bluuebunny/crossref_metadata_2025_split huggingface dataset:
Incorporating an advanced aerosol activation parameterization into WRF‐CAM5: Model evaluation and parameterization intercomparison
Authors: Zhang Yang , Zhang Xin , Wang Kai , He Jian , Leung L. Ruby , Fan Jiwen , Nenes Athanasios 
Published: June 2015

AbstractAerosol activation into cloud droplets is an important process that governs aerosol indirect effects. The advanced treatment of aerosol activation by Fountoukis and Nenes (2005) and its recent updates, collectively called the FN series, have been incorporated into a newly developed regional coupled climate‐air quality model based on the Weather Research and Forecasting model with the physics package of the Community Atmosphere Model version 5 (WRF‐CAM5) to simulate aerosol‐cloud interactions in both resolved and convective clouds. The model is applied to East Asia for two full years of 2005 and 2010. A comprehensive model evaluation is performed for model predictions of meteorological, radiative, and cloud variables, chemical concentrations, and column mass abundances against satellite data and surface observations from air quality monitoring sites across East Asia. The model performs overall well for major meteorological variables including near‐surface temperature, specific humidity, wind speed, precipitation, cloud fraction, precipitable water, downward shortwave and longwave radiation, and column mass abundances of CO, SO2, NO2, HCHO, and O3 in terms of both magnitudes and spatial distributions. Larger biases exist in the predictions of surface concentrations of CO and NOx at all sites and SO2, O3, PM2.5, and PM10 concentrations at some sites, aerosol optical depth, cloud condensation nuclei over ocean, cloud droplet number concentration (CDNC), cloud liquid and ice water path, and cloud optical thickness. Compared with the default Abdul‐Razzack Ghan (2000) parameterization, simulations with the FN series produce ~107–113% higher CDNC, with half of the difference attributable to the higher aerosol activation fraction by the FN series and the remaining half due to feedbacks in subsequent cloud microphysical processes. With the higher CDNC, the FN series are more skillful in simulating cloud water path, cloud optical thickness, downward shortwave radiation, shortwave cloud forcing, and precipitation. The model evaluation identifies several areas of improvements including emissions and their vertical allocation as well as model formulations such as aerosol formation, cloud droplet nucleation, and ice nucleation.
Construction and destruction of Mont Pelée volcano: Volumes and rates constrained from a geomorphological model of evolution
Authors: Germa Aurelie , Lahitte Pierre , Quidelleur Xavier 
Published: June 2015

AbstractThis study presents long‐term volumes and construction rates for the Mont Conil‐Mont Pelée volcano and rate estimates at which volcanic activity creates relief. An algorithm, ShapeVolc, is used to numerically model topographic surfaces. Volcano morphology is analyzed using current digital elevation model in combination with mapped geology to produce 10 paleotopographies at the end of four constructional stages and three destructional events. Volumes of each constructional stage were estimated at about 35.2 km3, 26.2 km3, 8.3 km3, and 2.5 km3 for a total cumulative erupted volume of 72.2 km3. We estimate that Mont Pelée accounted for about 10% of the Lesser Antilles arc production in the last 100 kyr. The volcano has been built at an average rate of 0.13 km3/kyr during the last 550 kyr. During that time, construction rates varied by a factor of 15, from 0.04 km3/kyr in early stages up to 0.52 km3/kyr after the second flank collapse. Volumes displaced by each flank collapse were estimated at 14.7 km3, 8.8 km3, and 3.5 km3, thus about 37% of the total constructed volume. Integrated over the volcano's lifetime, the rate at which flank collapses removed material off the island is 0.15 km3/kyr. In contrast, long‐term erosion rates outside collapsed areas are estimated at about 0.05 ± 0.7 km3/kyr, or ~11 km3 of material removed. This latter rate is not negligible, which strengthens the importance of taking into account recurrent small erosional events on the geomorphological evolution of a volcanic island in a tropical context.
Palynological evidence for late Quaternary climate and marine primary productivity changes along the California margin
Authors: Pospelova Vera , Price Andrea M. , Pedersen Thomas F. 
Published: June 2015

AbstractA high‐resolution sedimentary record of dinoflagellate cysts from Ocean Drilling Program Hole 1017E (off Point Conception, California margin) reflects how marine primary productivity has changed in response to major shifts in climate and ocean circulation along the California margin over the past 42 kyr. Throughout the studied sequence, dinoflagellate cyst assemblages are dominated by upwelling‐related taxa, signifying the continued presence of coastal upwelling on the margin during the late Quaternary. The cyst record suggests that marine primary productivity was enhanced during the Holocene and Bølling, and to a lesser extent, during the late glacial and most Dansgaard‐Oeschger events, while an apparent reduction in primary productivity can be seen during the Younger Dryas. The best analogue technique, based on a modern dinoflagellate cyst assemblage database from the northeast Pacific, was used for quantitative reconstruction of past sea surface conditions. It points to dynamic changes in annual marine primary productivity (~235–331 g C m−2 yr−1) and sea surface temperature (~10.1–12.6°C in winter; ~13.1–14.3°C in summer), while sea surface salinity appears to be confined to a narrower range (~32.9–33.4 in summer). Our results also indicate noticeable climate variability during the Holocene in this region.
New insights into landslide processes around volcanic islands from Remotely Operated Vehicle (ROV) observations offshore Montserrat
Authors: Watt S. F. L. , Jutzeler M. , Talling P. J. , Carey S. N. , Sparks R. S. J. , Tucker M. , Stinton A. J. , Fisher J. K. , Wall‐Palmer D. , Hühnerbach V. , Moreton S. G. 
Published: June 2015

AbstractSubmarine landslide deposits have been mapped around many volcanic islands, but interpretations of their structure, composition, and emplacement are hindered by the challenges of investigating deposits directly. Here we report on detailed observations of four landslide deposits around Montserrat collected by Remotely Operated Vehicles, integrating direct imagery and sampling with sediment core and geophysical data. These complementary approaches enable a more comprehensive view of large‐scale mass‐wasting processes around island‐arc volcanoes than has been achievable previously. The most recent landslide occurred at 11.5–14 ka (Deposit 1; 1.7 km3) and formed a radially spreading hummocky deposit that is morphologically similar to many subaerial debris‐avalanche deposits. Hummocks comprise angular lava and hydrothermally altered fragments, implying a deep‐seated, central subaerial collapse, inferred to have removed a major proportion of lavas from an eruptive period that now has little representation in the subaerial volcanic record. A larger landslide (Deposit 2; 10 km3) occurred at ∼130 ka and transported intact fragments of the volcanic edifice, up to 900 m across and over 100 m high. These fragments were rafted within the landslide, and are best exposed near the margins of the deposit. The largest block preserves a primary stratigraphy of subaerial volcanic breccias, of which the lower parts are encased in hemipelagic mud eroded from the seafloor. Landslide deposits south of Montserrat (Deposits 3 and 5) indicate the wide variety of debris‐avalanche source lithologies around volcanic islands. Deposit 5 originated on the shallow submerged shelf, rather than the terrestrial volcanic edifice, and is dominated by carbonate debris.
Crustal‐scale degassing due to magma system destabilization and magma‐gas decoupling at Soufrière Hills Volcano, Montserrat
Authors: Christopher T. E. , Blundy J. , Cashman K. , Cole P. , Edmonds M. , Smith P. J. , Sparks R. S. J. , Stinton A. 
Published: June 2015

AbstractActivity since 1995 at Soufrière Hills Volcano (SHV), Montserrat has alternated between andesite lava extrusion and quiescence, which are well correlated with seismicity and ground deformation cycles. Large variations in SO2 flux do not correlate with these alternations, but high and low HCl/SO2 characterize lava dome extrusion and quiescent periods respectively. Since lava extrusion ceased (February 2010) steady SO2 emissions have continued at an average rate of 374 tonnes/day (± 140 t/d), and incandescent fumaroles (temperatures up to 610oC) on the dome have not changed position or cooled. Occasional short bursts (over several hours) of higher (∼ 10x) SO2 flux have been accompanied by swarms of volcano‐tectonic earthquakes. Strain data from these bursts indicate activation of the magma system to depths up to 10 km. SO2 emissions since 1995 greatly exceed the amounts that could be derived from 1.1 km3 of erupted andesite, and indicating extensive partitioning of sulfur into a vapour phase, as well as efficient decoupling and outgassing of sulfur‐rich gases from the magma. These observations are consistent with a vertically extensive, crustal magmatic mush beneath SHV. Three states of the magmatic system are postulated to control degassing. During dormant periods (103 to 104 years) magmatic vapour and melts separate as layers from the mush and decouple from each other. In periods of unrest (years) without eruption, melt and fluid layers become unstable, ascend and can amalgamate. Major destabilization of the mush system leads to eruption, characterized by magma mixing and release of volatiles with different ages, compositions and sources.
Assessment of future changes in water availability and aridity
Authors: Greve P. , Seneviratne S. I. 
Published: June 2015

AbstractSubstantial changes in the hydrological cycle are projected for the 21st century, but these projections are subject to major uncertainties. In this context, the “dry gets drier, wet gets wetter” (DDWW) paradigm is often used as a simplifying summary. However, recent studies cast doubt on the validity of the paradigm and also on applying the widely used P − E (precipitation − evapotranspiration) metric over global land surfaces. Here we show in a comprehensive CMIP5‐based assessment that projected changes in mean annual P − E are generally not significant, except for high‐latitude regions showing wetting conditions until the end of the 21st century. Significant increases in aridity do occur in many subtropical and also adjacent humid regions. However, combining both metrics still shows that approximately 70% of all land area will not experience significant changes. Based on these findings, we conclude that the DDWW paradigm is generally not confirmed for projected changes in most land areas.
Coordinated lightning, balloon‐borne electric field, and radar observations of triggered lightning flashes in North Florida
Authors: MacGorman D. R. , Biggerstaff M. I. , Waugh S. , Pilkey J. T. , Uman M. A. , Jordan D. M. , Ngin T. , Gamerota W. R. , Carrie G. , Hyland P. 
Published: June 2015

AbstractThis study examines coordinated storm and triggered lightning observations made in July–August 2013 at the International Center for Lightning Research and Testing to determine why triggered flashes in Florida typically transition from an upward vertical channel entering the cloud to horizontal structure near the storm's melting level. Data from a balloon‐borne electric field meter, a mobile 5 cm wavelength radar, and a small‐baseline VHF Lightning Mapping Array acquired during a period in which three flashes were triggered on 1 August confirmed the hypothesis that the transition to horizontal lightning structure just above the melting level occurred in a layer of negative charge. This experiment was the first to provide vertical profiles of the electric field in Florida storms, from which their vertical charge distribution could be inferred. Three dissipating storms observed on different days all had negative charge near the melting level, but a growing mature storm had positive charge there.
Microscopic structural change in a liquid Fe‐C alloy of ~5 GPa
Authors: Shibazaki Yuki , Kono Yoshio , Fei Yingwei 
Published: June 2015

AbstractThe structure of a liquid Fe‐3.5 wt % C alloy is examined for up to 7.2 GPa via multiangle energy‐dispersive X‐ray diffraction using a Paris‐Edinburgh type large‐volume press. X‐ray diffraction data show clear changes in the pressure‐dependent peak positions of structure factor and reduced pair distribution function at 5 GPa. These results suggest that the liquid Fe‐3.5 wt % C alloys change structurally at approximately 5 GPa. This finding serves as a microscopic explanation for the alloy's previously observed density change at the same pressure. The pressure dependencies of the nearest and second neighbor distances of the liquid Fe‐3.5 wt % C alloy are similar to those of liquid Fe which exhibits a structural change near the bcc‐fcc‐liquid triple point (5.2 GPa and 1991 K). Similarities between Fe‐3.5 wt % C and Fe suggest that a density change also occurs in liquid Fe and that this structural change extends to other Fe‐light element alloys.
The existence of radial anisotropy in Earth's upper inner core revealed from seismic normal mode observations
Authors: Lythgoe Karen H. , Deuss Arwen 
Published: June 2015

AbstractAs we strive to understand the most remote region of our planet, one critical area of investigation is the uppermost inner core since its structure is related to solidification of outer core material at the inner core boundary (ICB). Previous seismic studies have used body waves to show that the top ∼100 km of the inner core is isotropic. However, radial anisotropy cannot be uniquely determined by body wave observations. Alternatively, normal mode center frequencies are sensitive to spherically symmetric Earth structure, therefore may provide a constraint on the existence of radial anisotropy in the inner core. Here we show that normal mode center frequency measurements are compatible with 2–5% radial anisotropy in the top ∼100 km of the inner core with a fast direction radially outward and a slow direction along the ICB. Given the uncertainties in the mineral physics and processes that produce anisotropy, the observed radial anisotropy may be reconciled with predictions based on either solidification processes or from texturing due to anisotropic growth.
Warm‐air advection, air mass transformation and fog causes rapid ice melt
Authors: Tjernström Michael , Shupe Matthew D. , Brooks Ian M. , Persson P. Ola G. , Prytherch John , Salisbury Dominic J. , Sedlar Joseph , Achtert Peggy , Brooks Barbara J. , Johnston Paul E. , Sotiropoulou Georgia , Wolfe Dan 
Published: June 2015

AbstractDirect observations during intense warm‐air advection over the East Siberian Sea reveal a period of rapid sea‐ice melt. A semistationary, high‐pressure system north of the Bering Strait forced northward advection of warm, moist air from the continent. Air‐mass transformation over melting sea ice formed a strong, surface‐based temperature inversion in which dense fog formed. This induced a positive net longwave radiation at the surface while reducing net solar radiation only marginally; the inversion also resulted in downward turbulent heat flux. The sum of these processes enhanced the surface energy flux by an average of ~15 W m−2 for a week. Satellite images before and after the episode show sea‐ice concentrations decreasing from > 90% to ~50% over a large area affected by the air‐mass transformation. We argue that this rapid melt was triggered by the increased heat flux from the atmosphere due to the warm‐air advection.
Optical emissions associated with energetic electrons produced by stepping leaders in cloud‐to‐ground lightning discharges
Authors: Xu Wei , Celestin Sebastien , Pasko Victor P. 
Published: June 2015

AbstractBoth natural cloud‐to‐ground and rocket‐triggered lightning flashes have been found to be associated with intense and brief bursts of X‐ray emissions. Using a full energy Monte Carlo model combined with an optical emission model, we quantify the optical emissions induced by the strong acceleration of thermal runaway electrons in the highly inhomogeneous electric field produced by stepping lightning leaders. The results demonstrate that this acceleration process is accompanied with not only high‐energy X‐ray emissions but also detectable levels of optical emissions. The fluorescence beam exhibits a conical shape and appears to be larger than the streamer zone associated with the lightning leader. Moreover, we emphasize that the size of the fluorescence beam largely depends on the electrical properties of the associated lightning leader and the intensity ratio between emissions from the second positive band system of N2 and the first negative band system of N
reflects the intrinsic difference in the energetics of electrons involved. Therefore, corresponding measurements compared to modeling results can provide useful information for understanding of the stepping mechanism of lightning leaders and associated X‐ray production processes.
Bottom water export from the western Ross Sea, 2007 through 2010
Authors: Gordon Arnold L. , Huber Bruce A. , Busecke Julius 
Published: June 2015

AbstractBottom water export from the Ross Sea, February 2007 to January 2011, exhibits seasonal and interannual variability. Temperature minima coupled to salinity maxima in late austral summer, into the fall, indicate input from High‐Salinity Shelf Water (HSSW). Secondary temperature minima lacking the high‐salinity trait, characteristic of Low‐Salinity Shelf Water (LSSW), appear in the spring. Warmer bottom water similar to modified Circumpolar Deep Water (mCDW) is observed in winter and in early summer. The LSSW and mCDW may be drawn from the Drygalski Basin, as the HSSW pool retreats poleward from the shelf break in response to increased winter polar easterlies allowing these less dense overlying waters to spill into the deep ocean within the benthic layer. Bottom salinity decreased from 2007 to 2011 by 0.007 year−1 significantly higher than regional decadal trends, which we propose is a result of HSSW retreat induced by strengthening polar easterlies.
An electrical conductivity model for fractal porous media
Authors: Wei Wei , Cai Jianchao , Hu Xiangyun , Han Qi 
Published: June 2015

AbstractArchie's equation is an empirical electrical conductivity‐porosity model that has been used to predict the formation factor of porous rock for more than 70 years. However, the physical interpretation of its parameters, e.g., the cementation exponent m, remains questionable. In this study, a theoretical electrical conductivity equation is derived based on the fractal characteristics of porous media. The proposed model is expressed in terms of the tortuosity fractal dimension (DT), the pore fractal dimension (Df), the electrical conductivity of the pore liquid, and the porosity. The empirical parameter m is then determined from physically based parameters, such as DT and Df. Furthermore, a distinct interrelationship between DT and Df is obtained. We find a reasonably good match between the predicted formation factor by our model and experimental data.
Hydrogen self‐diffusivity in single crystal ringwoodite: Implications for water content and distribution in the mantle transition zone
Authors: Sun Wei , Yoshino Takashi , Sakamoto Naoya , Yurimoto Hisayoshi 
Published: June 2015

AbstractHydrogen lattice diffusion in Fe‐bearing ringwoodite was investigated through hydrogen and deuterium interdiffusing in a pair of synthesized single crystals at various temperatures (1000–1300 K) at 21 GPa. Diffusion profiles were investigated by secondary ion mass spectrometer to determine the hydrogen self‐diffusivity in ringwoodite. Temperature dependences of hydrogen diffusion in ringwoodite were determined to be DH = 10− 7.29(±0.46) exp[−101(±10)kJ mol− 1/RT] m2/s in ringwoodite at 21 GPa. The proton conductivities of ringwoodite estimated from the present diffusion coefficients are similar to those of Yoshino et al. [2008] at the transition zone condition at low water content (<1000 ppm by weight (ppmw)) but lower at higher water content range (>1000 ppmw). If the proton‐vacancy mechanism is assumed to be a main controlling mechanism, contribution of water to the electrical conductivity of ringwoodite is insignificant due to large contribution of hopping conduction at the transition zone condition, and global average water concentration in the lower part of transition zone is less than 1000 ppmw.
Detections of lunar exospheric ions by the LADEE neutral mass spectrometer
Authors: Halekas J. S. , Benna M. , Mahaffy P. R. , Elphic R. C. , Poppe A. R. , Delory G. T. 
Published: June 2015

AbstractThe Lunar Atmosphere and Dust Environment Explorer (LADEE) Neutral Mass Spectrometer (NMS), operating in ion mode, provides sensitive detections of ions from the lunar exosphere. By analyzing ion‐mode data from the entire mission, utilizing Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon's Interaction with the Sun (ARTEMIS) plasma and magnetic field measurements to organize NMS data and eliminate background sources, we identify highly significant detections of lunar ions at mass per charge of 2, 4, 12, 20, 28, 39, and 40, moderately significant detections at 14 and 23, and weak detections at 24, 25, and 36. Unlike many previous observations of Moon‐derived ions, an outward pointing viewing geometry ensures that these ions originate from the exosphere, rather than directly from the surface. For species with known neutral distributions, inferred ion production rates appear consistent with expectations for both magnitude and spatial distribution, assuming photoionization as the predominant source mechanism. Unexpected signals at mass per charge 12 and 28 suggest the presence of a significant exospheric population of carbon‐bearing molecules.
A 20 year decline in solar photospheric magnetic fields: Inner‐heliospheric signatures and possible implications
Authors: Janardhan P. , Bisoi Susanta Kumar , Ananthakrishnan S. , Tokumaru M. , Fujiki K. , Jose L. , Sridharan R. 
Published: June 2015

AbstractWe report observations of a steady 20 year decline of solar photospheric fields at latitudes ≥45° starting from ∼1995. This prolonged and continuing decline, combined with the fact that cycle 24 is already past its peak, implies that magnetic fields are likely to continue to decline until ∼2020, the expected minimum of the ongoing solar cycle 24. In addition, interplanetary scintillation observations of the inner heliosphere for the period 1983–2013 and in the distance range 0.2–0.8 AU have also shown a similar and steady decline in solar wind microturbulence levels, in sync with the declining photospheric fields. Using the correlation between the polar field and heliospheric magnetic field (HMF) at solar minimum, we have estimated the value of the HMF in 2020 to be 3.9 (±0.6) nT and a floor value of the HMF of ∼3.2 (±0.4) nT. Given this floor value for the HMF, our analysis suggests that the estimated peak sunspot number for solar cycle 25 is likely to be 62 (±12).