bluuebunny/crossref_metadata_2025_split huggingface dataset:
Combined impacts of nitrous acid and nitryl chloride on lower-tropospheric ozone: new module development in WRF-Chem and application to China
Authors: Zhang Li , Li Qinyi , Wang Tao , Ahmadov Ravan , Zhang Qiang , Li Meng , Lv Mengyao 
Published: August 2017

Abstract. Nitrous acid (HONO) and nitryl chloride (ClNO2) – through their photolysis – can have profound effects on the nitrogen cycle and oxidation capacity of the lower troposphere. Previous numerical studies have separately considered and investigated the sources/processes of these compounds and their roles in the fate of reactive nitrogen and the production of ozone (O3), but their combined impact on the chemistry of the lower part of the troposphere has not been addressed yet. In this study, we updated the WRF-Chem model with the currently known sources and chemistry of HONO and chlorine in a new chemical mechanism (CBMZ_ReNOM), and applied it to a study of the combined effects of HONO and ClNO2 on summertime O3 in the boundary layer over China. We simulated the spatial distributions of HONO, ClNO2, and related compounds at the surface and within the lower troposphere. The results showed that the modeled HONO levels reached up to 800–1800 ppt at the surface (0–30 m) over the North China Plain (NCP), the Yangtze River Delta (YRD), and the Pearl River Delta (PRD) regions and that HONO was concentrated within a 0–200 m layer. In comparison, the simulated surface ClNO2 mixing ratio was around 800–1500 ppt over the NCP, YRD, and central China regions and was predominantly present in a 0–600 m layer. HONO enhanced daytime ROx (OH + HO2 + RO2) and O3 at the surface (0–30 m) by 2.8–4.6 ppt (28–37 %) and 2.9–6.2 ppb (6–13 %), respectively, over the three most developed regions, whereas ClNO2 increased surface O3 in the NCP and YRD regions by 2.4–3.3 ppb (or 5–6 %) and it also had a significant impact (3–6 %) on above-surface O3 within 200–500 m. The combined effects increased surface O3 by 11.5, 13.5, and 13.3 % in the NCP, YRD, and PRD regions, respectively. Over the boundary layer (0–1000 m), the HONO and ClNO2 enhanced O3 by up to 5.1 and 3.2 %, respectively, and their combined effect increased O3 by 7.1–8.9 % in the three regions. The new module noticeably improved O3 predictions at ∼ 900 monitoring stations throughout China by reducing the mean bias from −4.3 to 0.1 ppb. Our study suggests the importance of considering these reactive nitrogen species simultaneously into chemical transport models to better simulate the formation of summertime O3 in polluted regions.
Energetics and evasion dynamics of large predators and prey: pumasvs.hounds
Authors: Bryce Caleb M. , Wilmers Christopher C. , Williams Terrie M. 
Published: August 2017

Quantification of fine-scale movement, performance, and energetics of hunting by large carnivores is critical for understanding the physiological underpinnings of trophic interactions. This is particularly challenging for wide-ranging terrestrial canid and felid predators, which can each affect ecosystem structure through distinct hunting modes. To compare free-ranging pursuit and escape performance from group-hunting and solitary predators in unprecedented detail, we calibrated and deployed accelerometer-GPS collars during predator-prey chase sequences using packs of hound dogs (Canis lupus familiaris, 26 kg,n = 4–5 per chase) pursuing simultaneously instrumented solitary pumas (Puma concolor, 60 kg,n = 2). We then reconstructed chase paths, speed and turning angle profiles, and energy demands for hounds and pumas to examine performance and physiological constraints associated with cursorial and cryptic hunting modes, respectively. Interaction dynamics revealed how pumas successfully utilized terrain (e.g., fleeing up steep, wooded hillsides) as well as evasive maneuvers (e.g., jumping into trees, running in figure-8 patterns) to increase their escape distance from the overall faster hounds (avg. 2.3× faster). These adaptive strategies were essential to evasion in light of the mean 1.6× higher mass-specific energetic costs of the chase for pumas compared to hounds (mean: 0.76vs.1.29 kJ kg−1 min−1, respectively). On an instantaneous basis, escapes were more costly for pumas, requiring exercise at ≥90% of predicted $\dot {\mathrm{V }}{\mathrm{O}}_{2\mathrm{MAX}}$ and consuming as much energy per minute as approximately 5 min of active hunting. Our results demonstrate the marked investment of energy for evasion by a large, solitary carnivore and the advantage of dynamic maneuvers to postpone being overtaken by group-hunting canids.
Wind tunnel observations of weak and strong snow saltation dynamics
Authors: Paterna E. , Crivelli P. , Lehning M. 
Published: August 2017

AbstractTheoretical considerations suggest that saltation dynamics is dominated by either aerodynamic entrainment or by a combination of ejection and rebound at a given time and location. Calling these two regimes “weak” and “strong” saltation, respectively, we have investigated high‐resolution snow mass flux measurements by shadowgraphy in a cold wind tunnel to determine whether these two regimes can be experimentally reproduced. In this contribution, we first suggest that aerodynamic entrainment should lead to a negative correlation in the growth rates of horizontal versus vertical mass fluxes, while for the ejection regime, a positive correlation is plausible. Based on this criterion, we find evidence of weak and strong saltation in our data. Weak saltation is characterized by smaller peaks of horizontal mass flux; however, these peaks have a higher growth rate and therefore are typically narrow. The larger peaks are associated with strong saltation, are wider, and their frequency of occurrence increases with increasing overall saltation mass flux.
Seasonal and interannual variabilities in terminus position, glacier velocity, and surface elevation at Helheim and Kangerlussuaq Glaciers from 2008 to 2016
Authors: Kehrl L. M. , Joughin I. , Shean D. E. , Floricioiu D. , Krieger L. 
Published: August 2017

AbstractThe dynamic response of Greenland tidewater glaciers to oceanic and atmospheric change has varied both spatially and temporally. While some of this variability is likely related to regional climate signals, glacier geometry also appears to be important. In this study, we investigated the environmental and geometric controls on the seasonal and interannual evolution of Helheim and Kangerlussuaq Glaciers, Southeast Greenland, from 2008 to 2016, by combining year‐round, satellite measurements of terminus position, glacier velocity, and surface elevation. While Helheim remained relatively stable with a lightly grounded terminus over this time period, Kangerlussuaq continued to lose mass as its grounding line retreated into deeper water. By summer 2011, Kangerlussuaq's grounding line had retreated into shallower water, and the glacier had an ~5 km long floating ice tongue. We also observed seasonal variations in surface velocity and elevation at both glaciers. At Helheim, seasonal speedups and dynamic thinning occurred in the late summer when the terminus was most retreated. At Kangerlussuaq, we observed summer speedups due to surface‐melt‐induced basal lubrication and winter speedups due to ice‐shelf retreat. We suggest that Helheim and Kangerlussuaq behaved differently on a seasonal timescale due to differences in the spatial extent of floating ice near their termini, which affected iceberg‐calving behavior. Given that seasonal speedups and dynamic thinning can alter this spatial extent, these variations may be important for understanding the long‐term evolution of these and other Greenland tidewater glaciers.
Reducing the uncertainty of parameters controlling seasonal carbon and water fluxes in Chinese forests and its implication for simulated climate sensitivities
Authors: Li Yue , Yang Hui , Wang Tao , MacBean Natasha , Bacour Cédric , Ciais Philippe , Zhang Yiping , Zhou Guangsheng , Piao Shilong 
Published: August 2017

AbstractReducing parameter uncertainty of process‐based terrestrial ecosystem models (TEMs) is one of the primary targets for accurately estimating carbon budgets and predicting ecosystem responses to climate change. However, parameters in TEMs are rarely constrained by observations from Chinese forest ecosystems, which are important carbon sink over the northern hemispheric land. In this study, eddy covariance data from six forest sites in China are used to optimize parameters of the ORganizing Carbon and Hydrology In Dynamics EcosystEms TEM. The model‐data assimilation through parameter optimization largely reduces the prior model errors and improves the simulated seasonal cycle and summer diurnal cycle of net ecosystem exchange, latent heat fluxes, and gross primary production and ecosystem respiration. Climate change experiments based on the optimized model are deployed to indicate that forest net primary production (NPP) is suppressed in response to warming in the southern China but stimulated in the northeastern China. Altered precipitation has an asymmetric impact on forest NPP at sites in water‐limited regions, with the optimization‐induced reduction in response of NPP to precipitation decline being as large as 61% at a deciduous broadleaf forest site. We find that seasonal optimization alters forest carbon cycle responses to environmental change, with the parameter optimization consistently reducing the simulated positive response of heterotrophic respiration to warming. Evaluations from independent observations suggest that improving model structure still matters most for long‐term carbon stock and its changes, in particular, nutrient‐ and age‐related changes of photosynthetic rates, carbon allocation, and tree mortality.
Observations and modeling of ocean‐induced melt beneath Petermann Glacier Ice Shelf in northwestern Greenland
Authors: Cai Cilan , Rignot Eric , Menemenlis Dimitris , Nakayama Yoshihiro 
Published: August 2017

AbstractWe update observationally based estimates of subaqueous melt, Qm, beneath Petermann Glacier Ice Shelf (PGIS), Greenland, and model its sensitivity to oceanic thermal forcing, TF, and subglacial runoff, Qsg, using the Massachusetts Institute of Technology general circulation model (MITgcm), in a two‐dimensional domain, with 20 m vertical and 40 m horizontal resolution at the grounding line. We adjust the drag coefficient to match the observationally based Qm. With the inclusion of Qsg, the maximum melt rate (
) is 2 times larger in summer and 1/3 larger annually than in winter.
increases above linear with TF and below linear with Qsg. We estimate that
increased by 24% (+8.1 m/yr) beneath PGIS from the 1990s to the 2000s from a 0.21°C warming in ocean temperature and a doubling in Qsg, hence contributing to its thinning. If the PGIS is removed, we estimate that the modeled melt rate near the grounding line will increase 13–16 times.
Anticyclonic precession of a plume in a rotating environment
Authors: Frank D. , Landel J. R. , Dalziel S. B. , Linden P. F. 
Published: August 2017

AbstractMotivated by potential effects of the Earth's rotation on the Deepwater Horizon oil plume, we conducted laboratory experiments on saltwater point plumes in a homogeneous rotating environment across a wide range of Rossby numbers 0.02≤Ro≤1.3. We report a striking physical instability in the plume dynamics near the source: after approximately one rotation period, the plume tilts laterally and starts to precess anticyclonically. The mean precession frequency
scales linearly with the rotation rate Ω as
. We find no evidence of a critical Rossby number above which precession ceases. We infer that a conventionally defined Rossby number is not an appropriate parameter when the plume is maintained over a long time: provided Ω ≠ 0, rotation is always important to the dynamics. This indicates that precession may occur in persistent oceanic or atmospheric plumes even at low latitudes.
Marine radiocarbon reservoir age simulations for the past 50,000 years
Authors: Butzin M. , Köhler P. , Lohmann G. 
Published: August 2017

AbstractRadiocarbon (14C) dating calibration for the last glacial period largely relies on cross‐dated marine 14C records. However, marine reservoirs are isotopically depleted with respect to the atmosphere and therefore have to be corrected by the Marine Radiocarbon Ages of surface waters (MRAs), whose temporal variabilities are largely unknown. Here we present simulations of the spatial and temporal variability in MRAs using a three‐dimensional ocean circulation model covering the past 50,000 years. Our simulations are compared to reconstructions of past surface ocean Δ14C. Running the model with different climatic boundary conditions, we find that low‐latitude to midlatitude MRAs have varied between 400 and 1200 14C years, with values of about 780 14C years at the Last Glacial Maximum. Reservoir ages exceeding 2000 14C years are simulated in the polar oceans. Our simulation results can be used as first‐order approximation of the MRA variability in future radiocarbon calibration efforts.
Do weak global stresses synchronize earthquakes?
Authors: Bendick R. , Bilham R. 
Published: August 2017

AbstractInsofar as slip in an earthquake is related to the strain accumulated near a fault since a previous earthquake, and this process repeats many times, the earthquake cycle approximates an autonomous oscillator. Its asymmetric slow accumulation of strain and rapid release is quite unlike the harmonic motion of a pendulum and need not be time predictable, but still resembles a class of repeating systems known as integrate‐and‐fire oscillators, whose behavior has been shown to demonstrate a remarkable ability to synchronize to either external or self‐organized forcing. Given sufficient time and even very weak physical coupling, the phases of sets of such oscillators, with similar though not necessarily identical period, approach each other. Topological and time series analyses presented here demonstrate that earthquakes worldwide show evidence of such synchronization. Though numerous studies demonstrate that the composite temporal distribution of major earthquakes in the instrumental record is indistinguishable from random, the additional consideration of event renewal interval serves to identify earthquake groupings suggestive of synchronization that are absent in synthetic catalogs. We envisage the weak forces responsible for clustering originate from lithospheric strain induced by seismicity itself, by finite strains over teleseismic distances, or by other sources of lithospheric loading such as Earth's variable rotation. For example, quasi‐periodic maxima in rotational deceleration are accompanied by increased global seismicity at multidecadal intervals.
Estimating morning change in land surface temperature from MODIS day/night observations: Applications for surface energy balance modeling
Authors: Hain Christopher R. , Anderson Martha C. 
Published: August 2017

AbstractObservations of land surface temperature (LST) are crucial for the monitoring of surface energy fluxes from satellite. Methods that require high temporal resolution LST observations (e.g., from geostationary orbit) can be difficult to apply globally because several geostationary sensors are required to attain near‐global coverage (60°N to 60°S). While these LST observations are available from polar‐orbiting sensors, providing global coverage at higher spatial resolutions, the temporal sampling (twice daily observations) can pose significant limitations. For example, the Atmosphere Land Exchange Inverse (ALEXI) surface energy balance model, used for monitoring evapotranspiration and drought, requires an observation of the morning change in LST—a quantity not directly observable from polar‐orbiting sensors. Therefore, we have developed and evaluated a data‐mining approach to estimate the midmorning rise in LST from a single sensor (two observations per day) of LST from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor on the Aqua platform. In general, the data‐mining approach produced estimates with low relative error (5 to 10%) and statistically significant correlations when compared against geostationary observations. This approach will facilitate global, near‐real‐time applications of ALEXI at higher spatial and temporal coverage from a single sensor than currently achievable with current geostationary data sets.
Numerical simulations of a sounding rocket in ionospheric plasma: Effects of magnetic field on the wake formation and rocket potential
Authors: Darian D. , Marholm S. , Paulsson J. J. P. , Miyake Y. , Usui H. , Mortensen M. , Miloch W. J. 
Published: August 2017

AbstractThe charging of a sounding rocket in subsonic and supersonic plasma flows with external magnetic field is studied with numericalparticle‐in‐cell(PIC) simulations. A weakly magnetized plasma regime is considered that corresponds to the ionosphericF2layer, with electrons being strongly magnetized, while the magnetization of ions is weak. It is demonstrated that the magnetic field orientation influences the floating potential of the rocket and that with increasing angle between the rocket axis and the magnetic field direction the rocket potential becomes less negative. External magnetic field gives rise to asymmetric wake downstream of the rocket. The simulated wake in the potential and density may extend as far as 30 electron Debye lengths; thus, it is important to account for these plasma perturbations when analyzing in situ measurements. A qualitative agreement between simulation results and the actual measurements with a sounding rocket is also shown.
Magnetospheric ion influence at the dayside magnetopause
Authors: Fuselier S. A. , Burch J. L. , Mukherjee J. , Genestreti K. J. , Vines S. K. , Gomez R. , Goldstein J. , Trattner K. J. , Petrinec S. M. , Lavraud B. , Strangeway R. J. 
Published: August 2017

AbstractMagnetospheric ions have the potential to affect magnetic reconnection at the magnetopause. The results of a survey of magnetospheric ions near the magnetopause are reported here. Composition measurements from the Magnetospheric Multiscale (MMS) mission are used to determine the total mass density of all magnetospheric ions and distinguish two populations of magnetospheric ions: the warm plasma cloak and the plasmaspheric drainage plume. The warm plasma cloak can contain substantial O+, and the plasmaspheric plume can contain substantial He+. The results of the survey show that, for nominal magnetospheric activity, the warm plasma cloak and plasmaspheric plume will reduce the normalized reconnection rate at the magnetopause by greater than 20% only a few percent of the time.
Regional gravity field recovery using the GOCE gravity gradient tensor and heterogeneous gravimetry and altimetry data
Authors: Wu Yihao , Zhou Hao , Zhong Bo , Luo Zhicai 
Published: August 2017

AbstractA regional approach using Poisson wavelets is applied for gravity field recovery using the GOCE (Gravity Field and Steady‐State Ocean Circulation Explorer) gravity gradient tensor, heterogeneous gravimetry data, and altimetry measurements. The added value to the regional model introduced by GOCE data is validated and quantified. The performances of the solutions modeled with different diagonal components of GOCE data and their combinations are investigated. Numerical experiments in a region in Europe show that the effects introduced by GOCE data demonstrate long‐wavelength patterns on the centimeter scale in terms of quasi‐geoid heights, which may allow reducing the remaining long‐wavelength errors in ground‐based data, and improve the regional model. The accuracy of the gravimetric quasi‐geoid computed with a combination of three diagonal components is improved by 0.6 cm (0.5 cm) in the Netherlands (Belgium) compared to that derived from gravimetry and altimetry data alone, when GOCO05s is used as the reference model. Moreover, the added value from GOCE data reduces the mean values of the misfit between the gravimetric solution and GPS/leveling data. Performances of different components and their combinations are not identical, and the solution with vertical gradients is best when a single component is used. The incorporation of multiple components shows further improvements, and the combination of three components best fits the local GPS/leveling data. Further comparison shows that our solution is the highest quality and may be substituted for existing models for engineering purposes and geophysical investigations over the target area.
The induced earthquake sequence related to the St. Gallen deep geothermal project (Switzerland): Fault reactivation and fluid interactions imaged by microseismicity
Authors: Diehl T. , Kraft T. , Kissling E. , Wiemer S. 
Published: August 2017

AbstractIn July 2013, a sequence of more than 340 earthquakes was induced by reservoir stimulations and well‐control procedures following a gas kick at a deep geothermal drilling project close to the city of St. Gallen, Switzerland. The sequence culminated in anML3.5 earthquake, which was felt within 10–15 km from the epicenter. High‐quality earthquake locations and 3‐D reflection seismic data acquired in the St. Gallen project provide a unique data set, which allows high‐resolution studies of earthquake triggering related to the injection of fluids into macroscopic fault zones. In this study, we present a high‐precision earthquake catalog of the induced sequence. Absolute locations are constrained by a coupled hypocenter‐velocity inversion, and subsequent double‐difference relocations image the geometry of theML3.5 rupture and resolve the spatiotemporal evolution of seismicity. A joint interpretation of earthquake and seismic data shows that the majority of the seismicity occurred in the pre‐Mesozoic basement, hundreds of meters below the borehole and the targeted Mesozoic sequence. We propose a hydraulic connectivity between the reactivated fault and the borehole, likely through faults mapped by seismic data. Despite the excellent quality of the seismic data, the association of seismicity with mapped faults remains ambiguous. In summary, our results document that the actual hydraulic properties of a fault system and hydraulic connections between its fault segments are complex and may not be predictable upfront. Incomplete knowledge of fault structures and stress heterogeneities within highly complex fault systems additionally challenge the degree of predictability of induced seismicity related to underground fluid injections.