bluuebunny/crossref_metadata_2025_split huggingface dataset:
Prediction of vegetation anomalies to improve food security and water management in India
Authors: Asoka Akarsh , Mishra Vimal 
Published: June 2015

AbstractPrediction of vegetation anomalies at regional scales is essential for management of food and water resources. Forecast of vegetation anomalies at 1–3 months lead time can help in decision making. Here we show that normalized difference vegetation index (NDVI) along with other hydroclimatic variables (soil moisture and sea surface temperature) can be effectively used to predict vegetation anomalies in India. The spatiotemporal analysis of NDVI showed significant greening over the region during the period of 1982–2013. The root‐zone soil moisture showed a positive correlation with NDVI, whereas the El Niño–Southern Oscillation index (Nino 3.4) is negatively correlated in most of the regions. We extended this relationship to develop a model to predict NDVI in 1 to 3 months lead time. The predicted vegetation anomalies compare well with observations, which can be effectively utilized in early warning and better planning in water resources and agricultural sectors in India.
Fluid‐faulting interactions: Fracture‐mesh and fault‐valve behavior in the February 2014 Mammoth Mountain, California, earthquake swarm
Authors: Shelly David R. , Taira Taka'aki , Prejean Stephanie G. , Hill David P. , Dreger Douglas S. 
Published: June 2015

AbstractFaulting and fluid transport in the subsurface are highly coupled processes, which may manifest seismically as earthquake swarms. A swarm in February 2014 beneath densely monitored Mammoth Mountain, California, provides an opportunity to witness these interactions in high resolution. Toward this goal, we employ massive waveform‐correlation‐based event detection and relative relocation, which quadruples the swarm catalog to more than 6000 earthquakes and produces high‐precision locations even for very small events. The swarm's main seismic zone forms a distributed fracture mesh, with individual faults activated in short earthquake bursts. The largest event of the sequence,M3.1, apparently acted as a fault valve and was followed by a distinct wave of earthquakes propagating ~1 km westward from the updip edge of rupture, 1–2 h later. Late in the swarm, multiple small, shallower subsidiary faults activated with pronounced hypocenter migration, suggesting that a broader fluid pressure pulse propagated through the subsurface.
Significant modulation of variability and projected change in California winter precipitation by extratropical cyclone activity
Authors: Chang Edmund K. M. , Zheng Cheng , Lanigan Patrick , Yau Albert M. W. , Neelin J. David 
Published: June 2015

AbstractExtratropical cyclones give rise to much of the precipitation over California. Observed California winter precipitation is highly correlated to a metric of extratropical cyclone activity over the Eastern Pacific. The lack of precipitation over the recent winters is coincident with consecutive winters of much below average cyclone activity. Analysis of variability in cyclone activity and California precipitation simulated by models participating in Coupled Model Intercomparison Project Phase 5 indicates that most models can simulate the relationship between cyclone activity and precipitation well. Examination of projected change suggests (1) no evidence of a long‐term downward trend in California region cyclone activity within the examined scenarios and (2) that the intermodel spread in California precipitation projection can be largely explained by the spread in the projection of extratropical cyclone activity. This highlights the need to further understand physical mechanisms for the variation in projection of cyclone activity in this region.
The seasonal cycle of the Arctic Ocean under climate change
Authors: Carton James A. , Ding Yanni , Arrigo Kevin R. 
Published: June 2015

AbstractThe seasonal cycle of Arctic Ocean temperature is weak due to the insulating and light‐scattering effects of sea ice cover and the moderating influence of the seasonal storage and release of heat through ice melting and freezing. The retreat of sea ice and other changes in recent decades is already warming surface air temperatures in winter. These meteorological changes raise the question of how the seasonal cycle of the ocean may change. Here we present results from coupled climate model simulations showing that the loss of sea ice will dramatically increase the amplitude of the seasonal cycle of sea surface temperature in the Arctic Ocean. Depending on the rate of growth of atmospheric greenhouse gases, the seasonal range in Arctic sea surface temperature may exceed 10°C by year 2300, greatly increasing the stratification of the summer mixed layer.
Effect of local variability in erosional resistance on large‐scale morphodynamic response of salt marshes to wind waves and extreme events
Authors: Leonardi Nicoletta , Fagherazzi Sergio 
Published: June 2015

AbstractWe use field data and a cellular automata model to investigate salt marsh response to wave action under different wave energy conditions and frequency of extreme events. Our results suggest that salt marsh response to wind waves is tied to their local properties. In case of low‐wave‐energy conditions, local variability in marsh resistance might lead to the unpredictable failure of large marsh portions with respect to average erosion rates. High‐wave‐energy conditions, while overall leading to faster marsh deterioration, produce constant and predictable erosion rates. A high occurrence of extreme events leads to smoother and more uniformly deteriorating marsh boundary profiles. Salt marshes subject to weak wave energy conditions are the most susceptible to variations in the frequency of extreme events. This suggests that variations in time in the morphology of salt marsh boundaries could be used to infer changes in frequency and magnitude of external agents.
The impact of sea surface temperature bias on equatorial Atlantic interannual variability in partially coupled model experiments
Authors: Ding Hui , Greatbatch Richard J. , Latif Mojib , Park Wonsun 
Published: June 2015

AbstractWe examine the impact of sea surface temperature (SST) bias on interannual variability during boreal summer over the equatorial Atlantic using two suites of partially coupled model (PCM) experiments with and without surface heat flux correction. In the experiments, surface wind stress anomalies are specified from observations while the thermodynamic coupling between the atmospheric and oceanic components is still active as in the fully coupled model. The results show that the PCM can capture around 50% of the observed variability associated with the Atlantic Niño from 1958 to 2013, but only when the bias is substantially reduced using heat flux correction, with no skill otherwise. We further show that ocean dynamics explain a large part of the SST variability in the eastern equatorial Atlantic in both observations (50–60%) and the PCM experiments (50–70%) with heat flux correction, implying that the seasonal predictability potential may be higher than currently thought.
Thermospheric poleward wind surge at midlatitudes during great storm intervals
Authors: Zhang Shun‐Rong , Erickson Philip J. , Foster John C. , Holt John M. , Coster Anthea J. , Makela Jonathan J. , Noto John , Meriwether John W. , Harding Brian J. , Riccobono Juanita , Kerr Robert B. 
Published: June 2015

AbstractWe report a significant poleward surge in thermospheric winds at subauroral and midlatitudes following the 17–18 March 2015 great geomagnetic storm. This premidnight surge is preceded by strong westward winds. These disturbances were observed over three sites with geodetic latitudes 35–42°N in the American sector by Fabry‐Perot interferometers at 630 nm wavelength. Prior to the wind disturbances, subauroral polarization streams (SAPS) were measured by the Millstone Hill incoherent scatter radar between 20 and 02 UT. We identify the observed neutral wind variations as driven by SAPS, through a scenario where strong ion flows cause a westward neutral wind, subsequently establishing a poleward wind surge due to the poleward Coriolis force on that westward wind. These regional disturbances appear to have prevented the well‐known storm time equatorward wind surge from propagating into low latitudes, with the consequence that the classic disturbance dynamo mechanism failed to occur.
A case study of electron precipitation fluxes due to plasmaspheric hiss
Authors: Hardman Rachael , Clilverd Mark A. , Rodger Craig J. , Brundell James B. , Duthie Roger , Holzworth Robert H. , Mann Ian R. , Milling David K. , Macusova Eva 
Published: June 2015

AbstractWe find that during a large geomagnetic storm in October 2011 the trapped fluxes of >30, >100, and >300 keV outer radiation belt electrons were enhanced at L = 3–4 during the storm main phase. A gradual decay of the trapped fluxes was observed over the following 5–7 days, even though no significant precipitation fluxes could be observed in the Polar Orbiting Environmental Satellite (POES) electron precipitation detectors. We use the Antarctic‐Arctic Radiation‐belt (Dynamic) Deposition–VLF Atmospheric Research Konsortium receiver network to investigate the characteristics of the electron precipitation throughout the storm period. Weak electron precipitation was observed on the dayside for 5–7 days, consistent with being driven by plasmaspheric hiss. Using a previously published plasmaspheric hiss‐induced electron energy e‐folding spectrum of E0 = 365 keV, the observed radio wave perturbation levels at L = 3–4 were found to be caused by >30 keV electron precipitation with flux ~100 el cm−2 s−1 sr−1. The low levels of precipitation explain the lack of response of the POES telescopes to the flux, because of the effect of the POES lower sensitivity limit and ability to measure weak diffusion‐driven precipitation. The detection of dayside, inner plasmasphere electron precipitation during the recovery phase of the storm is consistent with plasmaspheric hiss wave‐particle interactions and shows that the waves can be a significant influence on the evolution of the outer radiation belt trapped flux that resides inside the plasmapause.
Do eddies ride on Rossby waves?
Authors: Polito Paulo S. , Sato Olga T. 
Published: June 2015

AbstractBoth vortices and baroclinic Rossby waves show up as westward‐propagating features in the sea surface height anomaly (SSHA) records when displayed in the form of zonal‐temporal or Hovmöller diagrams. A chain of filters was used to separate the SSHA into orthogonal components. Each of the filtered components was then reassembled as a set of maps. In the maps of individual components, we clearly see westward propagating Rossby waves. Our most striking findings are: (i) limited within their critical latitudes, the wave extrema coincide with a significant number of vortices; (ii) eddy‐wave coincidence occurs at a preferred latitude that depends on the wave period; (iii) among the vortices that, at some point of their existence coincide with a wave, a relatively large percentage of them remained their whole lifetime with the wave, and (iv) a mechanism is proposed to explain why eddies tend to remain over the wave extrema (crests and troughs). Our answer to the title question is: yes, they often do.
Anisotropic internal thermal stress in sea ice from the Canadian Arctic Archipelago
Authors: Hata Y. , Tremblay L. B. 
Published: June 2015

AbstractResults from an ice stress buoy deployed near the center of a multi‐year floe in the Viscount Melville Sound of the Canadian Arctic Archipelago between 10 October 2010 and 17 August 2011 are presented. The position record indicates the landlocked season was approximately 5 months, from 18 January to 22 June, when the sea ice was fast to Melville Island and Victoria Island. Thermal stresses (ranging from −84 to 66 kPa) dominate the internal stress record, with only a few dynamic stress events (∼50 kPa) recorded before the landlocked season. Intriguingly, the thermal stresses are isotropic before the landlocked ice onset and anisotropic during the landlocked season. Two possible causes to explain anisotropy in thermal stresses are considered: preferred c axis alignment of the ice crystal, and land confinement associated with the nearby coastline. The orientation of the principal stresses indicates that land confinement is responsible for the anisotropy. The stress record also clearly shows the presence of residual compressive stresses at the melt onset, suggesting a viscous creep relaxation time constant of several days. Finally, results show an interesting reversal in the sign of the correlation (from negative to positive) between surface air temperature and thermal stress after the onset of surface melt. We attribute this to the onset of water infiltration within sea ice after which colder night temperature leads to refreezing and compressive stresses. To the best of the authors' knowledge, this is the first time that anisotropic thermal stresses have been reported in sea ice.
Environmental controls of marine productivity hot spots around Antarctica
Authors: Arrigo Kevin R. , van Dijken Gert L. , Strong Aaron L. 
Published: June 2015

AbstractAntarctic coastal polynyas are biologically rich ecosystems that support large populations of mammals and birds and are globally significant sinks of atmospheric carbon dioxide. To support local phytoplankton blooms, these highly productive ecosystems require a large input of iron (Fe), the sources of which are poorly known. Here we assess the relative importance of six different environmental factors in controlling the amount of phytoplankton biomass and rates of net primary production (NPP) in 46 coastal polynyas around Antarctica. Data presented here suggest that melting ice shelves are a primary supplier of Fe to coastal polynyas, with basal melt rates explaining 59% of the between‐polynya variance in mean chlorophyll a (Chl a) concentration. In a multiple regression analysis, which explained 78% of the variance in chlorophyll a (Chl a) between polynyas, basal melt rate explained twice as much of the variance as the next most important variable. Fe upwelled from sediments, which is partly controlled by continental shelf width, was also important in some polynyas. Of secondary importance to phytoplankton abundance and NPP were sea surface temperature and polynya size. Surprisingly, differences in light availability and the length of the open water season explained little or none of the variance in either Chl a or NPP between polynyas. If the productivity of coastal polynyas is indeed sensitive to the release of Fe from melting ice shelves, future changes in ice shelf melt rates could dramatically influence Antarctic coastal ecosystems and the ability of continental shelf waters to sequester atmospheric carbon dioxide.
When does the lightning attachment process actually begin?
Authors: Tran M. D. , Rakov V. A. 
Published: June 2015

AbstractHigh‐speed video and electric field records of 43 first and 7 new‐ground‐termination subsequent strokes in negative lightning flashes, obtained at the Lightning Observatory in Gainesville, Florida, were examined. Eighteen (36%) of these strokes exhibited faintly luminous formations (FLFs) below the downward leader tip just prior to the return stroke. All the 18 FLFs were connected to the strike object on the ground, with 14 of them being also in contact with the downward leader tip. For 11 located events showing FLFs in contact with the downward leader tip, the FLF 2‐D length ranged from 51 to 200 m and the time interval between the end of exposure of the FLF frame and the return stroke onset ranged from 42 to 106 μs. We inferred that the FLFs mostly consisted of relatively low conductivity streamers, based on the following observations and estimates. (a) The rates at which the 11 FLFs were replaced by channels capable of guiding return stroke waves ranged from 0.7 × 106 m/s to 2.2 × 106 m/s, which is comparable to leader speeds in virgin air (in the same records). (b) The overwhelming majority of downward leaders continued stepping while being connected to ground via FLFs. (c) The average electric field along FLFs is 1 to 2 orders of magnitude higher than expected for hot, leader‐like channels. Since in all cases the FLF determined the strike point, we conclude that its inferred initiation up to a few hundreds of microseconds before the return stroke onset signified the beginning of the lightning attachment process.
Ventilation time scales of the North Atlantic subtropical cell revealed by coral radiocarbon from the Cape Verde Islands
Authors: Fernandez Alvaro , Lapen Thomas J. , Andreasen Rasmus , Swart Peter K. , White Christopher D. , Rosenheim Brad E. 
Published: June 2015

AbstractWe present coral‐ and sclerosponge‐based reconstructions of the 14C content in North Atlantic dissolved inorganic carbon (DIC) during the last ~100 years from the subtropical cells (STCs). These waters are sensitive to the dynamics of the shallow overturning meridional circulation that transports heat and water masses from the subtropics to the tropics. We use these records to investigate the circulation patterns of the off‐equatorial upwelling regions of the STCs, which are not well understood. Coral and sclerosponge skeletons provide long time series of ocean DIC 14C content, a tracer of oceanic circulation, effectively extending the observational record back in time. Sclerosponge data from the Bahamas were used to extend the existing subtropical 14C time series to the 21st century. Coral 14C data from the Cape Verde Islands (1890–2002) captured the 14C signature of water brought to the surface in the off‐equatorial regions of the STC present near the West African coast. We observe a unique postbomb trend at Cape Verde that is similar to the upwelling regions in the Pacific, and we interpret this trend as the result of the slow penetration of bomb 14C into the interior ocean as part of the STC circulation. Using a multibox mixing model we constrain the time history of bomb 14C in the eastern tropical Atlantic, and we estimate a 20 year time scale for ventilation of the thermocline in this area of the ocean. The similarity between the Atlantic and Pacific 14C‐based records of upwelling suggests that both are caused by bomb 14C penetration rather than more complex explanations that invoke changes in thermocline depth (e.g., related to El Niño–Southern Oscillation variability) or changes in the strength of the subtropical cells. Our results offer constraints for models of tropical ocean circulation and anthropogenic CO2 uptake that attempt to reproduce the characteristics of the shallow wind‐driven circulation in the Atlantic.
Suppressed convective rainfall by agricultural expansion in southeastern Burkina Faso
Authors: Mande Theophile , Ceperley Natalie C. , Katul Gabriel G. , Tyler Scott W. , Yacouba Hamma , Parlange Marc B. 
Published: June 2015

AbstractWith the “green economy” being promoted as a path to sustainable development and food security within the African continent, the influx of agricultural land is proliferating at a rapid pace often replacing natural savannah forests. Where agriculture is primarily rainfed, the possible adverse impacts of agricultural land influx on rainfall occurrences in water‐limited areas such as West Africa warrant attention. Using field observations complemented by model calculations in southeastern Burkina Faso, the main causes of a 10–30% suppressed daytime rainfall recorded over agricultural fields when referenced to natural savannah forests are examined. Measurements and model runs reveal that the crossing of the mixed layer height and lifting condensation levels, a necessary condition for cloud formation and subsequent rainfall occurrence, was 30% more frequent above the natural savannah forest. This increase in crossing statistics was primarily explained by increases in measured sensible heat flux above the savannah forest rather than differences in lifting condensation heights.
Medication Nonadherence Is Associated With Increased Subsequent Acute Care Utilization Among Medicaid Beneficiaries With Systemic Lupus Erythematosus
Authors: Feldman Candace H. , Yazdany Jinoos , Guan Hongshu , Solomon Daniel H. , Costenbader Karen H. 
Published: June 2015

ObjectiveWe examined whether nonadherence to hydroxychloroquine (HCQ) or immunosuppressive medications (ISMs) was associated with higher subsequent acute care utilization among Medicaid beneficiaries with systemic lupus erythematosus (SLE).MethodsWe utilized US Medicaid data from 2000–2006 to identify adults ages 18–64 years with SLE who were new users of HCQ or ISMs. We defined the index date as receipt of HCQ or ISMs without use in the prior 6 months. We measured adherence using the medication possession ratio (MPR), the proportion of days covered by total days’ supply dispensed, for the 1‐year post‐index date. Our outcomes were all‐cause and SLE‐related emergency department (ED) visits and hospitalizations in the subsequent year. We used multivariable Poisson regression models to examine the association between nonadherence (MPR <80%) and acute care utilization, adjusting for sociodemographics and comorbidities.ResultsWe identified 9,600 HCQ new users and 3,829 ISM new users with SLE. The mean ± SD MPR for HCQ was 47.8% ± 30.3% and for ISMs was 42.7% ± 30.7%. Seventy‐nine percent of HCQ users and 83% of ISM users were nonadherent (MPR <80%). In multivariable models, among HCQ users, the incidence rate ratio (IRR) of ED visits was 1.55 (95% confidence interval [95% CI] 1.43–1.69) and the IRR of hospitalizations was 1.37 (95% CI 1.25–1.50), comparing nonadherers to adherers. For ISM users, the IRR of ED visits was 1.64 (95% CI 1.42–1.89) and of hospitalizations was 1.67 (95% CI 1.41–1.96) for nonadherers versus adherers.ConclusionIn this cohort, nonadherence to HCQ and ISMs was common and was associated with significantly higher subsequent acute care utilization.
Etanercept‐Methotrexate Combination Therapy Initiators Have Greater Adherence and Persistence Than Triple Therapy Initiators With Rheumatoid Arthritis
Authors: Bonafede Machaon , Johnson Barbara H. , Tang Derek H. , Shah Neel , Harrison David J. , Collier David H. 
Published: June 2015

ObjectiveTo estimate adherence and persistence with etanercept plus methotrexate (ETN‐MTX) combination therapy and MTX, hydroxychloroquine, and sulfasalazine triple therapy at 1 year following treatment initiation in adults with rheumatoid arthritis (RA).MethodsThis retrospective analysis used data from the Truven Health MarketScan Commercial and Medicare Supplemental databases from January 2009 to July 2013. Adherence was defined as having percentage of days covered >80% for all drugs within each regimen. Persistence was defined as no treatment gap >45 days for any drug and no addition or switching to other disease‐modifying antirheumatic drugs. Multiple logistic regression models were employed in the analyses to control for potential confounders.ResultsA total of 3,724 ETN‐MTX patients and 818 triple therapy patients were eligible. At 1 year, 27.9% who were taking ETN‐MTX and 18.2% using triple therapy were adherent to all agents in their regimen (P < 0.0001), and 29.4% who were taking ETN‐MTX and 23.2% using triple therapy were persistent (P < 0.001). After adjusting for confounders, ETN‐MTX patients had significantly greater odds of being adherent (odds ratio [OR] 1.79, 95% confidence interval [95% CI] 1.47–2.17) and persistent (OR 1.45, 95% CI 1.20–1.72) compared with patients using triple therapy.ConclusionPatients with RA initiating treatment with ETN‐MTX combination therapy demonstrated greater adherence and persistence at 1 year than patients initiating triple therapy.