bluuebunny/crossref_metadata_2025_split huggingface dataset:
Long‐term determination of energetic electron precipitation into the atmosphere from AARDDVARK subionospheric VLF observations
Authors: Neal Jason J. , Rodger Craig J. , Clilverd Mark A. , Thomson Neil R. , Raita Tero , Ulich Thomas 
Published: February 2015

AbstractWe analyze observations of subionospherically propagating very low frequency (VLF) radio waves to determine outer radiation belt energetic electron precipitation (EEP) flux magnitudes. The radio wave receiver in Sodankylä, Finland (Sodankylä Geophysical Observatory) observes signals from the transmitter with call sign NAA (Cutler, Maine). The receiver is part of the Antarctic‐Arctic Radiation‐belt Dynamic Deposition VLF Atmospheric Research Konsortia (AARDDVARK). We use a near‐continuous data set spanning November 2004 until December 2013 to determine the long time period EEP variations. We determine quiet day curves over the entire period and use these to identify propagation disturbances caused by EEP. Long Wave Propagation Code radio wave propagation modeling is used to estimate the precipitating electron flux magnitudes from the observed amplitude disturbances, allowing for solar cycle changes in the ambient D region and dynamic variations in the EEP energy spectra. Our method performs well during the summer months when the daylit ionosphere is most stable but fails during the winter. From the summer observations, we have obtained 693 days worth of hourly EEP flux magnitudes over the 2004–2013 period. These AARDDVARK‐based fluxes agree well with independent satellite precipitation measurements during high‐intensity events. However, our method of EEP detection is 10–50 times more sensitive to low flux levels than the satellite measurements. Our EEP variations also show good agreement with the variation in lower band chorus wave powers, providing some confidence that chorus is the primary driver for the outer belt precipitation we are monitoring.
Low‐latitude scintillation weakening during sudden stratospheric warming events
Authors: de Paula E. R. , Jonah O. F. , Moraes A. O. , Kherani E. A. , Fejer B. G. , Abdu M. A. , Muella M. T. A. H. , Batista I. S. , Dutra S. L. G. , Paes R. R. 
Published: February 2015

AbstractGlobal Positioning System (GPS) L1‐frequency (1.575 GHz) amplitude scintillations at São José dos Campos (23.1°S, 45.8°W, dip latitude 17.3°S), located under the southern crest of the equatorial ionization anomaly, are analyzed during the Northern Hemisphere winter sudden stratospheric warming (SSW) events of 2001/2002, 2002/2003, and 2012/2013. The events occurred during a period when moderate to strong scintillations are normally observed in the Brazilian longitude sector. The selected SSW events were of moderate and major categories and under low Kp conditions. The most important result of the current study is the long‐lasting (many weeks) weakening of scintillation amplitudes at this low‐latitude station, compared to their pre‐SSW periods. Ionosonde‐derived evening vertical plasma drifts and meridional neutral wind effects inferred from total electron content measurements are consistent with the observed weakening of GPS scintillations during these SSW events. This work provides strong evidence of SSW effects on ionospheric scintillations and the potential consequences of such SSW events on Global Navigation Satellite System‐based applications.
Spreading of Levantine Intermediate Waters by submesoscale coherent vortices in the northwestern Mediterranean Sea as observed with gliders
Authors: Bosse Anthony , Testor Pierre , Mortier Laurent , Prieur Louis , Taillandier Vincent , d'Ortenzio Fabrizio , Coppola Laurent 
Published: February 2015

AbstractSince 2007, gliders have been regularly deployed in the northwestern Mediterranean Sea, a crucial region regarding the thermohaline circulation of the Mediterranean Sea. It revealed for the first time very warm (+0.4∘C) and saline (+0.1) submesoscale anticyclones at intermediate depth characterized by a small radius (∼5 km), high Rossby (∼0.3), and Burger (∼0.7) numbers. They are likely order of 10 to be formed each year, have a life time order a year and certainly contribute significantly to the spreading of the Levantine Intermediate Waters (LIW) toward the whole subbasin, thus potentially impacting wintertime vertical mixing through hydrographical and dynamical preconditioning. They could be mainly formed by the combined action of turbulent mixing and flow detachment of the northward flow of LIW at the northwestern headland of Sardinia. Upwelling conditions along the western coast of Sardinia associated with a southward geostrophic flow within the upper layers seem to play a key role in their formation process.
Impact of submesoscale processes on dynamics of phytoplankton filaments
Authors: Shulman Igor , Penta Bradley , Richman James , Jacobs Gregg , Anderson Stephanie , Sakalaukus Peter 
Published: February 2015

AbstractIn Monterey Bay, CA, during northwesterly, upwelling favorable winds, the development of a southward flowing cold jet along the entrance to the Bay is often observed. This dense cold jet separates warm waters of the anticyclonic circulation offshore from the water masses inside the Bay. Interactions between the cold jet and the offshore anticyclonic circulation generate ageostrophic secondary circulation (ASC) cells due to submesoscale processes as, for example, flow interaction with the development of surface frontogenesis and nonlinear Ekman pumping. Based on observations and modeling studies, we evaluate the impact of these submesoscale processes on the formation of chlorophyll a filaments during late spring‐earlier summer, and late summer time frames. We show that during the late summer time frame, ASC leads to the development of filaments with high values of chlorophyll a concentration along the edge of the cold jet–in contrast to the earlier summer time, when the ASC mixes phytoplankton much deeper to the area below of the euphotic depth, and chlorophyll a filaments are 3–4 times weaker.
On the origin and propagation of Denmark Strait overflow water anomalies in the Irminger Basin
Authors: Jochumsen Kerstin , Köllner Manuela , Quadfasel Detlef , Dye Stephen , Rudels Bert , Valdimarsson Heðinn 
Published: February 2015

AbstractDenmark Strait Overflow Water (DSOW) supplies the densest contribution to North Atlantic Deep Water and is monitored at several locations in the subpolar North Atlantic. Hydrographic (temperature and salinity) and velocity time series from three multiple‐mooring arrays at the Denmark Strait sill, at 180 km downstream (south of Dohrn Bank) and at a further 320 km downstream on the east Greenland continental slope near Tasiilaq (formerly Angmagssalik), were analyzed to quantify the variability and track anomalies in DSOW in the period 2007–2012. No long‐term trends were detected in the time series, while variability on time scales from interannual to weekly was present at all moorings. The hydrographic time series from different moorings within each mooring array showed coherent signals, while the velocity fluctuations were only weakly correlated. Lagged correlations of anomalies between the arrays revealed a propagation from the sill of Denmark Strait to the Angmagssalik array in potential temperature with an average propagation time of 13 days, while the correlations in salinity were low. Entrainment of warm and saline Atlantic Water and fresher water from the East Greenland Current (via the East Greenland Spill Jet) can explain the whole range of hydrographic changes in the DSOW measured downstream of the sill. Changes in the entrained water masses and in the mixing ratio can thus strongly influence the salinity variability of DSOW. Fresh anomalies found in downstream measurements of DSOW within the Deep Western Boundary Current can therefore not be attributed to Arctic climate variability in a straightforward way.
Large variability of the Kuroshio at 23.75°N east of Taiwan
Authors: Jan Sen , Yang Yiing Jang , Wang Joe , Mensah Vigan , Kuo Tien‐Hsia , Chiou Ming‐Da , Chern Ching‐Sheng , Chang Ming‐Huei , Chien Hwa 
Published: February 2015

AbstractSynoptic features of the Kuroshio at 23.75°N were quantified using nine ship‐based surveys between September 2012 and September 2014. The new ship‐based data set provides an unprecedented view of the Kuroshio east of Taiwan and suggest tremendous variability in its velocity, hydrography, volume, heat, and salt transports, and water masses. The Kuroshio maximum velocity varied in 0.7–1.4 m s−1; the core current width, delineated with the limit v ≥ 0.2 m s−1, ranged from 85 to 135 km, and the thickness varied from 400 to 600 m. A dual velocity maximum in the Kuroshio core current, though unexpected, was observed in three of nine cruises. The Kuroshio core transport, integrated from the directly measured velocity, varied between 10.46 and 22.92 Sv (1 Sv=106 m3 s−1). The corresponding heat transport referenced to 0°C was 0.838–1.793 × 1015 W, and the salt transport was 345.0–775.9 × 106 kg s−1. The geostrophic transport estimated using the thermal wind relation with the observed hydrographic data and reference velocity at 900 m is comparable to the directly measured Kuroshio transport during most of the surveys, suggesting the directly measured velocity is mostly in geostrophic balance.
Hemispheric asymmetries and seasonality of mean age of air in the lower stratosphere: Deep versus shallow branch of the Brewer‐Dobson circulation
Authors: Konopka Paul , Ploeger Felix , Tao Mengchu , Birner Thomas , Riese Martin 
Published: February 2015

AbstractBased on multiannual simulations with the Chemical Lagrangian Model of the Stratosphere, (CLaMS) driven by ECMWF ERA‐Interim reanalysis, we discuss hemispheric asymmetries and the seasonality of the mean age of air (AoA) in the lower stratosphere. First, the planetary wave forcing of the Brewer‐Dobson circulation is quantified in terms of Eliassen Palm flux divergence calculated by using the isentropic coordinate θ. While the forcing of the deep branch at θ = 1000 K (around 10 hPa) has a clear maximum in each hemisphere during the respective winter, the shallow branch of the Brewer‐Dobson circulation, i.e., between 100 and 70 hPa (380 < θ < 420 K), shows almost opposite seasonality in both hemispheres with a pronounced minimum between June and September in the Southern Hemisphere. Second, we decompose the time‐tendency of AoA into the contributions of the residual circulation and of eddy mixing by analyzing the zonally averaged tracer continuity equation. In the tropical lower stratosphere between ±30°, the air becomes younger during boreal winter and older during boreal summer. During boreal winter, the decrease of AoA due to tropical upwelling outweighs aging by isentropic mixing. In contrast, weaker isentropic mixing outweighs an even weaker upwelling in boreal summer and fall making the air older during these seasons. Poleward of 60°, the deep branch locally increases AoA and eddy mixing locally decreases AoA with the strongest net decrease during spring. Eddy mixing in the Northern Hemisphere outweighs that in the Southern Hemisphere throughout the year.
The summer 2012 Greenland heat wave: In situ and remote sensing observations of water vapor isotopic composition during an atmospheric river event
Authors: Bonne Jean‐Louis , Steen‐Larsen Hans Christian , Risi Camille , Werner Martin , Sodemann Harald , Lacour Jean‐Lionel , Fettweis Xavier , Cesana Grégory , Delmotte Marc , Cattani Olivier , Vallelonga Paul , Kjær Helle Astrid , Clerbaux Cathy , Sveinbjörnsdóttir Árny Erla , Masson‐Delmotte Valérie 
Published: February 2015

AbstractDuring 7–12 July 2012, extreme moist and warm conditions occurred over Greenland, leading to widespread surface melt. To investigate the physical processes during the atmospheric moisture transport of this event, we study the water vapor isotopic composition using surface in situ observations in Bermuda Island, South Greenland coast (Ivittuut), and northwest Greenland ice sheet (NEEM), as well as remote sensing observations (Infrared Atmospheric Sounding Interferometer (IASI) instrument on board MetOp‐A), depicting propagation of similar surface and midtropospheric humidity and δD signals. Simulations using Lagrangian moisture source diagnostic and water tagging in a regional model showed that Greenland was affected by an atmospheric river transporting moisture from the western subtropical North Atlantic Ocean, which is coherent with observations of snow pit impurities deposited at NEEM. At Ivittuut, surface air temperature, humidity, and δD increases are observed. At NEEM, similar temperature increase is associated with a large and long‐lasting ∼100‰δD enrichment and ∼15‰ deuterium excess decrease, thereby reaching Ivittuut level. We assess the simulation of this event in two isotope‐enabled atmospheric general circulation models (LMDz‐iso and ECHAM5‐wiso). LMDz‐iso correctly captures the timing of propagation for this event identified in IASI data but depict too gradual variations when compared to surface data. Both models reproduce the surface meteorological and isotopic values during the event but underestimate the background deuterium excess at NEEM. Cloud liquid water content parametrization in LMDz‐iso poorly impacts the vapor isotopic composition. Our data demonstrate that during this atmospheric river event the deuterium excess signal is conserved from the moisture source to northwest Greenland.
Modeling seismic energy propagation in highly scattering environments
Authors: Blanchette‐Guertin J.‐F. , Johnson C. L. , Lawrence J. F. 
Published: February 2015

AbstractMeteoroid impacts over millions to billions of years can produce a highly fractured and heterogeneous megaregolith layer on planetary bodies such as the Moon that lack effective surface recycling mechanisms. The energy from seismic events on these bodies undergoes scattering in the fractured layer(s) and generates extensive coda wave trains that follow major seismic wave arrivals. The decay properties of these codas are affected by the planetary body's interior structure. To understand the propagation of seismic waves in such media, we model the transmission of seismic energy in highly scattering environments using an adapted phonon method. In this Monte Carlo simulation approach, we track a large number of seismic wavelets as they leave a source and we record the resulting ground deformation each time a wavelet reaches a surface receiver. Our method provides the first numerical global modeling of 3‐D scattering, with user‐defined power law distributions of scatterer length scales and frequency‐dependent intrinsic attenuation, under the assumption of 1‐D background velocity models. We model synthetic signals for simple, but highly scattering interior models and vary the model parameters independently to assess their individual effects on the coda. Results show that the magnitude of the decay times is most affected by the background velocity model, in particular the presence of shallow low‐velocity layers, the event source depth, and the intrinsic attenuation level. The decay times are also controlled to a lesser extent by the size‐frequency distribution of scatterers, the thickness of the scattering layer, and the impedance contrast at the scatterers.
Spectral comparison and stability of red regions on Jupiter
Authors: Simon Amy A. , Sanchez‐Lavega Agustin , Legarreta Jon , Sanz‐Requena Jose Francisco , Perez‐Hoyos Santiago , Garcia‐Melendo Enrique , Carlson Robert W. 
Published: February 2015

AbstractA rare red cyclone visible on Jupiter in 1994 and 1995 falls in a class of vortices that are intensely colored, yet low altitude, unlike the Great Red Spot (GRS). Dynamical modeling indicates that the presence of nearby anticyclones both aids in formation and lead to the destruction of the cyclone. A study of absolute spectral reflectance from Hubble Space Telescope imaging data shows that GRS is not typically the “reddest” region of the planet. Rather, transient red cyclones and the reddest parts of the North Equatorial Belt show less reflectance than the GRS at all wavelengths, with enhanced absorption at wavelengths near 500 nm. Temporal analysis shows that the darkest regions of the North Equatorial Belt and transient red cyclones are relatively constant in color from 1995 to 2014, while the spectral slope and absolute brightness of the GRS core vary over time. Laboratory data of colored materials that yield a good qualitative fit to the GRS spectrum do not match the spectra of other regions, and wavelengths from 400 to 700 nm may be most diagnostic of chromophore identification.
Maskelynite formation via solid‐state transformation: Evidence of infrared and X‐ray anisotropy
Authors: Jaret Steven J. , Woerner William R. , Phillips Brian L. , Ehm Lars , Nekvasil Hanna , Wright Shawn P. , Glotch Timothy D. 
Published: February 2015

AbstractWe present the results of a combined study of shocked labradorite from the Lonar crater, India, using optical microscopy, micro‐Raman spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, high‐energy X‐ray total scattering experiments, and micro‐Fourier transform infrared (micro‐FTIR) spectroscopy. We show that maskelynite of shock class 2 is structurally more similar to fused glass than to crystalline plagioclase. However, there are slight but significant differences—preservation of original preimpact igneous zoning, anisotropy at infrared wavelengths, X‐ray anisotropy, and preservation of some intermediate range order—which are all consistent with a solid‐state transformation from plagioclase to maskelynite.
A study of the composition, characteristics, and origin of modern driftwood on the western coast of Nunavik (Quebec, Canada)
Authors: Steelandt Stéphanie , Marguerie Dominique , Bhiry Najat , Delwaide Ann 
Published: February 2015

AbstractData concerning driftwood is of value to researchers in fields as diverse as oceanography, geomorphology, and human occupation. Yet studies on the subject in the Canadian Arctic have only recently been carried out, and the present study is the first in Nunavik (northeastern Canada). This paper documents the composition, characteristics, and origin of modern driftwood pieces on the beaches of the eastern coast of Hudson Bay. A total of 1057 samples from Ivujivik, Akulivik, Inukjuak, and Umiujaq were identified as belonging to four coniferous species (Picea sp., Larix sp., Abies sp. likely balsamea, and Thuja sp. likely occidentalis) and four deciduous species (Salix sp., Populus sp., Alnus sp., and Betula sp., likely papyrifera). Spruce largely predominate; white birch, white cedar, and fir are rare. The presence of the latter species proves that some of the wood originated from south‐southeast of James Bay. Driftwood found in the southern area (Umiujaq) are more numerous, larger, and less degraded than driftwood in the north (Ivujivik). However, many large coniferous samples were found as far north as Akulivik, indicating that they likely traveled a great distance, unlike the smaller wood specimens (especially deciduous samples). All of the wood that we analyzed died relatively young, with an average age of 63 years for conifers and 23 years for deciduous. Measurements of ring widths and the cross‐dating of samples with existing reference chronologies of living trees along Hudson Bay and James Bay revealed several possible correlations and origins for wood found in same areas.
Thermodynamics in the hydrologic response: Travel time formulation and application to Alpine catchments
Authors: Comola F. , Schaefli B. , Rinaldo A. , Lehning M. 
Published: February 2015

AbstractThis paper presents a spatially explicit model for hydrothermal response simulations of Alpine catchments, accounting for advective and nonadvective energy fluxes in stream networks characterized by arbitrary degrees of geomorphological complexity. The relevance of the work stems from the increasing scientific interest concerning the impacts of the warming climate on water resources management and temperature‐controlled ecological processes. The description of the advective energy fluxes is cast in a travel time formulation of water and energy transport, resulting in a closed form solution for water temperature evolution in the soil compartment. The application to Alpine catchments hinges on the boundary conditions provided by the fully distributed and physically based snow model Alpine3D. The performance of the simulations is illustrated by comparing modeled and measured hydrographs and thermographs at the outlet of the Dischma catchment (45 km2) in the Swiss Alps. The Monte Carlo calibration shows that the model is robust and that a simultaneous fitting of streamflow and stream temperature reduces the uncertainty in the hydrological parameters estimation. The calibrated model also provides a good fit to the measurements in the validation period, suggesting that it could be employed for predictive applications, both for hydrological and ecological purposes. The temperature of the subsurface flow, as described by the proposed travel time formulation, proves warmer than the stream temperature during winter and colder during summer. Finally, the spatially explicit results of the model during snowmelt show a notable hydrothermal spatial variability in the river network, owing to the small spatial correlation of infiltration and meteorological forcings in Alpine regions.
Investigation of Thermomechanical Properties of UHMWPE/Graphene Oxide Nanocomposites Prepared by In situ Ziegler–Natta Polymerization
Authors: Bahrami Hiva , Ramazani S. A. Ahmad , Kheradmand Amanj , Shafiee Mojtaba , Baniasadi Hossein 
Published: February 2015

ABSTRACTThe graphene‐based Ziegler–Natta catalyst has been used to prepare ultrahigh molecular weight polyethylene/graphene oxide (UHMWPE/GO) nanocomposite via in situ polymerization. The morphological investigations have been conducted using X‐ray diffraction patterns and scanning electron microscopy method. The obtained results indicated that no diffraction peak is detected in a GO pattern, which could be due to the exfoliation of graphene nanosheets in the UHMWPE matrix. Morphological investigations indicated that GO nanosheets are dispersed almost uniformly in polymeric matrix, and that there should exist a good interaction between nanofillers and matrix. The mechanical properties of the nanocomposites were studied, and the results showed that the Young (tensile) modulus and tensile strength of the prepared nanocomposites were significantly increased by increasing the filler content, which should be due to the high aspect ratio of GO plates and their uniform dispersion in the UHMWPE matrix. The thermogravimetery investigations reveal that the thermal stability of nanocomposites increase with increasing GO content and that initiation thermal decomposition temperature shifts to higher values.