bluuebunny/crossref_metadata_2025 huggingface dataset:
Isolating the Liquid Cloud Response to Recent Arctic Sea Ice Variability Using Spaceborne Lidar Observations
Authors: Morrison A. L. , Kay J. E. , Chepfer H. , Guzman R. , Yettella V.
Published: January 2018

While the radiative influence of clouds on Arctic sea ice is known, the influence of sea ice cover on Arctic clouds is challenging to detect, separate from atmospheric circulation, and attribute to human activities. Providing observational constraints on the two‐way relationship between sea ice cover and Arctic clouds is important for predicting the rate of future sea ice loss. Here we use 8 years of CALIPSO (Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observations) spaceborne lidar observations from 2008 to 2015 to analyze Arctic cloud profiles over sea ice and over open water. Using a novel surface mask to restrict our analysis to where sea ice concentration varies, we isolate the influence of sea ice cover on Arctic Ocean clouds. The study focuses on clouds containing liquid water because liquid‐containing clouds are the most important cloud type for radiative fluxes and therefore for sea ice melt and growth. Summer is the only season with no observed cloud response to sea ice cover variability: liquid cloud profiles are nearly identical over sea ice and over open water. These results suggest that shortwave summer cloud feedbacks do not slow long‐term summer sea ice loss. In contrast, more liquid clouds are observed over open water than over sea ice in the winter, spring, and fall in the 8 year mean and in each individual year. Observed fall sea ice loss cannot be explained by natural variability alone, which suggests that observed increases in fall Arctic cloud cover over newly open water are linked to human activities.
Key Role of Nitrate in Phase Transitions of Urban Particles: Implications of Important Reactive Surfaces for Secondary Aerosol Formation
Authors: Sun Jiaxing , Liu Lei , Xu Liang , Wang Yuanyuan , Wu Zhijun , Hu Min , Shi Zongbo , Li Yongjie , Zhang Xiaoye , Chen Jianmin , Li Weijun
Published: January 2018

Ammonium sulfate (AS) and ammonium nitrate (AN) are key components of urban fine particles. Both field and model studies showed that heterogeneous reactions of SO2, NO2, and NH3 on wet aerosols accelerated the haze formation in northern China. However, little is known on phase transitions of AS‐AN containing haze particles. Here hygroscopic properties of laboratory‐generated AS‐AN particles and individual particles collected during haze events in an urban site were investigated using an individual particle hygroscopicity system. AS‐AN particles showed a two‐stage deliquescence at mutual deliquescence relative humidity (MDRH) and full deliquescence relative humidity (DRH) and three physical states: solid before MDRH, solid‐aqueous between MDRH and DRH, and aqueous after DRH. During hydration, urban haze particles displayed a solid core and aqueous shell at RH = 60–80% and aqueous phase at RH > 80%. Most particles were in aqueous phase at RH > 50% during dehydration. Our results show that AS content in individual particles determines their DRH and AN content determines their MDRH. AN content increase can reduce MDRH, which indicates occurrence of aqueous shell at lower RH. The humidity‐dependent phase transitions of nitrate‐abundant urban particles are important to provide reactive surfaces of secondary aerosol formation in the polluted air.
Observations and Explicit Modeling of Summertime Carbonyl Formation in Beijing: Identification of Key Precursor Species and Their Impact on Atmospheric Oxidation Chemistry
Authors: Yang Xue , Xue Likun , Wang Tao , Wang Xinfeng , Gao Jian , Lee Shuncheng , Blake Donald R. , Chai Fahe , Wang Wenxing
Published: January 2018

Carbonyls are an important group of volatile organic compounds (VOCs) that play critical roles in tropospheric chemistry. To better understand the formation mechanisms of carbonyl compounds, extensive measurements of carbonyls and related parameters were conducted in Beijing in summer 2008. Formaldehyde (11.17 ± 5.32 ppbv), acetone (6.98 ± 3.01 ppbv), and acetaldehyde (5.27 ± 2.24 ppbv) were the most abundant carbonyl species. Two dicarbonyls, glyoxal (0.68 ± 0.26 ppbv) and methylglyoxal (MGLY; 1.10 ± 0.44 ppbv), were also present in relatively high concentrations. An observation‐based chemical box model was used to simulate the in situ production of formaldehyde, acetaldehyde, glyoxal, and MGLY and quantify their contributions to ozone formation and ROx budget. All four carbonyls showed similar formation mechanisms but exhibited different precursor distributions. Alkenes (mainly isoprene and ethene) were the dominant precursors of formaldehyde, while both alkenes (e.g., propene, i‐butene, and cis‐2‐pentene) and alkanes (mainly i‐pentane) were major precursors of acetaldehyde. For dicarbonyls, both isoprene and aromatic VOCs were the dominant parent hydrocarbons of glyoxal and MGLY. Photolysis of oxygenated VOCs was the dominant source of ROx radicals (approximately >80% for HO2 and approximately >70% for RO2) in Beijing. Ozone production occurred under a mixed‐control regime with carbonyls being the key VOC species. Overall, this study provides some new insights into the formation mechanisms of carbonyls, especially their parent hydrocarbon species, and underlines the important role of carbonyls in radical chemistry and ozone pollution in Beijing. Reducing the emissions of alkenes and aromatics would be an effective way to mitigate photochemical pollution in Beijing.
Decoupling of Climatic Drying and Asian Dust Export During the Holocene
Authors: Xu Bing , Wang Luo , Gu Zhaoyan , Hao Qingzhen , Wang Haizhi , Chu Guoqiang , Jiang Dabang , Liu Qiang , Qin Xiaoguang
Published: January 2018

Both paleoclimatic records and models suggest that the dust accumulation in ice cores and marine sediments, which is often regarded as a direct record of changing atmospheric dust loading and used to estimate its climatic impact, is strongly coupled to the aridity of dust source regions. However, the underlying association of this couple has not been tested directly because of the lack of continuous and well‐dated independent records of eolian activity in dust source regions. Here we present a high‐resolution multiproxy record of the Holocene eolian activity and climate changes from Lake Xiarinur in north China, a major Asian dust source region. Our data, together with the records of Asian dust accumulation in downwind areas, including the North Pacific Ocean and Greenland, suggest a decoupling between long‐distant Asian dust export and climatic drying in the Holocene. Although the climate was humid and the eolian activity was weak in the source region during the early Holocene, the dust accumulation in the North Pacific Ocean and Greenland was relatively high. Similarly, while climatic drying and strong eolian activity occurred in north China during the late Holocene, the rate of dust accumulation in the downwind areas was low. The long‐distant export of Asian dust is closely correlated with the strength of the Siberian High rather than the westerlies as widely believed before. The rate of dust accumulation in the GISP2 Greenland ice core is comparable in patterns with the intensity of the Siberian High forced eolian activity on both millennial and centennial time scales.
Sources, Load, Vertical Distribution, and Fate of Wintertime Aerosols North of Svalbard From Combined V4 CALIOP Data, Ground‐Based IAOOS Lidar Observations and Trajectory Analysis
Authors: Di Biagio C. , Pelon J. , Ancellet G. , Bazureau A. , Mariage V.
Published: January 2018

We have analyzed aerosol properties at the regional scale over high Arctic north of Svalbard between October 2014 and June 2015 from version 4 (V4) CALIOP (Cloud and Aerosol Lidar with Orthogonal Polarization) spaceborne observations and compared results with surface lidar observations from IAOOS (Ice‐Atmosphere‐Ocean Observing System) platforms. CALIOP data indicate a maximum in aerosol occurrence at the end of winter attributed to low‐level (0–2 km) and midtropospheric (2–5 km) particles identified in CALIOP V4 product as being mostly of dust origin. Another maximum was observed in October–December attributed to clean marine particles below 2 km and smoke and dust above. The 532 nm aerosol extinction was in the range 1–8 Mm−1 (0–2 km), 1–18 Mm−1 (2–5 km), and 0–6 Mm−1 (5–10 km), a factor 2 lower compared to values previously reported using CALIOP V3 data set. Aerosols are identified from trajectory analyses to originate mostly from Russia/Europe at all altitudes, and also North America above 2 km, and it is concluded that dust and clean marine types are most probably overrepresented in the analyzed CALIOP data set. It is proposed that most part of dust types are diamond dust, while part of clean marine are polluted species, as corroborated from colocated polarized lidar IAOOS observations. IAOOS observations allowed confirming the identified sensitivity of CALIOP with a particle backscatter coefficient of ~0.001 km−1 sr−1 at 532 nm. For optically thicker layers CALIOP is shown to be a valuable tool to follow transport of aerosol layers in the Arctic and identify their possible modifications.
Strength, Depth, and Geometry of Magnetic Sources in the Crust of the Moon From Localized Power Spectrum Analysis
Authors: Wieczorek Mark A.
Published: January 2018

Spacecraft observations show that weak magnetic fields of crustal origin are ubiquitous across the surface of the Moon. To investigate the origin of these magnetic anomalies, a model was developed for the magnetic power spectrum that consists of ensembles of randomly magnetized sills or prisms. Localized spectrum analyses constrained how the parameters of this model vary with position, including the size of the sources, a quantity proportional to their mean‐squared dipole moment, and the depth to the top and bottom of the magnetized region. The depth to the top of the magnetized region varies from the surface to about 25 km. The magnetic carriers in the deep crust likely formed at the same time as the crust itself, implying that a core‐generated dynamo field must have existed when the crust was cooling during the first 100 Myr of lunar evolution. The parameter related to the strength of magnetization shows the existence of a prominent region on the nearside hemisphere that is largely unmagnetized and that correlates with a region of extremely low surface field strengths. This region lies entirely within a geological province that is highly enriched in heat‐producing elements (the Procellarum KREEP Terrane), suggesting that this region escaped being magnetized because of prolonged high crustal temperatures. The nearside magnetic low may be representative of the size of that portion of the crust that is highly enriched in heat‐producing elements, which is almost one third the size of the Procellarum KREEP Terrane based on surface thorium abundances.
Equatorial Oscillation and Planetary Wave Activity in Saturn's Stratosphere Through the Cassini Epoch
Authors: Guerlet S. , Fouchet T. , Spiga A. , Flasar F. M. , Fletcher L. N. , Hesman B. E. , Gorius N.
Published: January 2018

Thermal infrared spectra acquired by Cassini/Composite InfraRed Spectrometer (CIRS) in limb‐viewing geometry in 2015 are used to derive 2‐D latitude‐pressure temperature and thermal wind maps. These maps are used to study the vertical structure and evolution of Saturn's equatorial oscillation (SEO), a dynamical phenomenon presenting similarities with the Earth's quasi‐biennal oscillation (QBO) and semi‐annual oscillation (SAO). We report that a new local wind maximum has appeared in 2015 in the upper stratosphere and derive the descent rates of other wind extrema through time. The phase of the oscillation observed in 2015, as compared to 2005 and 2010, remains consistent with a ∼15 year period. The SEO does not propagate downward at a regular rate but exhibits faster descent rate in the upper stratosphere, combined with a greater vertical wind shear, compared to the lower stratosphere. Within the framework of a QBO‐type oscillation, we estimate the absorbed wave momentum flux in the stratosphere to be on the order of ∼7 × 10−6 N m−2. On Earth, interactions between vertically propagating waves (both planetary and mesoscale) and the mean zonal flow drive the QBO and SAO. To broaden our knowledge on waves potentially driving Saturn's equatorial oscillation, we searched for thermal signatures of planetary waves in the tropical stratosphere using CIRS nadir spectra. Temperature anomalies of amplitude 1–4 K and zonal wave numbers 1 to 9 are frequently observed, and an equatorial Rossby (n = 1) wave of zonal wave number 3 is tentatively identified in November 2009.
Physical Conditions of Fast Glacier Flow: 2. Variable Extent of Anisotropic Ice and Soft Basal Sediment From Seismic Reflection Data Acquired on Store Glacier, West Greenland
Authors: Hofstede C. , Christoffersen P. , Hubbard B. , Doyle S. H. , Young T. J. , Diez A. , Eisen O. , Hubbard A.
Published: January 2018

Outlet glaciers of the Greenland Ice Sheet transport ice from the interior to the ocean and contribute directly to sea level rise because discharge and ablation often exceed the accumulation. To develop a better understanding of these fast‐flowing glaciers, we investigate the basal conditions of Store Glacier, a large outlet glacier flowing into Uummannaq Fjord in west Greenland. We use two crossing seismic profiles acquired near the centerline, 30 km upstream of the calving front, to interpret the physical nature of the ice and bed. We identify one notably englacial and two notably subglacial seismic reflections on both profiles. The englacial reflection represents a change in crystal orientation fabric, interpreted to be the Holocene‐Wisconsin transition. From Amplitude‐Versus‐Angle (AVA) analysis we infer that the deepest ∼80 m of ice of the parallel‐flow profile below this reflection is anisotropic with an enhancement of simple shear of ∼2. The ice is underlain by ∼45 m of unconsolidated sediments, below which there is a strong reflection caused by the transition to consolidated sediments. In the across‐flow profile subglacial properties vary over small scale and the polarity of the ice‐bed reflection switches from positive to negative. We interpret these as patches of different basal slipperiness associated with variable amounts of water. Our results illustrate variability in basal properties, and hence ice‐bed coupling, at a spatial scale of ∼100 m, highlighting the need for direct observations of the bed to improve the basal boundary conditions in ice‐dynamic models.
Stable Carbon Isotopes Reveal Soil‐Stream DIC Linkages in Contrasting Headwater Catchments
Authors: Campeau A. , Bishop K. , Nilsson M. B. , Klemedtsson L. , Laudon H. , Leith F. I. , Öquist M. , Wallin M. B.
Published: January 2018

Large CO2 evasion to the atmosphere occurs as dissolved inorganic carbon (DIC) is transported from soils to streams. While this physical process has been the focus of multiple studies, less is known about the underlying biogeochemical transformations that accompany this transfer of C from soils to streams. Here we used patterns in stream water and groundwater δ13C‐DIC values within three headwater catchments with contrasting land cover to identify the sources and processes regulating DIC during its transport. We found that although considerable CO2 evasion occurs as DIC is transported from soils to streams, there were also other processes affecting the DIC pool. Methane production and mixing of C sources, associated with different types and spatial distribution of peat‐rich areas within each catchment, had a significant influence on the δ13C‐DIC values in both soils and streams. These processes represent an additional control on δ13C‐DIC values and the catchment‐scale cycling of DIC across different northern landscape types. The results from this study demonstrate that the transport of DIC from soils to streams results in more than just rapid CO2 evasion to the atmosphere but also represents a channel of C transformation, which questions some of our current conceptualizations of C cycling at the landscape scale.
Assessing the Extent and Impact of Online Data Sharing in Eddy Covariance Flux Research
Authors: Dai Sheng‐Qi , Li Hong , Xiong Jun , Ma Jun , Guo Hai‐Qiang , Xiao Xiangming , Zhao Bin
Published: January 2018

Research data sharing is appealing for its potential benefits on sharers' scientific impact and is also advocated by various policies. How do scientific benefits and policies correlate with practical ecological data sharing? In this study, we investigated data‐sharing practices in eddy covariance flux research as a typical case. First, we collected researchers' data‐sharing information from major observation networks. Then, we downloaded bibliometric data from the Web of Science and evaluated scientific impact using LeaderRank, a synthetic algorithm that takes both citation and cooperation impacts into consideration. Our results demonstrated the following: (1) specific to eddy covariance flux research, 8% of researchers published information in public data portals, whereas 64% of researchers provided their available data online in a downloadable form; (2) regional differences in data sharing, publications, and observation networks existed; and (3) the data sharers in impact‐ranked ecologists followed a long‐tail distribution, which suggested that, although sharing data is not necessary for researchers to be influential, data sharers are more likely to be high‐impact researchers. Differentiated policies should be proposed to encourage ecologists in the long tail of data sharers, and from regions with little tradition of data sharing, to embrace a more open model of science.
Water Shortage Drives Interactions Between Cushion and Beneficiary Species Along Elevation Gradients in Dry Himalayas
Authors: Ale Rita , Zhang Lin , Li Xiang , Raskoti Bhakta Bahadur , Pugnaire Francisco I. , Luo Tianxiang
Published: January 2018

It is challenging to understand the drivers of plant‐plant interaction patterns in dry mountains. However, such knowledge is important to assess alpine ecosystem resilience to climate change. In water‐limited ecosystems, leaf δ13C and satellite‐derived vegetation index (NDVI) may serve as reliable indicators of environmental severity to address plant responses to water availability. We hypothesized that in dry mountains, interaction intensity between cushion and beneficiary species increases with increasing δ13C and decreasing NDVI regardless of elevation, indicating the importance of water availability in driving plant interactions. We used relative interaction indices (RII) of species and individual numbers within and outside the canopy of three cushion plant species along three elevational transects in dry Himalayas, Nepal. Site‐specific NDVI was calculated from 30 m Landsat images. Thornthwaite moisture index was calculated for each elevation site. We observed nonlinear patterns in RII, δ13C, and NDVI with elevation. Intraspecific variation of δ13C was negatively correlated with moisture index and NDVI, while NDVI across sites was positively correlated with precipitation but not with temperature. RII within a cushion species was positively correlated with δ13C and negatively with NDVI when the effect of elevation was removed. In pooled data across cushion species and sites, RII was negatively correlated with precipitation and NDVI when the effect of temperature was removed. RII was uncorrelated with cushion size under the same environment. Leaf nitrogen showed no correlation with RII or δ13C. Our data show that water shortage is the main driver of plant interactions in the alpine belt of dry Himalayas.
Oceanographic and Climatic Change in the Bering Sea, Last Glacial Maximum to Holocene
Authors: Pelto Ben M. , Caissie Beth E. , Petsch Steven T. , Brigham‐Grette Julie
Published: January 2018

Post‐glacial sea level rise led to a direct connection between the Arctic and Pacific Oceans via the Bering Strait. Consequently, the Bering Sea experienced changes in connectivity, size, and sediment sources that were among the most drastic of any ocean basin in the past 30,000 years. However, the sedimentary response to the interplay between climate change and sea level rise in high‐latitude settings such as Beringia remains poorly resolved. To ascertain changes in sediment delivery, productivity, and regional oceanography from the Last Glacial Maximum (LGM) to the Holocene, we analyzed sedimentological, geochemical, and isotopic characteristics of three sediment cores from the Bering Sea. Interpretations of productivity, terrestrial input, nutrient utilization, and circulation are based on organic carbon isotopes (δ13Corg), total organic carbon (TOC), bulk nitrogen isotopes, total organic nitrogen, carbon/nitrogen ratios, elemental X‐ray fluorescence data, grain size, and presence of laminated or dysoxic, green intervals. Principal component analysis of these data captures key climatic intervals. The LGM was characterized by low productivity across the region. In the Bering Sea, deglaciation began around 18–17 ka, with increasing terrestrial sediment and TOC input. Marine productivity increased during the Bølling‐Allerød when laminated sediments revealed dysoxic bottom waters where denitrification was extreme. The Younger Dryas manifested increased terrestrial input and decreased productivity, in contrast with the Pre‐Boreal, when productivity markedly rebounded. The Pre‐Boreal and Bølling‐Allerød were similarly productive, but changes in the source of TOC and a δ13Corg depletion suggest the influence of a gradually flooding Bering Shelf during the Pre‐Boreal and Holocene.
Detrital Zircon Record of a Mesozoic Collisional Forearc Basin in South Central Alaska: The Tectonic Transition From an Oceanic to Continental Arc
Authors: Stevens Goddard Andrea L. , Trop Jeffrey M. , Ridgway Kenneth D.
Published: January 2018

The collision of oceanic arcs with continental margins is an important mechanism for the growth of continents. Ancient forearc basin strata in collisional orogens provide a record of the upper crustal response to this tectonic process. In south central Alaska, Mesozoic forearc basin strata are exposed in a complete crustal section. U‐Pb detrital zircon geochronology from the forearc basin strata was analyzed within a ~107 Ma stratigraphic framework. The Jurassic strata contain unimodal detrital zircon populations that become progressively younger upsection and range from 175 to 151 Ma. These strata are derived from the active oceanic Talkeetna arc. The Cretaceous strata were deposited above multiple unconformities that collectively represent as much as ~30 Ma of nondeposition and/or erosion in the forearc basin. Erosion in the forearc basin and a general absence of detrital zircon ages between 140 and 120 Ma are interpreted as a hiatus of magmatism triggered by collision of the oceanic arc with the former continental margin. The Cretaceous strata have two main detrital zircon populations: a Cretaceous population ranging from 90 to 68 Ma that becomes progressively younger upsection and a Jurassic population with a broad range of peak ages from 194 to 144 Ma. The Cretaceous population marks the establishment of an active Cretaceous continental arc following the collisional event, and the older population reflects continued erosion of the remnant Jurassic oceanic arc plutons. Our results show that detrital zircon geochronology provides a powerful approach for delineating stages of forearc basin collision and the erosion of multiple magmatic arcs.
High‐Elevation Evapotranspiration Estimates During Drought: Using Streamflow and NASA Airborne Snow Observatory SWE Observations to Close the Upper Tuolumne River Basin Water Balance
Authors: Henn Brian , Painter Thomas H. , Bormann Kat J. , McGurk Bruce , Flint Alan L. , Flint Lorraine E. , White Vince , Lundquist Jessica D.
Published: January 2018

Hydrologic variables such as evapotranspiration (ET) and soil water storage are difficult to observe across spatial scales in complex terrain. Streamflow and lidar‐derived snow observations provide information about distributed hydrologic processes such as snowmelt, infiltration, and storage. We use a distributed streamflow data set across eight basins in the upper Tuolumne River region of Yosemite National Park in the Sierra Nevada mountain range, and the NASA Airborne Snow Observatory (ASO) lidar‐derived snow data set over 3 years (2013–2015) during a prolonged drought in California, to estimate basin‐scale water balance components. We compare snowmelt and cumulative precipitation over periods from the ASO flight to the end of the water year against cumulative streamflow observations. The basin water balance residual term (snow melt plus precipitation minus streamflow) is calculated for each basin and year. Using soil moisture observations and hydrologic model simulations, we show that the residual term represents short‐term changes in basin water storage over the snowmelt season, but that over the period from peak snow water equivalent (SWE) to the end of summer, it represents cumulative basin‐mean ET. Warm‐season ET estimated from this approach is 168 (85–252 at 95% confidence), 162 (0–326) and 191 (48–334) mm averaged across the basins in 2013, 2014, and 2015, respectively. These values are lower than previous full‐year and point ET estimates in the Sierra Nevada, potentially reflecting reduced ET during drought, the effects of spatial variability, and the part‐year time period. Using streamflow and ASO snow observations, we quantify spatially‐distributed hydrologic processes otherwise difficult to observe.
Flow Resistance Interactions on Hillslopes With Heterogeneous Attributes: Effects on Runoff Hydrograph Characteristics
Authors: Papanicolaou Athanasios N. , Abban Benjamin K. B. , Dermisis Dimitrios C. , Giannopoulos Christos P. , Flanagan Dennis C. , Frankenberger James R. , Wacha Kenneth M.
Published: January 2018

An improved modeling framework for capturing the effects of space and time‐variant resistance to overland flow is developed for intensively managed landscapes. The framework builds on the WEPP model but it removes the limitations of the “equivalent” plane and time‐invariant roughness assumption. The enhanced model therefore accounts for spatiotemporal changes in flow resistance along a hillslope due to changes in roughness, in profile curvature, and downslope variability. The model is used to quantify the degree of influence—from individual soil grains to aggregates, “isolated roughness elements,” and vegetation—on overland flow characteristics under different storm magnitudes, downslope gradients, and profile curvatures. It was found that the net effects of land use change from vegetation to a bare surface resulted in hydrograph peaks that were up to 133% larger. Changes in hillslope profile curvature instead resulted in peak runoff rate changes that were only up to 16%. The stream power concept is utilized to develop a taxonomy that relates the influence of grains, isolated roughness elements, and vegetation, on overland flow under different storm magnitudes and hillslope gradients. Critical storm magnitudes and hillslope gradients were found beyond which the effects of these landscape attributes on the peak stream power were negligible. The results also highlight weaknesses of the space/time‐invariant flow resistance assumption and demonstrate that assumptions on landscape terrain characteristics exert a strong control both on the shape and magnitude of hydrographs, with deviations reaching 65% in the peak runoff when space/time‐variant resistance effects are ignored in some cases.
Three‐Dimensional Effects of Artificial Mixing in a Shallow Drinking‐Water Reservoir
Authors: Chen Shengyang , Little John C. , Carey Cayelan C. , McClure Ryan P. , Lofton Mary E. , Lei Chengwang
Published: January 2018

Studies that examine the effects of artificial mixing for water‐quality mitigation in lakes and reservoirs often view a water column with a one‐dimensional (1‐D) perspective (e.g., homogenized epilimnetic and hypolimnetic layers). Artificial mixing in natural water bodies, however, is inherently three dimensional (3‐D). Using a 3‐D approach experimentally and numerically, the present study visualizes thermal structure and analyzes constituent transport under the influence of artificial mixing in a shallow drinking‐water reservoir. The purpose is to improve the understanding of artificial mixing, which may help to better design and operate mixing systems. In this reservoir, a side‐stream supersaturation (SSS) hypolimnetic oxygenation system and an epilimnetic bubble‐plume mixing (EM) system were concurrently deployed in the deep region. The present study found that, while the mixing induced by the SSS system does not have a distinct 3‐D effect on the thermal structure, epilimnetic mixing by the EM system causes 3‐D heterogeneity. In the experiments, epilimnetic mixing deepened the lower metalimnetic boundary near the diffuser by about 1 m, with 55% reduction of the deepening rate at 120 m upstream of the diffuser. In a tracer study using a 3‐D hydrodynamic model, the operational flow rate of the EM system is found to be an important short‐term driver of constituent transport in the reservoir, whereas the duration of the EM system operation is the dominant long‐term driver. The results suggest that artificial mixing substantially alters both 3‐D thermal structure and constituent transport, and thus needs to be taken into account for reservoir management.
Socio‐Hydrology of Channel Flows in Complex River Basins: Rivers, Canals, and Distributaries in Punjab, Pakistan
Authors: Wescoat James L. , Siddiqi Afreen , Muhammad Abubakr
Published: January 2018

This paper presents a socio‐hydrologic analysis of channel flows in Punjab province of the Indus River basin in Pakistan. The Indus has undergone profound transformations, from large‐scale canal irrigation in the mid‐nineteenth century to partition and development of the international river basin in the mid‐twentieth century, systems modeling in the late‐twentieth century, and new technologies for discharge measurement and data analytics in the early twenty‐first century. We address these processes through a socio‐hydrologic framework that couples historical geographic and analytical methods at three levels of flow in the Punjab. The first level assesses Indus River inflows analysis from its origins in 1922 to the present. The second level shows how river inflows translate into 10‐daily canal command deliveries that vary widely in their conformity with canal entitlements. The third level of analysis shows how new flow measurement technologies raise questions about the performance of established methods of water scheduling (warabandi) on local distributaries. We show how near real‐time measurement sheds light on the efficiency and transparency of surface water management. These local socio‐hydrologic changes have implications in turn for the larger scales of canal and river inflow management in complex river basins.
Large‐Scale Experiments in Microbially Induced Calcite Precipitation (MICP): Reactive Transport Model Development and Prediction
Authors: Nassar Mohamed K. , Gurung Deviyani , Bastani Mehrdad , Ginn Timothy R. , Shafei Babak , Gomez Michael G. , Graddy Charles M. R. , Nelson Doug C. , DeJong Jason T.
Published: January 2018

Design of in situ microbially induced calcite precipitation (MICP) strategies relies on a predictive capability. To date much of the mathematical modeling of MICP has focused on small‐scale experiments and/or one‐dimensional flow in porous media, and successful parameterizations of models in these settings may not pertain to larger scales or to nonuniform, transient flows. Our objective in this article is to report on modeling to test our ability to predict behavior of MICP under controlled conditions in a meter‐scale tank experiment with transient nonuniform transport in a natural soil, using independently determined parameters. Flow in the tank was controlled by three wells, via a complex cycle of injection/withdrawals followed by no‐flow intervals. Different injection solution recipes were used in sequence for transport characterization, biostimulation, cementation, and groundwater rinse phases of the 17 day experiment. Reaction kinetics were calibrated using separate column experiments designed with a similar sequence of phases. This allowed for a parsimonious modeling approach with zero fitting parameters for the tank experiment. These experiments and data were simulated using PHT3‐D, involving transient nonuniform flow, alternating low and high Damköhler reactive transport, and combined equilibrium and kinetically controlled biogeochemical reactions. The assumption that microbes mediating the reaction were exclusively sessile, and with constant activity, in conjunction with the foregoing treatment of the reaction network, provided for efficient and accurate modeling of the entire process leading to nonuniform calcite precipitation. This analysis suggests that under the biostimulation conditions applied here the assumption of steady state sessile biocatalyst suffices to describe the microbially mediated calcite precipitation.
Multiphase Flow Characteristics of Heterogeneous Rocks From CO2 Storage Reservoirs in the United Kingdom
Authors: Reynolds Catriona A. , Blunt Martin J. , Krevor Samuel
Published: January 2018

We have studied the impact of heterogeneity on relative permeability and residual trapping for rock samples from the Bunter sandstone of the UK Southern North Sea, the Ormskirk sandstone of the East Irish Sea, and the Captain sandstone of the UK Northern North Sea. Reservoir condition CO2‐brine relative permeability measurements were made while systematically varying the ratio of viscous to capillary flow potential, across a range of flow rates, fractional flow, and during drainage and imbibition displacement. This variation resulted in observations obtained across a range of core‐scale capillary number
. Capillary pressure heterogeneity was quantitatively inferred from 3‐D observations of the fluid saturation distribution in the rocks. For each of the rock samples, a threshold capillary number,
, was found, below which centimeter‐scale layering resulted in a heterogeneous distribution of the fluid phases and a commensurate impact on flow and trapping. The threshold was found to be dependent on the capillary number alone, irrespective of the displacement path (drainage or imbibition) and average fluid saturation in the rock. The impact of the heterogeneity on the relative permeability varied depending on the characteristics of the heterogeneity in the rock sample, whereas heterogeneity increased residual trapping in all samples above what would be expected from the pore‐scale capillary trapping mechanism alone. Models of subsurface CO2 injection should use properties that incorporate the impacts of heterogeneity at the flow regime of interest or risk significant errors in estimates of fluid flow and trapping.
Investigating Runoff Efficiency in Upper Colorado River Streamflow Over Past Centuries
Authors: Woodhouse Connie A. , Pederson Gregory T.
Published: January 2018

With increasing concerns about the impact of warming temperatures on water resources, more attention is being paid to the relationship between runoff and precipitation, or runoff efficiency. Temperature is a key influence on Colorado River runoff efficiency, and warming temperatures are projected to reduce runoff efficiency. Here, we investigate the nature of runoff efficiency in the upper Colorado River (UCRB) basin over the past 400 years, with a specific focus on major droughts and pluvials, and to contextualize the instrumental period. We first verify the feasibility of reconstructing runoff efficiency from tree‐ring data. The reconstruction is then used to evaluate variability in runoff efficiency over periods of high and low flow, and its correspondence to a reconstruction of late runoff season UCRB temperature variability. Results indicate that runoff efficiency has played a consistent role in modulating the relationship between precipitation and streamflow over past centuries, and that temperature has likely been the key control. While negative runoff efficiency is most common during dry periods, and positive runoff efficiency during wet years, there are some instances of positive runoff efficiency moderating the impact of precipitation deficits on streamflow. Compared to past centuries, the 20th century has experienced twice as many high flow years with negative runoff efficiency, likely due to warm temperatures. These results suggest warming temperatures will continue to reduce runoff efficiency in wet or dry years, and that future flows will be less than anticipated from precipitation due to warming temperatures.
Modeling Bimolecular Reactive Transport With Mixing‐Limitation: Theory and Application to Column Experiments
Authors: Ginn T. R.
Published: January 2018

The challenge of determining mixing extent of solutions undergoing advective‐dispersive‐diffusive transport is well known. In particular, reaction extent between displacing and displaced solutes depends on mixing at the pore scale, that is, generally smaller than continuum scale quantification that relies on dispersive fluxes. Here a novel mobile‐mobile mass transfer approach is developed to distinguish diffusive mixing from dispersive spreading in one‐dimensional transport involving small‐scale velocity variations with some correlation, such as occurs in hydrodynamic dispersion, in which short‐range ballistic transports give rise to dispersed but not mixed segregation zones, termed here ballisticules. When considering transport of a single solution, this approach distinguishes self‐diffusive mixing from spreading, and in the case of displacement of one solution by another, each containing a participant reactant of an irreversible bimolecular reaction, this results in time‐delayed diffusive mixing of reactants. The approach generates models for both kinetically controlled and equilibrium irreversible reaction cases, while honoring independently measured reaction rates and dispersivities. The mathematical solution for the equilibrium case is a simple analytical expression. The approach is applied to published experimental data on bimolecular reactions for homogeneous porous media under postasymptotic dispersive conditions with good results.
Training‐Image Based Geostatistical Inversion Using a Spatial Generative Adversarial Neural Network
Authors: Laloy Eric , Hérault Romain , Jacques Diederik , Linde Niklas
Published: January 2018

Probabilistic inversion within a multiple‐point statistics framework is often computationally prohibitive for high‐dimensional problems. To partly address this, we introduce and evaluate a new training‐image based inversion approach for complex geologic media. Our approach relies on a deep neural network of the generative adversarial network (GAN) type. After training using a training image (TI), our proposed spatial GAN (SGAN) can quickly generate 2‐D and 3‐D unconditional realizations. A key characteristic of our SGAN is that it defines a (very) low‐dimensional parameterization, thereby allowing for efficient probabilistic inversion using state‐of‐the‐art Markov chain Monte Carlo (MCMC) methods. In addition, available direct conditioning data can be incorporated within the inversion. Several 2‐D and 3‐D categorical TIs are first used to analyze the performance of our SGAN for unconditional geostatistical simulation. Training our deep network can take several hours. After training, realizations containing a few millions of pixels/voxels can be produced in a matter of seconds. This makes it especially useful for simulating many thousands of realizations (e.g., for MCMC inversion) as the relative cost of the training per realization diminishes with the considered number of realizations. Synthetic inversion case studies involving 2‐D steady state flow and 3‐D transient hydraulic tomography with and without direct conditioning data are used to illustrate the effectiveness of our proposed SGAN‐based inversion. For the 2‐D case, the inversion rapidly explores the posterior model distribution. For the 3‐D case, the inversion recovers model realizations that fit the data close to the target level and visually resemble the true model well.
Study on estimation of compressive strength of concrete in structure using ultrasonic method
Authors: Watanabe Satoshi , Hishikawa Kazumi , Kamae Kengo , Namiki Satoru
Published: January 2018

In this study, for improving the accuracy of estimating the compressive strength of concrete using the ultrasonic method, a method for measuring the ultrasonic velocity and a method for estimating the strength of concrete were investigated. In an experiment with reinforced concrete members of actual size, the precision of the proposed method for measuring the ultrasonic velocity of inner concrete was confirmed to be high. Furthermore, the estimated value of the compressive strength of concrete in structure using the proposed strength estimation method was close to the actual measurement value.
Development of a building continuity support system as building management system for business continuity—Fundamental research on implementation of resilient buildings
Authors: Masuda Yukihiro
Published: January 2018

The resilience of buildings can be improved by revising the methods of building management. This paper discusses the development of a new building management system for continuity of important operations. In the early stages after a disaster, it is important to assess what happened, the actual conditions, whether important operation spaces can be used, the causes of malfunctions, and what should be done to achieve continuity or early restoration of functions. This report presents a methodology to support the process of systematically confirming the actual conditions, judgment, adjustment, and actions for the building manager.
Modeling of interactions between RC columns and masonry infill in buildings with a column‐sway mechanism
Authors: Sanada Yasushi , Maidiawati
Published: January 2018

This study proposes a new analytical model to evaluate interactions between reinforced concrete (RC) columns and masonry infill. An infill is replaced by a diagonal strut and its width is defined by column/infill contact length. A calculation procedure is presented to determine the contact length by mainly considering compression balance and lateral displacement compatibility at the column/infill interface. The proposed model is verified by performing a comparison with an experiment on a concrete block infilled RC frame in which the column/infill interactions are observed in detail. The model effectively evaluates both the strength of the infilled frame and its deformability.
Brain atrophy measures in preclinical and manifest spinocerebellar ataxia type 2
Authors: Reetz Kathrin , Rodríguez‐Labrada Roberto , Dogan Imis , Mirzazade Shahram , Romanzetti Sandro , Schulz Jörg B. , Cruz‐Rivas Edilia M. , Alvarez‐Cuesta Jose A. , Aguilera Rodríguez Raul , Gonzalez Zaldivar Yanetza , Auburger Georg , Velázquez‐Pérez Luis
Published: January 2018

Objective

Spinocerebellar ataxia type 2 (SCA2) is an autosomal dominantly inherited neurodegenerative disease mainly affecting the cerebellum and brainstem. In this Cuban‐German research collaboration, we aimed to characterize atrophy patterns and associations with clinical measures in preclinical and manifest SCA2.

Methods

In this study, 16 nonmanifest SCA2 mutation carriers, 26 manifest patients with SCA2, and 18 healthy control subjects underwent magnetic resonance imaging, as well as genetic and clinical characterization including assessment of ataxia (Scale for the Assessment and Rating of Ataxia) and saccade velocity in Cuba were enrolled. Semiautomated quantitative volumetry of the cerebellum and brainstem, subdivided into the medulla oblongata, the pontine brainstem, and mesencephalon was performed. Additionally, the anteroposterior diameter of the pontine brainstem was measured.

Results

Analysis of volumetric data revealed degeneration of the cerebellum and brainstem, in particular of pontine volumes and the anteroposterior diameter of the pons, in both manifest SCA2 patients and individuals at risk for SCA2 compared to controls. Comparing patients with nonataxic preclinical SCA2 mutation carriers, we found more pronounced reductions of the pontine brainstem and cerebellum in manifest SCA2. Volumetric data further showed associations with CAG repeat length and predicted age of onset in preclinical SCA2 individuals, and by trend with ataxia signs in patients. Although saccade velocity was associated with reduction in the pontine brainstem in preclinical and manifest SCA2, reduced ability to suppress interfering stimuli measured by the Stroop task was related to cerebellar volume loss in patients.

Interpretation

Preclinical SCA2 mutation carriers exhibit brain abnormalities, which could be targeted as surrogate parameters for disease progression and in future preventive trials.
Medical Care Costs Associated With Rheumatoid Arthritis in the US: A Systematic Literature Review and Meta‐Analysis
Authors: Hresko Andrew , Lin Tzu‐Chieh , Solomon Daniel H.
Published: January 2018

Objective

Rheumatoid arthritis (RA) is a morbid, mortal, and costly condition without a cure. Treatments for RA have expanded over the last 2 decades, and direct medical costs may differ by types of treatments. There has not been a systematic literature review since the introduction of new RA treatments, including biologic disease‐modifying antirheumatic drugs (bDMARDs).

Methods

We conducted a systematic literature review with meta‐analysis of direct medical costs associated with RA patients cared for in the US since the marketing of the first bDMARD. Standard search strategies and sources were used, and data were extracted independently by 2 reviewers. The methods and quality of included studies were assessed. Total direct medical costs as well as RA‐specific costs were calculated using random‐effects meta‐analysis. Subgroups of interest included Medicare patients and those using bDMARDs.

Results

We found 541 potentially relevant studies, and 12 articles met the selection criteria. The quality of studies varied: one‐third were poor, one‐third were fair, and one‐third were good. Total direct medical costs were estimated at $12,509 (95% confidence interval [95% CI] 7,451–21,001) for all RA patients using any treatment regimen and $36,053 (95% CI 32,138–40,445) for bDMARD users. RA‐specific costs were $3,723 (95% CI 2,408–5,762) for all RA patients using any treatment regimen and $20,262 (95% CI 17,480–23,487) for bDMARD users.

Conclusion

The total and disease‐specific direct medical costs for patients with RA is substantial. Among bDMARD users, the cost of RA care is more than half of all direct medical costs.