bluuebunny/crossref_metadata_2025_split huggingface dataset:
Heavy Ion Composition of Mercury's Magnetosphere
Authors: Wurz P. , Gamborino D. , Vorburger A. , Raines J. M. 
Published: April 2019

AbstractWe modeled the exospheric densities for sputtering and thermal desorption in detail for the time period of the first MESSENGER flyby of Mercury. From the exospheric densities we calculate ion production rates. These ions will be transported to the location of MESSENGER if they are produced on magnetic field lines connecting the cusp with the downwind side. From these ions we produce mass spectra that we compared with the Fast Imaging Plasma Spectrometer measurements performed during this flyby. We find good qualitative agreement between the modeled and the measured ion mass spectrum. We find that sputtering is a major process to contribute to the population of planetary ions in the magnetosphere because of the large scale height of the exospheric particles and the resulting long flight times. In addition, thermal desorption of Na contributes significant amounts to the magnetospheric ion population. From the volatile species we can identify He, OH, H2O, and Ne in the measured mass spectrum. However, for most of the volatile species the reported upper limits must be reduced by 2–3 orders of magnitude to be compatible to the measured ion spectrum.
Evaporative Implications of Dry‐Air Outbreaks Over the Northern Red Sea
Authors: Menezes Viviane V. , Farrar J. Thomas , Bower Amy S. 
Published: April 2019

AbstractWe investigate the impacts of westward wind events on the Red Sea evaporation using the 35‐year second Modern‐Era Retrospective analysis for Research and Applications reanalysis and a 2‐year‐long record of in situ observations from a heavily instrumented air‐sea interaction mooring. These events are common during boreal winter, and their effects are similar to cold‐air outbreaks that occur in midpolar and subpolar latitudes. They cause extreme heat loss from the sea, which is dominated by latent heat fluxes. Different from cold‐air outbreaks, the intensified heat loss is due to the low relative humidity as we show through latent heat flux decomposition. Rainfall is negligible during these events, and we refer to them as dry‐air outbreaks. We also investigate the general atmospheric circulation pattern that favors their occurrence, which is associated with an intensified Arabian High at the north‐central portion of the Arabian Peninsula—a feature that seems to be an extension of the Siberian High. The analyses reveal that the westward winds over the northern Red Sea and the winter Shamal winds in the Persian Gulf are very likely to be part of the same subsynoptic‐scale feature. The second Modern‐Era Retrospective analysis for Research and Applications reanalysis indicates that the occurrence of westward wind events over the northern Red Sea has grown from 1980 to 2015, especially the frequency of large‐scale events, the cause of which is to be investigated. We hypothesize that dry‐air outbreaks may induce surface water mass transformation in the surface Red Sea Eastern Boundary Current and could represent a significant process for the oceanic thermohaline‐driven overturning circulation.
Wintertime Boundary Layer Evolution and Air Pollution Potential Over the Kathmandu Valley, Nepal
Authors: Regmi Ram P. , Kitada Toshihiro , Maharjan Sangeeta , Shrestha Sajan , Shrestha Saraswati , Regmi Greema 
Published: April 2019

AbstractMeteorological effects on wintertime air pollution in the Kathmandu Valley were investigated using SOnic Detection and Ranging soundings, Automatic Weather Station measurements, numerical simulation using Weather Research and Forecasting data, and Chemical Transport Modeling during February 2013. A surrogate for black carbon was used for transport simulation in order to better understand the effects of local meteorological factors on air pollution. In the simulation, the emission strength of the black carbon surrogate was assumed temporally constant and spatially uniform over the Kathmandu Valley floor. The Weather Research and Forecasting simulation results were well correlated with observed meteorological measurements and demonstrated diurnal periodicity such as intrusion of westerly‐northwesterly wind into the Kathmandu Valley and modification of the boundary layer activity due to afternoon wind. The transport simulation suggested long‐lasting weak wind, thermally stable stratification, and associated small turbulence during the night and morning caused potentially severe air pollution. We propose a method using wind velocity and turbulent kinetic energy in the surface layer to characterize pollution level in the Kathmandu Valley.
Multiobjective Calibration of a Global Biogeochemical Ocean Model Against Nutrients, Oxygen, and Oxygen Minimum Zones
Authors: Sauerland Volkmar , Kriest Iris , Oschlies Andreas , Srivastav Anand 
Published: April 2019

AbstractGlobal biogeochemical ocean models rely on many parameters, which govern the interaction between individual components, and their response to the physical environment. They are often assessed/calibrated against quasi‐synoptic data sets of dissolved inorganic tracers. However, a good fit to one observation might not necessarily imply a good match to another. We investigate whether two different metrics—the root‐mean‐square error to nutrients and oxygen and a metric measuring the overlap between simulated and observed oxygen minimum zones (OMZs)—help to constrain a global biogeochemical model in different aspects of performance. Three global model optimizations are carried out. Two single‐objective optimizations target the root‐mean‐square metric and a sum of both metrics, respectively. We then present and explore multiobjective optimization, which results in a set of compromise solutions. Our results suggest that optimal parameters for denitrification and nitrogen fixation differ when applying different metrics. Optimization against observed OMZs leads to parameters that enhance fixed nitrogen cycling; this causes too low nitrate concentrations and a too high global pelagic denitrification rate. Optimization against nutrient and oxygen concentrations leads to different parameters and a lower global fixed nitrogen turnover; this results in a worse fit to OMZs. Multiobjective optimization resolves this antagonistic effect and provides an ensemble of parameter sets, which help to address different research questions. We finally discuss how systematic model calibration can help to improve models used for projecting climate change and its effect on fisheries and climate gas emissions.
Generalized Additive Modeling Combined With Multiple Collinear for ICME Velocity Forecasting
Authors: Lu J. Y. , Jin C. Q. , Wang M. , Ji H. S. , Iluore K. , Guan H. Y. , Li J. F. , Li J. Y. 
Published: April 2019

AbstractOne of the main issues of space weather is the timely prediction of disturbed solar wind parameters at L1, especially caused by Coronal Mass Ejection (CME). Using the data from 170 front halo, flare‐associated CMEs, and in‐site solar wind data, an analysis of the Interplanetary Coronal Mass Ejection (ICME) peak velocity at L1 related to associated coronal parameters is performed. The statistical methods including the Generalized Additive Modeling (GAM) and Multiple Collinear (MC) have been applied to explain the underlying physical reasons and set up a new prediction model. Our results indicate that (1) X‐flare integral flux, CME linear velocity, and Acceleration observed on corona play key roles in ICME velocity, while other coronal parameters only present a weak correlation, such as the CME Mass and Angular Width, (2) the relationship between ICME velocity and CME Acceleration, as well as CME linear velocity, is nonstationary, and the ICME velocity will increase with the increasing CME Acceleration or linear velocity until saturation, and (3) MC is an effective method to improve the forecast model performance. Compared with 0.52 for only GAM, the correlation coefficient using GAM + MC reaches to 0.71. To further testify the prediction ability, the GAM + MC model results are compared with the Back‐Propagation network model and a typically empirical statistic relation proposed by Manoharan (2006, https://doi.org/10.1007/s11207-006-0100-y; their correlation coefficients and root mean squared errors are both roughly 0.6 and 100 km/s, respectively). It is found that the MC + GAM can upgrade the forecast at least over 10%.
An Approach to Tracking Meteorological Drought Migration
Authors: Zhou Han , Liu Yuanbo , Liu Yongwei 
Published: April 2019

AbstractSpatiotemporal behaviors of meteorological droughts are basic for understanding the development and driving forces of droughts. Currently, there are a limited number of approaches mainly used to analyze the spatiotemporal evolution of large‐scale soil moisture/hydrological drought events at global or continental scales. These behavior description approaches on the spatiotemporal dynamics of drought are not perfect and should be improved further. To this end, a new approach was proposed to investigate the migration of meteorological droughts based on topological spatial relations. It was used to identify drought clusters, migration trajectories, and migration directions of meteorological droughts. In the Poyang Lake basin (24°29′ to 30°04′N, 113°34′ to 118°28′E), China, monthly precipitation data were available from 1960 to 2007. The one‐month standardized precipitation index was used to characterize meteorological droughts. The proposed approach identified a total of 77 drought events and 454 drought clusters during the study period. Their drought centroids were tracked and analyzed. The migration distances of drought events exhibited a significant linear relationship with the drought duration (R2 > 0.8, slope of 165 km per month). More than 70% of drought events had a migrating displacement greater than 1° (approximately 100 km). These results indicated that the meteorological drought events traveled actively and occurred on a widespread basis in the basin. Moreover, two main patterns of drought cluster migration (northward and southward) were identified. The approach and findings can provide some important implications to investigate the migration of meteorological droughts in other regions.
Fast Bayesian Regression Kriging Method for Real‐Time Merging of Radar, Rain Gauge, and Crowdsourced Rainfall Data
Authors: Yang Pan , Ng Tze Ling 
Published: April 2019

AbstractCrowdsourcing of rainfall measurements incorporating common citizens as a rich source of data is an emerging concept with huge potential to provide valuable high spatiotemporal resolution rainfall observations. Here we investigate the merging of crowdsourced rainfall data with traditional radar and rain gauge data to maximize their utility. For this purpose, we develop a tailored fast Bayesian regression kriging (FBRK) method combining regression kriging and Laplace approximation in a Bayesian framework. A strength of the FBRK method lies in its ability to capture the differences between rain gauge and crowdsourced measurement errors. Another lies in its fast yet reasonably accurate approximation of the Bayesian posterior, making it suitable to use in real time. We conduct synthetic computer simulations to evaluate the FBRK method alongside three other merging methods. In the simulations, we compare the accuracies of their resulting rainfall estimates, as well as the skill of those estimates as input to a storm water flow forecasting model. In both aspects, we observe the FBRK method to lead to more accurate results and truer representations of the associated uncertainties. However, we also observe the performance of the FBRK method to be sensitive to the choice of the Bayesian prior under certain conditions. Finally, from the synthetic simulations, we find merging crowdsourced data with traditional data to lead to more accurate estimation of the ground truth rainfall field and, subsequently, more accurate flow forecasts (though only when an adequate merging method, e.g., the FBRK method, is used), and the results to be fairly robust to bias in the input crowdsourced data.
Mapped Hydroclimatology of Evapotranspiration and Drainage Runoff Using SMAP Brightness Temperature Observations and Precipitation Information
Authors: Akbar Ruzbeh , Short Gianotti Daniel J. , Salvucci Guido D. , Entekhabi Dara 
Published: April 2019

AbstractThe partitioning of incident precipitation into evapotranspiration, runoff, drainage, storage change, and hydrologic fluxes depends on the soil moisture state. With the availability of global remotely sensed soil moisture fields, the functional dependence of each flux on soil moisture may be identifiable. In this study we develop an observation‐driven approach to map key hydroclimatology fields using remotely sensed soil moisture and gauge‐based precipitation data only. National Aeronautics and Space Administration's Soil Moisture Active Passive (SMAP) low‐frequency microwave brightness temperature observations and precipitation fields, from the National Centers for Environmental Prediction, are the sole inputs into an adjoint‐state variational estimation framework. Furthermore, the proposed methodology does not rely on micrometeorological information, or land surface models. The approach is flexible by design so that almost any partitioning pattern can result from estimation and corresponding evapotranspiration and drainage fields can be quantified. Three‐year averaged summer season evapotranspiration estimates are compared with available vapor flux at in situ AmeriFlux eddy‐covariance sites. Basin‐averaged drainage over major U.S. hydrologic units is also compared with U.S. Geological Survey streamgages measurements. The remote sensing‐based estimated hydroclimate fields explain about 70% of the variance in the in situ measurements. This exploratory study adds to the body of evidence emerging in literature that a significant amount of hydrologic information is encoded in the dynamic fields of remotely sensed soil moisture. Observation‐driven hydroclimate data fields that are independent of land surface models can provide valuable insights into the state of the water cycle and guide future development of land surface models.
Late Eocene Southern Ocean Cooling and Invigoration of Circulation Preconditioned Antarctica for Full‐Scale Glaciation
Authors: Houben Alexander J. P. , Bijl Peter K. , Sluijs Appy , Schouten Stefan , Brinkhuis Henk 
Published: April 2019

AbstractDuring the Eocene‐Oligocene Transition (EOT; 34–33.5 Ma), Antarctic ice sheets relatively rapidly expanded, leading to the first continent‐scale glaciation of the Cenozoic. Declining atmospheric CO2 concentrations and associated feedbacks have been invoked as underlying mechanisms, but the role of the quasi‐coeval opening of Southern Ocean gateways (Tasman Gateway and Drake Passage) and resulting changes in ocean circulation is as yet poorly understood. Definitive field evidence from EOT sedimentary successions from the Antarctic margin and the Southern Ocean is lacking, also because the few available sequences are often incomplete and poorly dated, hampering detailed paleoceanographic and paleoclimatic analysis. Here we use organic dinoflagellate cysts (dinocysts) to date and correlate critical Southern Ocean EOT successions. We demonstrate that widespread winnowed glauconite‐rich lithological units were deposited ubiquitously and simultaneously in relatively shallow‐marine environments at various Southern Ocean localities, starting in the late Eocene (~35.7 Ma). Based on organic biomarker paleothermometry and quantitative dinocyst distribution patterns, we analyze Southern Ocean paleoceanographic change across the EOT. We obtain strong indications for invigorated surface and bottom water circulation at sites affected by polar westward‐flowing wind‐driven currents, including a westward‐flowing Antarctic Countercurrent, starting at about 35.7 Ma. The mechanism for this oceanographic invigoration remains poorly understood. The circum‐Antarctic expression of the phenomenon suggests that, rather than triggered by tectonic deepening of the Tasman Gateway, progressive pre‐EOT atmospheric cooling played an important role. At localities affected by the Antarctic Countercurrent, sea surface productivity increased and simultaneously circum‐Antarctic surface waters cooled. We surmise that combined, these processes contributed to preconditioning the Antarctic continent for glaciation.
Informing Future Risks of Record‐Level Rainfall in the United States
Authors: Sanderson Benjamin M. , Wobus Cameron , Mills Dave , Zarakas Claire , Crimmins Allison , Sarofim Marcus C. , Weaver Chris 
Published: April 2019

AbstractThe changing risk of extreme precipitation is difficult to project. Events are rare by definition, and return periods of heavy precipitation events are often calculated assuming a stationary climate. Furthermore, ensembles of climate model projections are not large enough to fully categorize the tails of the distribution. To address this, we cluster the contiguous United States into self‐similar hydroclimates to estimate changes in the expected frequency of extremely rare events under scenarios of global mean temperature change. We find that, although there is some regional variation, record events are projected in general to become more intense, with 500‐year events intensifying by 10–50% under 2 °C of warming and by 40–100% under 4 °C of warming. This analysis could provide information to inform regional prioritization of resources to improve the resilience of U.S. infrastructure.
Electron Inertial Effects on Linearly Polarized Electromagnetic Ion Cyclotron Waves at Earth's Magnetosphere
Authors: Kim Eun‐Hwa , Johnson Jay R. , Lee Dong‐Hun 
Published: April 2019

AbstractWe discuss a role of the electron inertial effect on linearly polarized electromagnetic ion cyclotron (EMIC) waves at Earth. The linearly polarized EMIC waves have been previously suggested to be generated via mode conversion from the fast compressional wave at the ion‐ion hybrid (IIH) resonance. When the electron inertial effects are neglected, the wave normal angle of the mode‐converted IIH waves is 90° because the wave vector perpendicular to the magnetic field becomes infinite at the IIH resonance. When the electron inertial effect is considered, the mode‐converted IIH waves can propagate across the magnetic field lines, and the wavelength perpendicular to the magnetic field approaches the electron inertial length scale near the Buchsbaum resonance. These waves are referred to as electron inertial waves. Due to the electron inertial effect, the perpendicular wave number to the ambient magnetic field near the IIH resonance remains finite, and the wave normal angle is less than 90°. The wave normal angle where the maximum absorption occurs in a dipole magnetic field is 30–80°, which is consistent with the observed values near the magnetic equator. Therefore, the numerical results suggest that the linearly polarized EMIC wave generated via mode conversion near the IIH resonance can be detected in between the Buchsbaum and the IIH resonance frequencies, and these waves can have normal angle less than 90°.
Paleoproductivity in the SW Pacific Ocean During the Early Holocene Climatic Optimum
Authors: Bostock H. C. , Prebble J. G. , Cortese G. , Hayward B. , Calvo E. , Quirós‐Collazos L. , Kienast M. , Kim K. 
Published: April 2019

AbstractThe oceans are warming, but it is unclear how marine productivity will be affected under future climate change. In this study we examined a wide range of paleoproductivity proxies along a latitudinal transect (36–58°S) in the SW Pacific during the early Holocene climatic optimum, to explore regional patterns of productivity in a slightly warmer‐than‐present world. During the early Holocene there is a small increase in productivity in the subtropical waters, no change at the subtropical frontal zone, and conflicting evidence in records immediately south of the subtropical front, where an increase is inferred from one core site, but not at the other. Evidence for an increase in productivity in Antarctic Surface Waters, south of the polar front, is also equivocal. We infer a small increase in productivity in subtropical waters, and the ocean just south of the subtropical front was associated with changes in the ocean circulation of the SW Pacific, driven by changes in the Southern Hemisphere Westerly Winds split‐jet structure in this region. The relatively modest warming during the early Holocene climatic optimum in the SW Pacific indicates that this time period may provide an analog for future productivity for the midcentury (2055) under Intergovernmental Panel on Climate Change Representative Concentration Pathway 8.5 or for the end of the century (2100) under Representative Concentration Pathway 4.5. However, higher‐resolution, downscaled models, with realistic Southern Hemisphere Westerly Winds, will be necessary to forecast future productivity for this oceanographically complex region.
Actigraphy Technology: Informing Assessment and Intervention for Sleep Disturbances in Young Children
Authors: Eaton Cyd K. , Henning Ellen , Lam Janet , Paasch Valerie 
Published: April 2019

Objective: To demonstrate the clinical feasibility and utility of referring young children (ages 2 to 5 years old) presenting to an interdisciplinary pediatric sleep clinic for objective sleep assessment using actigraphy. Method: A retrospective chart review was conducted to identify young children referred for actigraphy from the sleep clinic. Each referred child wore an actigraph for approximately 1 week; caregivers completed daily sleep diaries to report on children’s estimated bedtime and wake time. Treatment recommendations provided after actigraphy and treatment responses were abstracted via chart review. Results: Of the 88 young children presenting to the sleep clinic during the study period, 11 were referred for and completed actigraphy monitoring. All referred children, including those with neurodevelopmental disabilities, tolerated wearing the actigraph on their wrist. All children were shown to have sleep disturbances via actigraphy results. The most common disturbances were the frequency and duration of night wakings, which reduced total sleep time compared to published norms from a healthy, same-aged sample. All children received behavioral treatment recommendations and the majority were prescribed medication for sleep concerns. The majority of children were considered treatment responders (73%). Conclusions: Actigraphy may be a feasible and informative assessment tool for clinicians to integrate into regular practice with young children to obtain objective sleep data that may not have otherwise been available. Clinical recommendations and practical concerns (e.g., billing) of using actigraphy in an interdisciplinary pediatric setting are discussed. Implications for Impact Statement Pediatric psychologists may implement objective sleep assessments using actigraphy with young children during clinical practice and use the data generated to communicate details about problematic sleep patterns to caregivers, which may inform intervention recommendations.