radioactive waste that would be generated by DOE sites over the next 35 years. Each local DOE site historically collected, organized, and displayed waste forecast information in separate and unique systems. In order for interested parties to understand and view the complete DOE complex-wide picture, the radioactive waste and shipment information of each DOE site needed to be entered into a common application. The WIMS application was therefore created to serve as a common application to improve stakeholder comprehension and improve DOE radioactive waste treatment and disposal planning and scheduling. WIMS allows identification of total forecasted waste volumes, material classes, disposition sites, choke points, technological or regulatory barriers to treatment and disposal, along with forecasted waste transportation information by rail, truck and intermodal shipments. The Applied Research Center (ARC) at Florida International University (FIU) in Miami, Florida, developed and deployed the web-based forecast and transportation system and is responsible for updating the radioactive waste forecast and transportation data on a regular basis to ensure the long-term viability and value of this system. (authors)
Abstract The subauroral polarization streams (SAPS) are one of the most important features in representing magnetosphere‐ionosphere coupling processes. In this study, we use a state‐of‐the‐art modeling framework that couples an inner magnetospheric ring current model RAM‐SCB with a global MHD model Block‐Adaptive Tree Solar‐wind Roe Upwind Scheme (BATS‐R‐US) and an ionospheric potential solver to study the SAPS that occurred during the 17 March 2013 storm event as well as to assess the modeling capability. Both ionospheric and magnetospheric signatures associated with SAPS are analyzed to understand the spatial and temporal evolution of the electrodynamics in the midlatitude regions. Results show that the model captures the SAPS at subauroral latitudes, where Region 2 field‐aligned currents (FACs) flow down to the ionosphere and the conductance is lower than in the higher‐latitude auroral zone. Comparisons to observations such as FACs observed by Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE), cross‐track ion drift from Defense Meteorological Satellite Program (DMSP), and in situ electric field observations from the Van Allen Probes indicate that the model generally reproduces the global dynamics of the Region 2 FACs, the position of SAPS along the DMSP, and the location of the SAPS electric field around L of 3.0 in the inner magnetosphere near the equator. The model also demonstrates double westward flow channels in the dusk sector (the higher‐latitude auroral convection and the subauroral SAPS) and captures the mechanism of the SAPS. However, the comparison with ion drifts along DMSP trajectories shows an underestimate of the magnitude of the SAPS and the sensitivity to the specific location and time. The comparison of the SAPS electric field with that measured from the Van Allen Probes shows that the simulated SAPS electric field penetrates deeper than in reality, implying that the shielding from the Region 2 FACs in the model is not well represented. Possible solutions in future studies to improve the modeling capability include implementing a self‐consistent ionospheric conductivity module from inner magnetosphere particle precipitation, coupling with the thermosphere‐ionosphere chemical processes, and connecting the ionosphere with the inner magnetosphere by the stronger Region 2 FACs calculated in the inner magnetosphere model.
During early November 2013, the magnetosphere experienced concurrent driving by a coronal mass ejection (CME) during an ongoing high-speed stream (HSS) event. The relativistic electron response to these two kinds of drivers, i.e., HSS and CME, is typically different, with the former often leading to a slower buildup of electrons at larger radial distances, while the latter energizing electrons rapidly with flux enhancements occurring closer to the Earth. In this paper, we present a detailed analysis of the relativistic electron response including radial profiles of phase space density as observed by both Magnetic Electron and Ion Sensor (MagEIS) and Relativistic Electron Proton Telescope instruments on the Van Allen Probes mission. Data from the MagEIS instrument establish the behavior of lower energy (<1 MeV) electrons which span both intermediary and seed populations during electron energization. Measurements characterizing the plasma waves and magnetospheric electric and magnetic fields during this period are obtained by the Electric and Magnetic Field Instrument Suite and Integrated Science instrument on board Van Allen Probes, Search Coil Magnetometer and Flux Gate Magnetometer instruments on board Time History of Events and Macroscale Interactions during Substorms, and the low-altitude Polar-orbiting Operational Environmental Satellites. These observations suggest that during this time period, both radial transport and local in situ processes are involved in the energization of electrons. Finally, the energization attributable to radial diffusion is most clearly evident for the lower energy (<1 MeV) electrons, while the effects of in situ energization by interaction of chorus waves are prominent in the higher-energy electrons.
Abstract Path analyses of historical streamflow data from the Pacific Northwest indicate that the precipitation amount has been the dominant control on the magnitude of low streamflow extremes compared to the air temperature‐affected timing of snowmelt runoff. The relative sensitivities of low streamflow to precipitation and temperature changes have important implications for adaptation planning because global circulation models produce relatively robust estimates of air temperature changes but have large uncertainties in projected precipitation amounts in the Pacific Northwest U.S. Quantile regression analyses indicate that low streamflow extremes from the majority of catchments in this study have declined from 1948 to 2013, which may significantly affect terrestrial and aquatic ecosystems, and water resource management. Trends in the 25th percentile of mean annual streamflow have declined and the center of timing has occurred earlier. We quantify the relative influences of total precipitation and air temperature on the annual low streamflow extremes from 42 stream gauges using mean annual streamflow as a proxy for precipitation amount effects and streamflow center of timing as a proxy for temperature effects on low flow metrics, including 7q10 summer (the minimum 7 day flow during summer with a 10 year return period), mean August , mean September , mean summer , 7q10 winter , and mean winter flow metrics. These methods have the benefit of using only readily available streamflow data, which makes our results robust against systematic errors in high elevation distributed precipitation data. Winter low flow metrics are weakly tied to both mean annual streamflow and center of timing .
This paper examines the sensitivity to a change in sea surface temperature (SST) resolution of the interaction between atmospheric and oceanic fronts in the Gulf Stream region in the ERA-Interim reanalysis data set. Two periods are considered, January 1979 to December 2001 (SST resolution 1° × 1°) and December 2010 to February 2016 (SST resolution 0.05° × 0.05°). The winter season from the latter 6 years of high-resolution SST is compared against six random periods of six wintertime seasons from the low-resolution SST period, to assess the robustness of the result against natural climate variability. In all comparisons, a significant change in frontal air-sea sensible heat flux exchange is found that is highly correlated to the change in mean SST gradient. This leads to both increases and decreases in occurrence of atmospheric fronts and mean precipitation of up to 30%. These results reemphasize the importance of high SST resolution in resolving the influence of oceanic fronts on weather and climate.
Novel dividing wall columns (DWCs) can be obtained by converting thermal couplings to liquid-only transfer streams. We develop a simple four-step method to generate a complete set of DWCs containing n - 2 dividing walls, for a given n-component fully thermally coupled (FTC) distillation. Among the novel DWCs, some easy-to-operate DWCs possess the property that the vapor flow in every section of the DWC can be controlled during operation by means that are external to the column. We develop a simple method to enumerate all such easy-to-operate DWCs. We expect that the easy-to-operate DWCs can be operated close-to-optimality; leading to a successful industrial implementation of the n-component (n ≥ 3) FTC distillation in the form of a DWC. As an illustration, we show figures of all easy-to-operate DWCs with two dividing walls for the four-component FTC distillation.
Abstract Subsidy–stress gradients offer a useful framework for understanding ecological responses to perturbation and may help inform ecological metrics in highly modified systems. Historic, region‐wide shifts from bottomland hardwood forest to row crop agriculture can cause positively skewed impact gradients in alluvial plain ecoregions, resulting in tolerant organisms that typically exhibit a subsidy response (increased abundance in response to environmental stressors) shifting to a stress response (declining abundance at higher concentrations). As a result, observed biological tolerance in modified ecosystems may differ from less modified regions, creating significant challenges for detecting biological responses to restoration efforts. Using the agriculturally dominated Mississippi Alluvial Plain (MAP) ecoregion in Mississippi, USA, as a case study, we tested the hypothesis that macroinvertebrate taxa that typically display a subsidy response to nutrient enrichment in less modified ecoregions (i.e., nutrient‐tolerance) shift to a stress response to increasing nutrients in highly modified watersheds with elevated baseline nutrient conditions (i.e., nutrient intolerance). The abundance and diversity of MAP‐specific intolerant taxa identified with threshold indicator taxa analysis were either unresponsive or exhibited a subsidy response to increasing nutrients in less modified ecoregions in Mississippi with less land alteration and lower nutrient concentrations, but declined at higher concentrations, providing evidence for a stress response to elevated nutrients in the MAP. Additionally, MAP‐specific tolerant and intolerant taxa richness responded to increased nutrients predictably and consistently across space and time within the MAP. However, in MAP streams, elevated specific conductance was predicted to dampen the response of tolerant and intolerant taxa richness to increasing nutrient concentrations, highlighting the importance of considering multistressor interactions when interpreting biological data. Lastly, we demonstrate the efficacy of this approach with sediment bacterial communities characterized with amplicon sequencing, which lack sufficient life history characteristics necessary for the development of multimetric indices. Both macroinvertebrate and bacterial communities responded similarly to increasing nutrient concentrations, suggesting DNA‐based approaches may provide an efficient biological assessment tool for monitoring water quality improvements in highly modified watersheds.
This project demonstrates the successful use of small unoccupied aircraft system (sUASs) for hydrogeological characterization of a remote stream reach in a rugged mountain terrain. Thermal infrared, visual imagery, and derived digital surface models are used to inform conceptual models of groundwater/surface–water exchange and efficiently geolocate zones of preferential groundwater discharge that can be quantified using various ground–based methodology.
Application of high-frequency monitoring of dissolved organic carbon (DOC) is difficult in instances where training datasets are challenging to develop (e.g., remote locations) and the relationship between optical features and DOC concentration changes due to environmental or landscape shifts (e.g., climate or land-use change). We developed and compared three partial least squares (PLS) models using in situ water level measurements, conductivity, and UV–Vis spectral attenuation to predict DOC. Two site-specific models were developed using data from a hillslope-dominated forest or a low-relief wetland-pond-dominated stream catchment. The third model, using data from both sites, exhibited the best performance (DOC range = 4–15.5 mg C L −1 , mean = 8.38 mg C L −1 , training RMSE = 0.34 mg C L −1 , internal validation RMSE = 0.50 mg C L −1 , external validation RMSE = 2.43 mg C L −1 ). We further demonstrate using PLS model statistics to monitor performance and elucidate when and how models should be updated. These statistics, Hotelling's T 2 and squared prediction errors, are useful consistency checks for the predictions made and detect underlying inconsistencies that, if undetected, can reduce the robustness of DOC prediction. For example, via the T 2 statistic, we identified the summer–autumn transition as a period when DOC composition differed from what was represented in the training dataset. We also determined that elevated SUVA 254 values contributed to the overall bias observed in predictions made during the subsequent year as part of the external validation. This enabled the application of a bias correction that reduced the RMSE from 2.43 to 0.89 mg C L −1 . The method presented here could be applied to future monitoring programs enabling model updates to monitor DOC fluxes accurately from optical datasets (e.g., attenuance or fluorescence) in the face of developing datasets in remote locations or environmental change. In conclusion, implementation of this approach may also identify possible regime shifts or landscape and hydrologic change associated with climate and other environmental changes relevant to terrestrial to aquatic fluxes.