bluuebunny/crossref_metadata_2025_split huggingface dataset:
Magnetotelluric investigation of the Vestfold Hills and Rauer Group, East Antarctica
Authors: Peacock J. R. , Selway K. 
Published: April 2016

AbstractThe Vestfold Hills and Rauer Group in East Antarctica have contrasting Archean to Neoproterozoic geological histories and are believed to be juxtaposed along a suture zone that now lies beneath the Sørsdal Glacier. Exact location and age of this suture zone are unknown, as is its relationship to regional deformation associated with the amalgamation of East Gondwana. To image the suture zone, magnetotelluric (MT) data were collected in Prydz Bay, East Antarctica, mainly along a profile crossing the Sørsdal Glacier and regions inland of the Vestfold Hills and Rauer Group islands. Time‐frequency analysis of the MT time series yielded three important observations: (1) Wind speeds in excess of ∼8 m/s reduce coherence between electric and magnetic fields due to charged wind‐blown particles of ice and snow. (2) Estimation of the MT transfer function is best between 1000 and 1400 UT when ionospheric Hall currents enhance the magnetic source field. (3) Nonplanar source field effects were minimal but detectable and removed from estimation of the MT transfer function. Inversions of MT data in 2‐D and 3‐D produce similar resistivity models, where structures in the preferred 3‐D resistivity model correlate strongly with regional magnetic data. The electrically conductive Rauer Group is separated from the less conductive Vestfold Hills by a resistive zone under the Sørsdal Glacier, which is interpreted to be caused by oxidation during suturing. Though a suture zone has been imaged, no time constrains on suturing can be made from the MT data.
The Cenozoic growth of the Qilian Shan in the northeastern Tibetan Plateau: A sedimentary archive from the Jiuxi Basin
Authors: Wang Weitao , Zhang Peizhen , Pang Jianzhang , Garzione Carmala , Zhang Huiping , Liu Caicai , Zheng Dewen , Zheng Wenjun , Yu Jingxing 
Published: April 2016

AbstractSedimentary deposits in Tibetan Basins archive the spatial‐temporal patterns of the deformation and surface uplift processes that created the area's high topography during the Cenozoic India‐Asia collision. In this study, new stratigraphic investigation of the Caogou section from the Jiuxi Basin in the northeasternmost part of Tibetan Plateau provides chronologic constraints on the deformation and northward growth of the plateau. Magnetostratigraphic analysis results suggest that the age of the studied ~1000 m thick section spans from ~24.2 Ma to 2.8 Ma. Detailed sedimentology and apatite fission track (AFT) analyses reveal that variations in the clast provenance, lithofacies, sediment accumulation rates, and AFT lag times occurred at ~13.5–10.5 Ma. We interpret these changes as in response to the initial uplift of the North Qilian Shan. In addition, paleomagnetic declination results from the section indicate a clockwise rotation of the Jiuxi Basin before ~13.5 Ma, which was followed by a subsequent counterclockwise rotation during 13.5–9 Ma. This reversal in rotation direction may be directly related to left‐lateral strike‐slip activity along the easternmost segment of the Altyn Tagh Fault. Combined with previous studies, we suggest that movement on the western part of the Altyn Tagh Fault was probably initiated during the Oligocene (>30 Ma) and that fault propagation to its eastern tip occurred during the middle‐late Miocene.
New insights into Phanerozoic tectonics of south China: Part 1, polyphase deformation in the Jiuling and Lianyunshan domains of the central Jiangnan Orogen
Authors: Li Jianhua , Dong Shuwen , Zhang Yueqiao , Zhao Guochun , Johnston Stephen T. , Cui Jianjun , Xin Yujia 
Published: April 2016

AbstractThe central Jiangnan Orogen, genetically formed by the Proterozoic Yangtze‐Cathaysia collision, presents as a composite structural feature in the Phanerozoic with multiple ductile and brittle fabrics whose geometries, kinematics, and ages are crucial to decipher the tectonic evolution of south China. New structural observations coupled with thermochronological and geochronological studies of these fabrics document four main stages of deformation. The earliest stage in early Paleozoic time (460–420 Ma) corresponds to combined E‐trending dextral and northwest directed thrust shearing that was variably partitioned in anastomosing high‐strain zones under greenschist‐facies conditions (~400–500°C), related to the continued Yangtze‐Cathaysia convergence externally driven by the suturing of south China with Australia. This event was heterogeneously overprinted by the second stage characterized by ~E‐oriented folding in middle Triassic time, geodynamically resulting from the continental collision of south China with Indochina and North China. The third stage was locally developed by northwest and southeast vergent thrusts that truncated ~E‐oriented folds in the Late Jurassic, due to northwestward subduction of the Paleo‐Pacific plate. The latest stage involved normal faulting and tectonic unroofing in Cretaceous time, which resulted in basin opening and reset footwall40Ar/39Ar ages in proximity to the Hengshan detachment fault, associated with roll‐back of the subducting Paleo‐Pacific plate.
Focusing of baroclinic tidal energy in a canyon
Authors: Vlasenko Vasiliy , Stashchuk Nataliya , Inall Mark E. , Porter Marie , Aleynik Dmitry 
Published: April 2016

AbstractStrong three‐dimensional focusing of internal tidal energy in the Petite Sole Canyon in the Celtic Sea is analyzed using observational data and numerical modeling. In a deep layer (500–800 m) in the center of the canyon, shear variance was elevated by an order of magnitude. Corresponding large vertical oscillations of deep isotherms and a local maximum of horizontal velocity were replicated numerically using the MITgcm. The elevated internal tidal activity in the deep part of the canyon is explained in terms of the downward propagation and focusing of multiple internal tidal beams generated at the shelf break. The near‐circular shape of the canyon head and steep bottom topography throughout the canyon (steeper than the tidal beam) create favorable conditions for the lens‐like focusing of tidal energy in the canyon's center. Observations and modeling show that the energy focusing greatly intensifies local diapycnal mixing that leads to local formation of a baroclinic eddy.
Turbulent flow field and air entrainment in laboratory plunging breaking waves
Authors: Na Byoungjoon , Chang Kuang‐An , Huang Zhi‐Cheng , Lim Ho‐Joon 
Published: April 2016

AbstractThis paper presents laboratory measurements of turbulent flow fields and void fraction in deep‐water plunging breaking waves using imaging and optical fiber techniques. Bubble‐size distributions are also determined based on combined measurements of velocity and bubble residence time. The most excited mode of the local intermittency measure of the turbulent flow and its corresponding length scale are obtained using a wavelet‐based method and found to correlate with the swirling strength and vorticity. Concentrated vortical structures with high intermittency are observed near the lower boundaries of the aerated rollers where the velocity shear is high; the length scale of the deduced eddies ranges from 0.05 to 0.15 times the wave height. The number of bubbles with a chord length less than 2 mm demonstrates good correlation with the swirling strength. The power‐law scaling and the Hinze scale of the bubbles determined from the bubble chord length distribution compare favorably with existing measurements. The turbulent dissipation rate, accounting for void fraction, is estimated using mixture theory. When void fraction is not considered, the turbulent dissipation rate is underestimated by more than 70% in the initial impinging and the first splash‐up roller. A significant discrepancy of approximately 67% between the total energy dissipation rate and the turbulence dissipation rate is found. Of this uncounted dissipation, 23% is caused by bubble‐induced dissipation.
Infragravity waves on fringing reefs in the tropical Pacific: Dynamic setup
Authors: Becker J. M. , Merrifield M. A. , Yoon H. 
Published: April 2016

AbstractCross‐shore pressure and current observations from four fringing reefs of lengths ranging from 135 to 420 m reveal energetic low‐frequency (∼0.001–0.05 Hz) motions. The spatial structure and temporal amplitudes of an empirical orthogonal function analysis of the pressure measurements suggest the dominant low‐frequency variability is modal. Incoming and outgoing linear flux estimates also support partially standing modes on the reef flat during energetic events. A cross‐covariance analysis suggests that breakpoint forcing excites these partially standing modes, similar to previous findings at other steep reefs. The dynamics of Symonds et al. (1982) with damping are applied to a step reef, with forcing obtained by extending a point break model of Vetter et al. (2010) for breaking wave setup to the low‐frequency band using the shoaled envelope of the incident free surface elevation. A one parameter, linear analytical model for the reef flat free surface elevation is presented, which describes between 75% and 97% of the variance of the observed low‐frequency shoreline significant wave height for all reefs considered over a range of conditions. The linear model contains a single dimensionless parameter that is the ratio of the inertial to dissipative time scales, and the observations from this study exhibit more low‐frequency variability when the dissipative time scale is greater than the inertial time scale for the steep reefs considered.
Hygroscopicity and CCN activity of atmospheric aerosol particles and their relation to organics: Characteristics of urban aerosols in Nagoya, Japan
Authors: Kawana Kaori , Nakayama Tomoki , Mochida Michihiro 
Published: April 2016

AbstractThe size‐resolved distributions of hygroscopic growth factor g and the ratios of cloud condensation nuclei (CCN) to condensation nuclei of atmospheric aerosols were investigated in Nagoya, Japan. The average of the distributions of g at 85% relative humidity was bimodal. The size‐resolved mean κ derived from g showed an increasing trend with diameter: 0.17–0.33 at 24–359 nm. The κ values calculated from CCN activation curves were 37% higher than those derived from g. Only 9% of the 37% difference is explained by the difference in the κ of inorganics under subsaturated and supersaturated conditions, suggesting a contribution of organics to the remaining 28% difference. The size‐averaged κ of organics (κorg) was calculated as 0.14 and 0.19 by two different methods. The number fractions of CCN predicted from the hygroscopicity data over the range of 24–359 nm are loosely consistent with those observed if the size‐ and time‐averaged g is applied to all particles (differences: −30% to +10%). This consistency improves if size‐ and time‐resolved g and g distribution are used (differences: −19% to −3%). Whereas the number fractions of CCN predicted from the composition data are greatly underestimated if organics are assumed to be insoluble (differences: −64% to −45%), they are more consistent if κorg of 0.14 or 0.19 is applied (differences: −10% to +14%). The results demonstrate the importance of the dependence of the g of particles on time and particle size and the hygroscopicity of organics for CCN number concentrations in the urban atmosphere.
Why do oceanic negative cloud‐to‐ground lightning exhibit larger peak current values?
Authors: Chronis T. , Koshak W. , McCaul E. 
Published: April 2016

AbstractThis study examines the temporal (monthly) and spatial climatology (2004–2010) of the first return stroke of the cloud‐to‐ground (CG) lightning flash peak current (Ip) across various land/water boundaries over the contiguous United States. Four regions are examined: the Gulf of Mexico (region 1), the Florida peninsula (region 2), Lake Michigan (region 3), and part of the U.S. Mid‐Atlantic (region 4). The crosss across the coastlines of regions 1, 2, and 4 show a gradual oceanward increase in the mean negative polarity CG peak current values (−Ip). This transition along the respective land/ocean boundaries is not sharp but gradual. In direct contrast with ocean, there is no consistent behavior in −Ip values as we move from land out across the fresh water of Lake Michigan (region 3). Meanwhile, the positive CG flash peak current (+Ip) values do not exhibit a consistent variation across any coastal boundary. For region 1, the −Ip values increase as we move toward the coast (southwards) especially during the wet season (June–October). This finding is in direct contrast with studies that documented winter as the season of maximum −Ip values. The zonal and seasonal variations of −Ip values across region 4 are not quite as pronounced, but the oceanic −Ip values are still larger than over the adjoining landmass. We explore in turn which up to date hypotheses pertinent to the oceanic −Ip enhancement are supported or refuted by our findings. It is concluded that the oceanic −Ip enhancement is not an artifact related to CG detection or Ip retrieval methods, nor is it likely related to the cloud top heights or CG activity. The study cannot refute the role of electrical conductivity and its contribution to CG leader attachment processes. However, given the observed “blurred transition” of the Ip values across the coastlines this paper suggests that likely the main physical mechanism is acting on the thundercloud potential. The recently suggested role of sodium chloride (NaCl) but also the role of ice crystal size (implicated herein), as possible modulators of the thundercloud potential, exhibit distinct pros and cons. Their candidacy is supported by their strong physical links to the electrostatic charging and thundercloud electric potential buildup but also by the exhibited blurred −Ip transition across the coastlines. In contrast, the suggested mechanisms cannot individually explain the observed −Ip enhancement in terms of season, NaCl concentrations, and absence of similar behavior in the respective +Ip values.
Planning, implementation, and scientific goals of the Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) field mission
Authors: Toon Owen B. , Maring Hal , Dibb Jack , Ferrare Richard , Jacob Daniel J. , Jensen Eric J. , Luo Z. Johnny , Mace Gerald G. , Pan Laura L. , Pfister Lenny , Rosenlof Karen H. , Redemann Jens , Reid Jeffrey S. , Singh Hanwant B. , Thompson Anne M. , Yokelson Robert , Minnis Patrick , Chen Gao , Jucks Kenneth W. , Pszenny Alex 
Published: April 2016

AbstractThe Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) field mission based at Ellington Field, Texas, during August and September 2013 employed the most comprehensive airborne payload to date to investigate atmospheric composition over North America. The NASA ER‐2, DC‐8, and SPEC Inc. Learjet flew 57 science flights from the surface to 20 km. The ER‐2 employed seven remote sensing instruments as a satellite surrogate and eight in situ instruments. The DC‐8 employed 23 in situ and five remote sensing instruments for radiation, chemistry, and microphysics. The Learjet used 11 instruments to explore cloud microphysics. SEAC4RS launched numerous balloons, augmented AErosol RObotic NETwork, and collaborated with many existing ground measurement sites. Flights investigating convection included close coordination of all three aircraft. Coordinated DC‐8 and ER‐2 flights investigated the optical properties of aerosols, the influence of aerosols on clouds, and the performance of new instruments for satellite measurements of clouds and aerosols. ER‐2 sorties sampled stratospheric injections of water vapor and other chemicals by local and distant convection. DC‐8 flights studied seasonally evolving chemistry in the Southeastern U.S., atmospheric chemistry with lower emissions of NOx and SO2 than in previous decades, isoprene chemistry under high and low NOx conditions at different locations, organic aerosols, air pollution near Houston and in petroleum fields, smoke from wildfires in western forests and from agricultural fires in the Mississippi Valley, and the ways in which the chemistry in the boundary layer and the upper troposphere were influenced by vertical transport in convective clouds.
The impact of cloud vertical profile on liquid water path retrieval based on the bispectral method: A theoretical study based on large‐eddy simulations of shallow marine boundary layer clouds
Authors: Miller Daniel J. , Zhang Zhibo , Ackerman Andrew S. , Platnick Steven , Baum Bryan A. 
Published: April 2016

AbstractPassive optical retrievals of cloud liquid water path (LWP), like those implemented for Moderate Resolution Imaging Spectroradiometer (MODIS), rely on cloud vertical profile assumptions to relate optical thickness (τ) and effective radius (re) retrievals to LWP. These techniques typically assume that shallow clouds are vertically homogeneous; however, an adiabatic cloud model is plausibly more realistic for shallow marine boundary layer cloud regimes. In this study a satellite retrieval simulator is used to perform MODIS‐like satellite retrievals, which in turn are compared directly to the large‐eddy simulation (LES) output. This satellite simulator creates a framework for rigorous quantification of the impact that vertical profile features have on LWP retrievals, and it accomplishes this while also avoiding sources of bias present in previous observational studies. The cloud vertical profiles from the LES are often more complex than either of the two standard assumptions, and the favored assumption was found to be sensitive to cloud regime (cumuliform/stratiform). Confirming previous studies, drizzle and cloud top entrainment of dry air are identified as physical features that bias LWP retrievals away from adiabatic and toward homogeneous assumptions. The mean bias induced by drizzle‐influenced profiles was shown to be on the order of 5–10 g/m2. In contrast, the influence of cloud top entrainment was found to be smaller by about a factor of 2. A theoretical framework is developed to explain variability in LWP retrievals by introducing modifications to the adiabatic re profile. In addition to analyzing bispectral retrievals, we also compare results with the vertical profile sensitivity of passive polarimetric retrieval techniques.
Global distribution of deep convection reaching tropopause in 1 year GPM observations
Authors: Liu Nana , Liu Chuntao 
Published: April 2016

AbstractTo characterize and quantify tropopause‐reaching deep convection, 1 year of Global Precipitation Mission (GPM) Ku band radar echoes are surveyed in relation to several reference levels derived from the ERA‐Interim reanalysis data set. Consistent with the observations of the Tropical Rainfall Measuring Mission over the tropics, the GPM has detected tropopause‐reaching deep convection dominantly over tropical land, especially over Panama and Central Africa. At middle and high latitudes, tropopause‐reaching convective storms are mainly found over land in the Northern Hemisphere during the summer. Compared to those in the tropics, convective cores at middle and high latitudes have relatively larger sizes at the tropopause, especially those over central North America. The zonal distributions of the occurrences of 15 dBZ and 20 dBZ radar echoes at the tropopause show two comparable maxima, one in the tropics and the other in northern middle‐high latitudes. This implies that the convection penetrating the tropopause at northern middle‐high latitudes is as frequent as those over the tropics. It is important to understand their role in the vertical transport of trace gases between the troposphere and the stratosphere.
Bias adjustment of satellite‐based precipitation estimation using gauge observations: A case study in Chile
Authors: Yang Zhongwen , Hsu Kuolin , Sorooshian Soroosh , Xu Xinyi , Braithwaite Dan , Verbist Koen M. J. 
Published: April 2016

AbstractSatellite‐based precipitation estimates (SPEs) are promising alternative precipitation data for climatic and hydrological applications, especially for regions where ground‐based observations are limited. However, existing satellite‐based rainfall estimations are subject to systematic biases. This study aims to adjust the biases in the Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks–Cloud Classification System (PERSIANN‐CCS) rainfall data over Chile, using gauge observations as reference. A novel bias adjustment framework, termed QM‐GW, is proposed based on the nonparametric quantile mapping approach and a Gaussian weighting interpolation scheme. The PERSIANN‐CCS precipitation estimates (daily, 0.04°×0.04°) over Chile are adjusted for the period of 2009–2014. The historical data (satellite and gauge) for 2009–2013 are used to calibrate the methodology; nonparametric cumulative distribution functions of satellite and gauge observations are estimated at every 1°×1° box region. One year (2014) of gauge data was used for validation. The results show that the biases of the PERSIANN‐CCS precipitation data are effectively reduced. The spatial patterns of adjusted satellite rainfall show high consistency to the gauge observations, with reduced root‐mean‐square errors and mean biases. The systematic biases of the PERSIANN‐CCS precipitation time series, at both monthly and daily scales, are removed. The extended validation also verifies that the proposed approach can be applied to adjust SPEs into the future, without further need for ground‐based measurements. This study serves as a valuable reference for the bias adjustment of existing SPEs using gauge observations worldwide.
Sensitivity of Amazonian TOA flux diurnal cycle composite monthly variability to choice of reanalysis
Authors: Dodson J. Brant , Taylor Patrick C. 
Published: April 2016

AbstractAmazonian deep convection experiences a strong diurnal cycle driven by the cycle in surface sensible heat flux, which contributes to a significant diurnal cycle in the top of the atmosphere (TOA) radiative flux. Even when accounting for seasonal variability, the TOA flux diurnal cycle varies significantly on the monthly timescale. Previous work shows evidence supporting a connection between variability in the convective and radiative cycles, likely modulated by variability in monthly atmospheric state (e.g., convective instability). The hypothesized relationships are further investigated with regression analysis of the radiative diurnal cycle and atmospheric state using additional meteorological variables representing convective instability and upper tropospheric humidity. The results are recalculated with three different reanalyses to test the reliability of the results. The radiative diurnal cycle sensitivity to upper tropospheric humidity is about equal in magnitude to that of convective instability. In addition, the results are recalculated with the data subdivided into the wet and dry seasons. Overall, clear‐sky radiative effects have a dominant role in radiative diurnal cycle variability during the dry season. Because of this, even in a convectively active region, the clear‐sky radiative effects must be accounted for in order to fully explain the monthly variability in diurnal cycle. Finally, while there is general agreement between the different reanalysis‐based results when examining the full data time domain (without regard to time of year), there are significant disagreements when the data are divided into wet and dry seasons. The questionable reliability of reanalysis data is a major limitation.