bluuebunny/crossref_metadata_2025_split huggingface dataset:
Global patterns of woody residence time and its influence on model simulation of aboveground biomass
Authors: Xue Bao‐Lin , Guo Qinghua , Hu Tianyu , Xiao Jingfeng , Yang Yuanhe , Wang Guoqiang , Tao Shengli , Su Yanjun , Liu Jin , Zhao Xiaoqian 
Published: April 2017

AbstractWoody residence time (τw) is an important parameter that expresses the balance between mature forest recruitment/growth and mortality. Using field data collected from the literature, this study explored the global forest τw and investigated its influence on model simulations of aboveground biomass (AGB) at a global scale. Specifically, τw was found to be related to forest age, annual temperature, and precipitation at a global scale, but its determinants were different among various plant function types. The estimated global forest τw based on the filed data showed large spatial heterogeneity, which plays an important role in model simulation of AGB by a dynamic global vegetation model (DGVM). The τw could change the resulting AGB in tenfold based on a site‐level test using the Monte Carlo method. At the global level, different parameterization schemes of the Integrated Biosphere Simulator using the estimated τw resulted in a twofold change in the AGB simulation for 2100. Our results highlight the influences of various biotic and abiotic variables on forest τw. The estimation of τw in our study may help improve the model simulations and reduce the parameter's uncertainty over the projection of future AGB in the current DGVM or Earth System Models. A clearer understanding of the responses of τw to climate change and the corresponding sophisticated description of forest growth/mortality in model structure is also needed for the improvement of carbon stock prediction in future studies.
Nitrogen dynamic in Eurasian coastal Arctic ecosystem: Insight from nitrogen isotope
Authors: Thibodeau Benoit , Bauch Dorothea , Voss Maren 
Published: April 2017

AbstractPrimary productivity is limited by the availability of nitrogen (N) in most of the coastal Arctic, as a large portion of N is released by the spring freshet and completely consumed during the following summer. Thus, understanding the fate of riverine nitrogen is critical to identify the link between dissolved nitrogen dynamic and coastal primary productivity to foresee upcoming changes in the Arctic seas, such as increase riverine discharge and permafrost thaw. Here we provide a field‐based study of nitrogen dynamic over the Laptev Sea shelf based on isotope geochemistry. We demonstrate that while most of the nitrate found under the surface freshwater layer is of remineralized origin, some of the nitrate originates from atmospheric input and was probably transported at depth by the mixing of brine‐enriched denser water during sea ice formation. Moreover, our results suggest that riverine dissolved organic nitrogen (DON) represents up to 6 times the total riverine release of nitrate and that about 62 to 76% of the DON is removed within the shelf waters. This is a crucial information regarding the near‐future impact of climate change on primary productivity in the Eurasian coastal Arctic.
A multispacecraft event study of Pc5 ultralow‐frequency waves in the magnetosphere and their external drivers
Authors: Wang Chih‐Ping , Thorne Richard , Liu Terry Z. , Hartinger Michael D. , Nagai Tsugunobu , Angelopoulos Vassilis , Wygant John R. , Breneman Aaron , Kletzing Craig , Reeves Geoffrey D. , Claudepierre Seth G. , Spence Harlan E. 
Published: April 2017

AbstractWe investigate a quiet time event of magnetospheric Pc5 ultralow‐frequency (ULF) waves and their likely external drivers using multiple spacecraft observations. Enhancements of electric and magnetic field perturbations in two narrow frequency bands, 1.5–2 mHz and 3.5–4 mHz, were observed over a large radial distance range from r ~ 5 to 11 RE. During the first half of this event, perturbations were mainly observed in the transverse components and only in the 3.5–4 mHz band. In comparison, enhancements were stronger during the second half in both transverse and compressional components and in both frequency bands. No indication of field line resonances was found for these magnetic field perturbations. Perturbations in these two bands were also observed in the magnetosheath, but not in the solar wind dynamic pressure perturbations. For the first interval, good correlations between the flow perturbations in the magnetosphere and magnetosheath and an indirect signature for Kelvin‐Helmholtz (K‐H) vortices suggest K‐H surface waves as the driver. For the second interval, good correlations are found between the magnetosheath dynamic pressure perturbations, magnetopause deformation, and magnetospheric waves, all in good correspondence to interplanetary magnetic field (IMF) discontinuities. The characteristics of these perturbations can be explained by being driven by foreshock perturbations resulting from these IMF discontinuities. This event shows that even during quiet periods, K‐H‐unstable magnetopause and ion foreshock perturbations can combine to create a highly dynamic magnetospheric ULF wave environment.
The lateral variation of Pn velocity gradient under Eurasia
Authors: Yang Xiaoning 
Published: April 2017

AbstractMantle lid P wave velocity gradient, or Pn velocity gradient, reflects the depth and lateral variations of thermal and rheological state of the uppermost mantle. Mapping the Pn velocity gradient and its lateral variation helps us gain insight into the temperature, composition, and dynamics of the uppermost mantle. In addition, because Pn velocity gradient has profound influence on Pn propagation behavior, an accurate mapping of Pn velocity gradient also improves the modeling and prediction of Pn travel times and amplitudes. In this study, I used measured Pn travel times to derive path‐specific Pn velocity gradients. I then inverted these velocity gradients for two‐dimensional (2‐D) Pn velocity‐gradient models for Eurasia based on the assumption that a path‐specific Pn velocity gradient is the mean of laterally varying Pn velocity gradients along the Pn path. Result from a Monte Carlo simulation indicates that the assumption is appropriate. The 2‐D velocity‐gradient models show that most of Eurasia has positive velocity gradients. High velocity gradients exist mainly in tectonically active regions. Most tectonically stable regions show low and more uniform velocity gradients. Strong velocity‐gradient variations occur largely along convergent plate boundaries, particularly under overriding plates.
Biases of five latent heat flux products and their impacts on mixed‐layer temperature estimates in the South China Sea
Authors: Wang Xin , Zhang Rongwang , Huang Jian , Zeng Lili , Huang Fei 
Published: April 2017

AbstractFive latent heat flux (LHF) products are evaluated based on in situ observations in the South China Sea (SCS), including the ECWMF ERA‐Interim (ERA‐I), the NCEP2, the Objectively Analyzed air‐sea Fluxes (OAFlux), the Japanese 55 year Reanalysis (JRA55), and the TropFlux data sets. The results show that there are good correlations between the LHF products and observations, ranging from 0.68 to 0.74. However, mean biases of −8 to 40 W m−2 exist in the LHF products with respect to the observations. For root‐mean‐square errors, the OAFlux data set is the closest to the observations, followed by ERA‐I and TropFlux, while the NCEP2 data set shows significant overestimation. It is found that the biases in the near‐surface‐specific humidity are most correlated with the biases in the LHF products, followed by the biases in the near‐surface wind speed, air temperature, and sea surface temperature. The biases in the LHF products have a prominent seasonal variation that is 25 W m−2 higher in boreal winter than in summer. Using the thermal equation, it is shown that the tendency errors of the mixed‐layer temperature estimated by the biases in the LHF products vary from −2.0 to 3.5°C/month in the SCS. When all of the products are averaged, the errors are reduced to a range of −0.7 to 1.5°C/month. It is noteworthy that the errors in summer are more obvious than those in winter, since a thinner mixed layer in the summer can amplify the effect of even a small bias in the LHF.
Spatial variability of upper ocean POC export in the Bay of Bengal and the Indian Ocean determined using particle‐reactive 234Th
Authors: Subha Anand S. , Rengarajan R. , Sarma V. V. S. S. , Sudheer A. K. , Bhushan R. , Singh S. K. 
Published: April 2017

AbstractThe northern Indian Ocean is globally significant for its seasonally reversing winds, upwelled nutrients, high biological production, and expanding oxygen minimum zones. The region acts as sink and source for atmospheric CO2. However, the efficiency of the biological carbon pump to sequester atmospheric CO2 and export particulate organic carbon from the surface is not well known. To quantify the upper ocean carbon export flux and to estimate the efficiency of biological carbon pump in the Bay of Bengal and the Indian Ocean, seawater profiles of total 234Th were measured from surface to 300 m depth at 13 stations from 19.9°N to 25.3°S in a transect along 87°E, during spring intermonsoon period (March–April 2014). Results showed enhanced in situ primary production in the equatorial Indian Ocean and the central Bay of Bengal and varied from 13.2 to 173.8 mmol C m−2 d−1. POC export flux in this region varied from 0 to 7.7 mmol C m−2 d−1. Though high carbon export flux was found in the equatorial region, remineralization of organic carbon in the surface and subsurface waters considerably reduced organic carbon export in the Bay of Bengal. Annually recurring anticyclonic eddies enhanced organic carbon utilization and heterotrophy. Oxygen minimum zone developed due to stratification and poor ventilation was intensified by subsurface remineralization. 234Th‐based carbon export fluxes were not comparable with empirical statistical model estimates based on primary production and temperature. Region‐specific refinement of model parameters is required to accurately predict POC export fluxes.
Role of deep crustal fluids in the genesis of intraplate earthquakes in the Kachchh region, northwestern India
Authors: Pavan Kumar G. , Mahesh P. , Nagar Mehul , Mahender E. , Kumar Virendhar , Mohan Kapil , Ravi Kumar M. 
Published: April 2017

AbstractFluids play a prominent role in the genesis of earthquakes, particularly in intraplate settings. In this study, we present evidence for a highly heterogeneous nature of electrical conductivity in the crust and uppermost mantle beneath the Kachchh rift basin of northwestern India, which is host to large, deadly intraplate earthquakes. We interpret our results of high conductive zones inferred from magnetotelluric and 3‐D local earthquake tomography investigations in terms of a fluid reservoir in the upper mantle. The South Wagad Fault (SWF) imaged as a near‐vertical north dipping low resistivity zone traversing the entire crust and an elongated south dipping conductor demarcating the North Wagad Fault (NWF) serve as conduits for fluid flow from the reservoir to the middle to lower crustal depths. Importantly, the epicentral zone of the 2001 main shock is characterized as a fluid saturated zone at the rooting of NWF onto the SWF.
The regional influence of the Arctic Oscillation and Arctic Dipole on the wintertime Arctic surface radiation budget and sea ice growth
Authors: Hegyi Bradley M. , Taylor Patrick C. 
Published: April 2017

AbstractAn analysis of 2000–2015 monthly Clouds and the Earth's Radiant Energy System‐Energy Balanced and Filled (CERES‐EBAF) and Modern‐Era Retrospective Analysis for Research and Applications, Version 2 (MERRA2) data reveals statistically significant fall and wintertime relationships between Arctic surface longwave (LW) radiative flux anomalies and the Arctic Oscillation (AO) and Arctic Dipole (AD). Signifying a substantial regional imprint, a negative AD index corresponds with positive downwelling clear‐sky LW flux anomalies (>10 W m−2) north of western Eurasia (0°E–120°E) and reduced sea ice growth in the Barents and Kara Seas in November–February. Conversely, a positive AO index coincides with negative clear‐sky LW flux anomalies and minimal sea ice growth change in October–November across the Arctic. Increased (decreased) atmospheric temperature and water vapor coincide with the largest positive (negative) clear‐sky flux anomalies. Positive surface LW cloud radiative effect anomalies also accompany the negative AD index in December–February. The results highlight a potential pathway by which Arctic atmospheric variability influences the regional surface radiation budget over areas of Arctic sea ice growth.
Large‐scale control of the lower stratosphere on variability of tropical cyclone intensity
Authors: Ferrara Madison , Groff Faith , Moon Zach , Keshavamurthy Kushal , Robeson Scott M. , Kieu Chanh 
Published: April 2017

AbstractRecent studies of tropical cyclones (TC) have suggested intricate impacts of the lower stratosphere layer (LSL) on TC development at the high‐intensity limit. This study examines the potential realization of the impacts of the LSL interannual variability on TC intensity. By minimizing the effects of sea surface temperature and outflow temperature based on the potential intensity framework, partial correlation analyses show a negative correlation between the power dissipation index (PDI) for intense TCs and the tropopause height in the northwestern Pacific basin but a weaker relationship in the north Atlantic basin. Similar analyses for the LSL stratification also reveal signals of negative correlations between the LSL stratification and PDI in both basins, corroborating recent modeling studies about the impacts of the LSL on TC development. Due to the complexity of the relationships and data limitations, however, all correlations are statistically insignificant, thus rendering the impacts of LSL on TC intensity inconclusive at present.
Stable isotopes in surface waters of the Atlantic Ocean: Indicators of ocean‐atmosphere water fluxes and oceanic mixing processes
Authors: Benetti M. , Reverdin G. , Aloisi G. , Sveinbjörnsdóttir Á. 
Published: April 2017

AbstractThe surface ocean hydrological cycle is explored based on ∼300 new δ18O and δD measurements from surface waters of the Atlantic Ocean and the Mediterranean Sea over the period 2010–2016. Our approach combines these surface observations with salinity (S) and stable isotope measurements of atmospheric water vapor. The distinct regional S‐δ distributions are used to identify different surface water masses and their horizontal advection. Moreover, based on assumptions on the δ‐S characteristics of seawater sources and the isotope composition of the evaporative (δe) and meteoric water (δMW) fluxes, the δ‐S distribution is used to indicate the relative importance of evaporation (E) and meteoric water inputs (MW). Here δe is estimated from the Craig and Gordon's equation using 120 days of measurements of the ambient air above the Atlantic Ocean collected during three cruises. To provide quantitative estimates of the E:MW ratio, we use the box model from Craig and Gordon (1965). This identifies the subtropical gyre as a region where E:MW ∼2 and the tropical ocean as a region were MW:E ∼2. Finally, we show that the δ18O‐δD distribution is better represented by a linear fit than the δ‐S relationship, even in basins governed by different hydrological processes. We interpret the δ18O‐δD distribution considering the kinetic fractionation processes associated with evaporation. In the tropical region where MW exceeds E, the δ18O‐δD distribution identifies the MW inputs from their kinetic signature, whereas in regions where E exceeds MW, the δ18O‐δD distribution traces the humidity at the sea surface.
Testing the current paradigm for space weather prediction with heliospheric imagers
Authors: Barnard Luke A. , de Koning Curt A. , Scott Christopher J. , Owens Mathew J. , Wilkinson Julia , Davies Jackie A. 
Published: April 2017

AbstractPredictions of the arrival of four coronal mass ejections (CMEs) in geospace are produced through use of three CME geometric models combined with CME drag modeling, constraining these models with the available Coronagraph and Heliospheric Imager data. The efficacy of these predications is assessed by comparison with the Space Weather Prediction Center (SWPC) numerical MHD forecasts of these same events. It is found that such a prediction technique cannot outperform the standard SWPC forecast at a statistically meaningful level. We test the Harmonic Mean, Self‐Similar Expansion, and Ellipse Evolution geometric models, and find that, for these events at least, the differences between the models are smaller than the observational errors. We present a new method of characterizing CME fronts in the Heliospheric Imager field of view, utilizing the analysis of citizen scientists working with the Solar Stormwatch project, and we demonstrate that this provides a more accurate representation of the CME front than is obtained by experts analyzing elongation time maps for the studied events. Comparison of the CME kinematics estimated independently from the STEREO‐A and STEREO‐B Heliospheric Imager data reveals inconsistencies that cannot be explained within the observational errors and model assumptions. We argue that these observations imply that the assumptions of the CME geometric models are routinely invalidated and question their utility in a space weather forecasting context. These results argue for the continuing development of more advanced techniques to better exploit the Heliospheric Imager observations for space weather forecasting.
Dosimetric validation of a magnetic resonance image gated radiotherapy system using a motion phantom and radiochromic film
Authors: Lamb James M. , Ginn John S. , O'Connell Dylan P. , Agazaryan Nzhde , Cao Minsong , Thomas David H. , Yang Yingli , Lazea Mircea , Lee Percy , Low Daniel A. 
Published: April 2017

AbstractPurposeMagnetic resonance image (MRI) guided radiotherapy enables gating directly on the target position. We present an evaluation of an MRI‐guided radiotherapy system's gating performance using an MRI‐compatible respiratory motion phantom and radiochromic film. Our evaluation is geared toward validation of our institution's clinical gating protocol which involves planning to a target volume formed by expanding 5 mm about the gross tumor volume (GTV) and gating based on a 3 mm window about the GTV.MethodsThe motion phantom consisted of a target rod containing high‐contrast target inserts which moved in the superior‐inferior direction inside a body structure containing background contrast material. The target rod was equipped with a radiochromic film insert. Treatment plans were generated for a 3 cm diameter spherical planning target volume, and delivered to the phantom at rest and in motion with and without gating. Both sinusoidal trajectories and tumor trajectories measured during MRI‐guided treatments were used. Similarity of the gated dose distribution to the planned, motion‐frozen, distribution was quantified using the gamma technique.ResultsWithout gating, gamma pass rates using 4%/3 mm criteria were 22–59% depending on motion trajectory. Using our clinical standard of repeated breath holds and a gating window of 3 mm with 10% target allowed outside the gating boundary, the gamma pass rate was 97.8% with 3%/3 mm gamma criteria. Using a 3 mm window and 10% allowed excursion, all of the patient tumor motion trajectories at actual speed resulting in at least 95% gamma pass rate at 4%/3 mm.ConclusionsOur results suggest that the device can be used to compensate respiratory motion using a 3 mm gating margin and 10% allowed excursion results in conjunction with repeated breath holds. Full clinical validation requires a comprehensive evaluation of tracking performance in actual patient images, outside the scope of this study.
Physical Therapists’ Perceptions of Telephone‐ and Internet Video–Mediated Service Models for Exercise Management of People With Osteoarthritis
Authors: Lawford Belinda J. , Bennell Kim L. , Kasza Jessica , Hinman Rana S. 
Published: April 2017

ObjectiveTo investigate physical therapists’ perceptions of, and willingness to use, telephone‐ and internet‐mediated service models for exercise therapy for people with knee and/or hip osteoarthritis.MethodsThis study used an internet‐based survey of Australian physical therapists, comprising 3 sections: 1 on demographic information and 2 with 16 positively framed perception statements about delivering exercise via telephone and video over the internet, for people with hip and/or knee osteoarthritis. Levels of agreement with each statement were evaluated. Logistic regression models were used to determine therapist characteristics influencing interest in delivering telerehabilitation.ResultsA total of 217 therapists spanning metropolitan, regional, rural, and remote Australia completed the survey. For telephone‐delivered care, there was consensus agreement that it would not violate patient privacy (81% agreed/strongly agreed) and would save patient's time (76%), but there was less than majority agreement for 10 statements. There was consensus agreement that video‐delivered care would save a patient's time (82%), be convenient for patients (80%), and not violate patient privacy (75%). Most agreed with all other perception statements about video‐delivered care, except for liking no physical contact (14%). Low confidence using internet video technologies, and inexperience with telerehabilitation, were significantly associated with reduced interest in delivering telephone and/or video‐based services.ConclusionPhysical therapists agree that telerehabilitation offers time‐saving and privacy advantages for people with osteoarthritis and perceive video‐delivered care more favorably than telephone‐delivered services. However, most do not like the lack of physical contact with either service model. These findings may inform the implementation of telerehabilitation osteoarthritis services and the training needs of clinicians involved in delivering care.