Temporal Slope Research Articles

Analysis of terrestrial water storage variations in South Korea using GRACE satellite and GLDAS data in Google Earth Engine

ABSTRACT With the requirement of a macroscopic approach to understanding the relationship between water resources and hydrological phenomena, such as severe droughts under climate change, this study investigates South Korea’s long-term terrestrial water storage (TWS) using GRACE satellite data. A detailed analysis of water balance in TWS, based on the GLDAS model outputs in Google Earth Engine, reveals the following results: (1) TWS anomaly shows an average decrease of −33.5 mm year−1 from 2003 to 2016; (2) spatial shifts in TWS anomaly (−1.176 to −0.424 cm) unveil regional water storage dynamics, indicating negative temporal slope changes per grid cell (−0.393 to −0.225); (3) contributions of precipitation to TWS are not always straightforward, due to runoff inefficiencies affecting water storage and groundwater; (4) accessible water, integrating surface water and groundwater linked only to the shallow layer’s soil moisture, constrains deep groundwater accounting, emphasizing the need for local groundwater surveys in further research.

Scaling relations for gamma-ray burst afterglow light curves and centroid motion independent of jet structure and dynamics

ABSTRACT Models for gamma-ray burst afterglow dynamics and synchrotron spectra are known to exhibit various scale invariances, owing to the scale-free nature of fluid dynamics and the power-law shape of synchrotron spectra. Since GRB 170817A, off-axis jet models including a lateral energy structure in the initial outflow geometry have gained in prominence. Here, we demonstrate how the scale invariance for arbitrary jet structure and dynamical stage can be expressed locally as a function of jet temporal light-curve slope. We provide afterglow flux expressions and demonstrate their use to quickly assess the physical implications of observations. We apply the scaling expressions to the Swift X-ray Telescope sample, which shows a spread in observed fluxes, binned by light-curve slope at time of observation, that increases with increasing light-curve slope. According to the scaling relations, this pattern is inconsistent with a large spread in environment densities if these were the dominant factor determining the variability of light curves. We further show how the late deep Newtonian afterglow stage remains scale-invariant but adds distinct spectral scaling regimes. Finally, we show that for given jet structure a universal curve can be constructed of the centroid offset, image size, and ellipticity (that can be measured using very large baseline interferometry) versus observer angle, in a manner independent of explosion energy and circumburst density. Our results apply to any synchrotron transient characterized by a release of energy in an external medium, including supernova remnants, kilonova afterglows, and soft gamma-repeater flares.

Prevalence of common and rare ophthalmic findings in adults attending a medical survey institute

PurposeTo examine the ophthalmic data from a large database of people attending a general medical survey institute, and to investigate ophthalmic findings of the eye and its adnexa, including differences in age and sex.MethodsRetrospective analysis including medical data of all consecutive individuals whose ophthalmic data and the prevalences of ocular pathologies were extracted from a very large database of subjects examined at a single general medical survey institute.ResultsData were derived from 184,589 visits of 3676 patients (mean age 52 years, 68% males). The prevalence of the following eye pathologies were extracted. Eyelids: blepharitis (n = 4885, 13.3%), dermatochalasis (n = 4666, 12.7%), ptosis (n = 677, 1.8%), ectropion (n = 73, 0.2%), and xanthelasma (n = 160, 0.4%). Anterior segment: pinguecula (n = 3368, 9.2%), pterygium (n = 852, 2.3%), and cataract or pseudophakia (n = 9381, 27.1%). Cataract type (percentage of all phakic patients): nuclear sclerosis (n = 8908, 24.2%), posterior subcapsular (n = 846, 2.3%), and capsular anterior (n = 781, 2.1%). Pseudophakia was recorded for 697 patients (4.6%), and posterior subcapsular opacification for 229 (0.6%) patients. Optic nerve head (ONH): peripapillary atrophy (n = 4947, 13.5%), tilted disc (n = 3344, 9.1%), temporal slope (n = 410, 1.1%), ONH notch (n = 61, 0.2%), myelinated nerve fiber layer (n = 94, 0.3%), ONH drusen (n = 37, 0.1%), optic pit (n = 3, 0.0%), and ON coloboma (n = 4, 0.0%). Most pathologies were more common in males except for ONH, and most pathologies demonstrated a higher prevalence with increasing age.ConclusionsNormal ophthalmic data and the prevalences of ocular pathologies were extracted from a very large database of subjects seen at a single medical survey institute.

Gender- and age-related differences in foveal pit morphology.

To measure the foveal pit morphology parameters and evaluate their correlations with age and sex. A retrospective cross-sectional matched comparison study in a tertiary center. Forty men and 40 age-matched women who had normal macular structures and foveal contours were enrolled. Foveal pit parameters including top width, base width, nasal width, temporal width, minimal thickness, nasal thickness, temporal thickness, nasal height, temporal height, nasal slope, and temporal slope were measured on horizontal B-scan macular optical coherence tomography and compared between men and women. Paired t-tests and Pearson's correlation analysis. The average patient age was 51.4 ± 17.5 (21-84) years. Women had a wider base width (313.1 ± 68.0 μm vs 266.8 ± 70.9 μm, P = 0.006), wider temporal width (1043.1 ± 245.6 μm vs 968.9 ± 261.0 μm, P = 0.006), thinner nasal thickness (345.6 ± 36.2 μm vs 359.7 ± 35.8 μm, P = 0.048), and flatter temporal slope (11.60 ± 2.52° vs 12.98 ± 2.68°, P = 0.016) than men. With age, the base width (r = 0.35, P = 0.025) and temporal width (r = 0.54, P = 0.0003) tended to be wider and the temporal slope was flatter (r = -0.45, P = 0.003) in women but not men. The minimal thickness tended to be thinner in the elderly group (r = 0.038, P = 0.015). Women had a significantly wider base width, wider temporal width, thinner nasal thickness, and flatter temporal slope of the foveal pit than age-matched men. The base width and temporal width were wider and the temporal slope was flatter with age in women but not men.

Optical analysis of the physiological quality of Triticum aestivum L. seeds with two vigor levels treated with Thiamethoxam

Insecticide treatment shields plants from pests. The standard tests are the ones that are most frequently used. However, some results may be unreliable or insensitive. Optical techniques such as ultra-weak photon emission and Fourier transform infrared spectroscopy can aid standard tests. In this study, two samples of wheat seeds were subjected to the accelerated aging test, resulting in two vigor levels. Every sample was divided into two groups (control and treated). The treated groups received 150 mL of Thiamethoxam for each 100 kg of seeds. The results showed that the length of the aerial part was insensitive. However, the length of the primary root showed the treated group (73% of the germination) was statistically different. The total photon counts and temporal slope profile averages associated with the ultra-weak photon emission for the treated group (73%) showed a significant difference between the control groups (73% and 94% of germination). Principal component analysis revealed differences between groups of distinct seed vigor levels. Still, it did not show differences between the groups treated and untreated. By comparing the results, optical techniques can be used to assess seed physiological quality, particularly the vigor level.

Substituting space for time: Bird responses to forest loss in space provide a general picture of responses over time.

The practice of space-for-time substitution assumes that the responses of species or communities to land-use change over space represents how they will respond to that same change over time. Space-for-time substitution is commonly used in both ecology and conservation, but whether the assumption produces reliable insights remains inconclusive. Here, we tested space-for-time substitution using data from the North American Breeding Bird Survey (BBS) and Global Forest Change (GFC) to compare the effects of landscape-scale forest cover on bird richness and abundance over time and space, for 25 space-time comparisons. Each comparison consisted of a landscape that experienced at least 20% forest loss over 19 years (temporal site) and a set of 15-19 landscapes (spatial sites) that represented the same forest cover gradient over space in 2019 as experienced over time in their corresponding temporal site. Across the 25 comparisons, the observed responses of forest and open-habitat birds to forest cover over time generally aligned with their responses to forest cover over space, but with comparatively higher variability in the magnitude and direction of effect across the 25 temporal slopes than across the 25 spatial slopes. On average, the mean differences between the spatial and temporal slopes across the 25 space-time comparisons frequently overlapped with zero, suggesting that the spatial slopes are generally informative of the temporal slopes. However, we observed high variability around these mean differences, indicating that a single spatial slope is not strongly predictive of its corresponding temporal slope. We suggest that our results may be explained by annual variability in other relevant environmental factors that combine to produce complex effects on population abundances over time that are not easily captured by snapshots in space. While not being a 1:1 proxy, measuring bird responses to changes in habitat amount in space provides an idea on how birds might be expected to eventually equilibrate to similar changes in habitat amount over time. Further, analyses such as this could be potentially used to screen for cases of regional space-time mismatches where population-limiting factors other than habitat could be playing a more important role in the population trends observed there.

Understanding the nature of the optical emission in gamma-ray bursts: analysis from TAROT, COATLI, and RATIR observations

ABSTRACT We collected the optical light-curve data of 227 gamma-ray bursts (GRBs) observed with the TAROT, COATLI, and RATIR telescopes. These consist of 133 detections and 94 upper limits. We constructed average light curves in the observer and rest frames in both X-rays (from Swift/X-Ray Telescope) and the optical. Our analysis focused on investigating the observational and intrinsic properties of GRBs. Specifically, we examined observational properties, such as the optical brightness function of the GRBs at T = 1000 s after the trigger, as well as the temporal slope of the afterglow. We also estimated the redshift distribution for the GRBs within our sample. Of the 227 GRBs analysed, we found that 116 had a measured redshift. Based on these data, we calculated a local rate of ρ0 = 0.2 Gpc−3 yr−1 for these events with z < 1. To explore the intrinsic properties of GRBs, we examined the average X-ray and optical light curves in the rest frame. We use the afterglowpy library to generate synthetic curves to constrain the parameters typical of the bright GRB jet, such as energy (〈E0〉 ∼ 1053.6 erg), opening angle (〈θcore〉 ∼ 0.2 rad), and density (〈n0〉 ∼ 10−2.1 cm−3). Furthermore, we analyse microphysical parameters, including the fraction of thermal energy in accelerated electrons (〈ϵe〉 ∼ 10−1.37) and in the magnetic field (〈ϵB〉 ∼ 10−2.26), and the power-law index of the population of non-thermal electrons (〈p〉 ∼ 2.2).

Effects of Last Glacial Maximum (LGM) sea surface temperature and sea ice extent on the isotope–temperature slope at polar ice core sites

Abstract. Stable water isotopes in polar ice cores are widely used to reconstruct past temperature variations over several orbital climatic cycles. One way to calibrate the isotope–temperature relationship is to apply the present-day spatial relationship as a surrogate for the temporal one. However, this method leads to large uncertainties because several factors like the sea surface conditions or the origin and transport of water vapor influence the isotope–temperature temporal slope. In this study, we investigate how the sea surface temperature (SST), the sea ice extent, and the strength of the Atlantic Meridional Overturning Circulation (AMOC) affect these temporal slopes in Greenland and Antarctica for Last Glacial Maximum (LGM, ∼ 21 000 years ago) to preindustrial climate change. For that, we use the isotope-enabled atmosphere climate model ECHAM6-wiso, forced with a set of sea surface boundary condition datasets based on reconstructions (e.g., GLOMAP) or MIROC 4m simulation outputs. We found that the isotope–temperature temporal slopes in East Antarctic coastal areas are mainly controlled by the sea ice extent, while the sea surface temperature cooling affects the temporal slope values inland more. On the other hand, ECHAM6-wiso simulates the impact of sea ice extent on the EPICA Dome C (EDC) and Vostok sites through the contribution of water vapor from lower latitudes. Effects of sea surface boundary condition changes on modeled isotope–temperature temporal slopes are variable in West Antarctica. This is partly due to the transport of water vapor from the Southern Ocean to this area that can dampen the influence of local temperature on the changes in the isotopic composition of precipitation and snow. In the Greenland area, the isotope–temperature temporal slopes are influenced by the sea surface temperatures near the coasts of the continent. The greater the LGM cooling off the coast of southeastern Greenland, the greater the transport of water vapor from the North Atlantic, and the larger the temporal slopes. The presence or absence of sea ice very near the coast has a large influence in Baffin Bay and the Greenland Sea and influences the slopes at some inland ice core stations. The extent of the sea ice far south slightly influences the temporal slopes in Greenland through the transport of more depleted water vapor from lower latitudes to this area. The seasonal variations of sea ice distribution, especially its retreat in summer, influence the isotopic composition of the water vapor in this region and the modeled isotope–temperature temporal slopes in the eastern part of Greenland. A stronger LGM AMOC decreases LGM-to-preindustrial isotopic anomalies in precipitation in Greenland, degrading the isotopic model–data agreement. The AMOC strength modifies the temporal slopes over inner Greenland slightly and by a little on the coasts along the Greenland Sea where the changes in surface temperature and sea ice distribution due to the AMOC strength mainly occur.

Concentration and Isotopic Composition of Atmospheric N2O Over the Last Century

AbstractTemporal changes in the magnitude and geographic distribution of different sources of nitrous oxide (N2O) are not well constrained. To better understand the dynamics of N2O in the atmosphere over the last century, we have reconstructed the mole fraction, δ15Nbulk, δ18O, and δ15NSP values of N2O from ice cores, firn air archives, and modern atmospheric samples. We have provided new firn air records from the Styx Glacier, Antarctica, and the North Greenland Eemian Ice drilling Project, and updated the firn air transport modeling of the published records. The composite reconstruction shows that the N2O growth rates were 0.26 ± 0.05, 0.15 ± 0.05 and 0.75 ± 0.01 ppb yr−1 during 1850–1930 (P1), 1931–1965 (P2) and 1966–2021 CE (P3), respectively. The temporal slope found in a linear least squares fit in δ15Nbulk and δ18O were −0.010 ± 0.025 and −0.004 ± 0.031‰ yr−1, −0.014 ± 0.013 and −0.009 ± 0.017‰ yr−1, and −0.040 ± 0.013 and −0.022 ± 0.005‰ yr−1 during P1, P2 and P3 phases, respectively. Overall, a significant long‐term trend was not observed in δ15NSP data. Two‐box model calculations using N2O mole fraction suggest that the total N2O flux (FT) at 2015 CE was 17.5 ± 1.1 TgN yr−1, where flux from the natural (FN) and anthropogenic (FA) sources were ∼60% and 40% of FT, respectively, and the contribution of FA was ∼30% of FT at 1900 CE. Estimated FA and δ15Nbulk of atmospheric N2O suggest that the anthropogenic emissions from continental regions were 12%, 25% and 76% of FA during P1, P2 and P3 phases, respectively.

Reconstruction of Past Antarctic Temperature Using Present Seasonal δ18O–Inversion Layer Temperature: Unified Slope Equations and Applications

Abstract Reconstructing the history of polar temperature from ice core water isotope (δ18O) calibration has remained a challenge in paleoclimate research, because of our incomplete understanding of various temperature–δ18O relationships. This paper resolves this classical problem in a new framework called the unified slope equations (USE), which illustrates the general relations among spatial and temporal δ18O–surface temperature slopes. The USE is applied to the Antarctica temperature change during the last deglaciation in model simulations and observations. It is shown that the comparable Antarctica-mean spatial slope with deglacial temporal slope in δ18O–surface temperature reconstruction is caused, accidentally, by the compensation responses between the δ18O–inversion layer temperature relation and the inversion layer temperature itself. Furthermore, in light of the USE, we propose that the present seasonal slope of δ18O–inversion layer temperature is an optimal paleothermometer that is more accurate and robust than the spatial slope. This optimal slope suggests the possibility of reconstructing past Antarctic temperature changes using present and future instrumental observations. Significance Statement This paper develops a new framework called the unified slope equations (USE) to provide, for the first time, a general relation among various spatial and temporal water isotope–temperature slopes. The application of the USE to Antarctic deglacial temperature change shows that the optimal paleothermometer is the seasonal slope of the inversion layer temperature.

Camel livestock in the Algerian Sahara under the context of climate change: Milk properties and livestock production practices

Camel livestock is an ancestral activity in Algeria; however, climate change has forced camel herders to modify their breeding practices to make them more sustainable. This study summarized livestock production practices, milk qualities, and the potential of camel livestock to preserve production ability under global warming. To collect data related to livestock farming practices, 10 camel herders were interviewed using a formal questionnaire. Then, 15 milk samples (9 samples of raw milk and 6 samples that had undergone heat treatment) were collected in the region of Oued Souf in southeastern Algeria to carry out the physicochemical and bacteriological analysis. From 1990 to 2021, results showed severe drought accompanied by a significant increase in the annual average maximum temperature with a temporal slope of 0.04 °C year−1 and a significant decline in annual precipitation with a temporal slope of −0.07 mm year−1. A socio-demographic survey revealed a low educational level for camel herders. They owned small herd of camels (6.84 ± 8.66 camels) in the transhumant and extensive system or > 150 heads in the nomadic and extensive system. The average daily milk production in the nomadic system was very low (<3 L/day); it was less important compared to that in the transhumant system (4–5 L/day), with an acceptable physicochemical quality but poor bacteriological quality. Given the susceptibility of the research area, we recorded that camel livestock and travel mobility were used as adaptation strategies to the effects of climate change. On the one hand, camel breed conservation programs can enhance biodiversity and a sustainable ecosystem. On the other side, a genetic improvement program that might boost productivity and profitability might be advantageous. Smallholders may benefit from this by receiving a fair and secure income and good working conditions, which could contribute significantly to social equity and local economies.

Surface Ozone‐Temperature Relationship: The Meridional Gradient Ratio Approximation

AbstractThe daily variation of ground‐level ozone (O3), a harmful pollutant, is positively correlated with air temperature (T) in many midlatitude land regions in the summer. The observed temporal regression slope between O3 and T (dO3/dT) is referred to as the “ozone‐climate change penalty” and has been proposed as a way to predict the impact of future climate warming on O3 from observations. Here, we use two chemical transport models to show that the spatial variation of dO3/dT is primarily determined by simultaneous meridional advection of O3 and T. Furthermore, the sign and magnitude of dO3/dT can be approximated by their climatological meridional gradient ratio (O3 gradient divided by T gradient). Consideration of expected changes in the meridional gradients of T and O3 due to climate change indicates that dO3/dT will likely change. Caution is needed when using the observed climate penalty to predict O3 changes.

Stress-induced analgesia: an evaluation of effects on temporal summation of pain and the role of endogenous opioid mechanisms.

Acute stress reduces responses to static evoked pain stimuli (stress-induced analgesia [SIA]). Whether SIA inhibits temporal summation of pain, a dynamic evoked pain measure indexing central sensitization, has been little studied and mechanisms were not evaluated. We tested whether acute laboratory stressors reduce temporal summation and whether endogenous opioid (EO) mechanisms contributed. Participants were 72 healthy individuals who attended 2 laboratory sessions, receiving either oral naltrexone (50 mg; opioid antagonist) or placebo (randomized, counterbalanced order). In each session, participants underwent a temporal summation protocol with evoked heat pain stimuli, once after extended rest and once after experiencing 2 acute stressors (public speaking and mental arithmetic challenge). Reduced temporal summation in the stress/pain relative to rest/pain condition indexed SIA. Analyses in the placebo condition indicated significant SIA on initial pain ratings but not temporal summation slope (index of central sensitization). This SIA effect was moderated by stress reactivity, with SIA only observed in high stress responders. Analyses comparing SIA across the drug conditions did not reveal any evidence of stress-related EO inhibition of temporal summation outcomes. Moderation analyses revealed that high, but not low, stress responders exhibited paradoxical analgesic effects of naltrexone on initial pain ratings but not temporal summation slopes. Independent of stress effects, significant EO inhibition of temporal summation slopes was observed, but only in females. Results suggest that acute stress may reduce initial ratings in temporal summation protocols via nonopioid mechanisms but does not alter the temporal summation slope commonly used to index central sensitization.

GRB 191016A: The onset of the forward shock and evidence of late energy injection

ABSTRACTWe present optical and near-infrared (NIR) photometric observations of GRB 191016 with the COATLI,DDOTI, and RATIR ground-based telescopes over the first three nights. We present the temporal evolution of the optical afterglow and describe five different stages that were not completely characterized in previous works, mainly due to scarcity of data points to accurately fit the different components of the optical emission. After the end of the prompt gamma-ray emission, we observed the afterglow rise slowly in the optical and NIR wavelengths and peak at around T + 1450 s in all filters. This was followed by an early decay, a clear plateau from T + 5000 s to T + 11 000 s, and then a regular late decay. We also present evidence of the jet break at later times, with a temporal index in good agreement with the temporal slope obtained from X-ray observations. Although many of the features observed in the optical light curves of gamma-ray bursts are usually well explained by a reverse shock (RS) or forward shock (FS), the shallowness of the optical rise and enhanced peak emission in the GRB 191016A afterglow is not well fitted by only a FS or a RS. We propose a theoretical model which considers both of these components and combines an evolving FS with a later embedded RS and a subsequent late energy injection from the central engine activity. We use this model to successfully explain the temporal evolution of the light curves and discuss its implications on the fireball properties.

Changes in hospital quality at hospitals serving black and hispanic newborns below 30 weeks' gestation.

OBJECTIVE:Examine whether the quality of Black and Hispanic serving (BHS) compared to not BHS (NBHS) NICUs has changed differentially over time.STUDY DESIGN:Infants 24-29 weeks’ gestation born at U.S. Vermont Oxford Network centers (2006-2018) were studied. We calculated adjusted hospital quality scores as the predicted probabilities of a composite in-hospital mortality and morbidities from a logistic model. We regressed hospital quality scores on birth year to estimate the linear temporal slope by BHS-serving status for hospitals within each Census division.RESULTS:Hospital quality improved similarly over time for BHS and NBHS hospitals across all divisions except West South Central where mean change in the composite score was −18.8 (95% CI: −24.1, −13.5) for NBHS and −9.3 (95% CI: −14.1, −4.6) for BHS hospitals (p-value= 0.009).CONCLUSION:Hospital quality improved similarly for BHS and NBHS hospitals across most divisions. Variation within and between divisions should be a focus for quality improvement.

Climatic versus Anthropogenic Controls of Decadal Trends (1983-2017) in Algal Blooms in Lakes and Reservoirs across China.

The proliferation of algal blooms (ABs) in lakes and reservoirs (L&Rs) poses a threat to water quality and the ecological health of aquatic communities. With global climate change, there is a concern that the frequency and geographical expansion of ABs in L&Rs could increase. China has experienced rapid economic growth and major land-use changes over the last several decades and therefore provides an excellent context for such an analysis. About 289,600 Landsat images were used to examine the spatiotemporal distribution of ABs in L&Rs (>1 km2) across China (1983-2017). Results showed significant changes in the temporal slope of the sum of normalized area (0.26), frequency (2.28), duration (6.14), and early outbreak (-3.48) of AB events in L&Rs across China. Specifically, AB-impacted water bodies expanded longitudinally, and the time range of AB observation has expanded starting in the 2000s. Spearman correlation and random forest regression analyses further indicated that, among climatic factors, wind speed and temperature contributed the most to AB expansion. Overall, anthropogenic forces have overridden the imprints of climatic factors on the temporal evolution of ABs in China's L&Rs and therefore could inform policy decisions for the management of these resources.

Nice and slow: Measuring sensitivity and visual preference toward naturalistic stimuli varying in their amplitude spectra in space and time

The 1/fα amplitude spectrum is a statistical property of natural scenes characterising a specific distribution of spatial and temporal frequencies and their associated luminance intensities. This property has been studied extensively in the spatial domain whereby sensitivity and visual preference overlap and peak for slopes within the natural range (α ≈ 1), but remains relatively less studied in the temporal domain. Here, we used a 4AFC task to measure sensitivity and a 2AFC task to measure visual preference and across a wide range of spatial (α = 0.25, 1.25, 2.25) and temporal (α = 0.25 to 2.50, step size: 0.25) slope conditions. Stimuli with a shallow temporal slope modulate rapidly (e.g. 0.25), whereas stimuli with a steep slope modulate slowly (e.g. 2.25). Interestingly, sensitivity and visual preference did not closely overlap. While the sensitivity of the visual system is highest for our stimulus with an intermediate modulation rate (1.25), which is most abundant in nature, the stimulus with the slowest modulation rate (2.25) was most preferred. It seems sensible for the visual system to be sensitive to spatiotemporal spectra that most commonly exist in nature (α ≈ 1). However, it is possible that preference might be related to what these properties signal in the natural world. Consider the cases of waves slowly vs. rapidly crashing on a beach or fast vs. slow animals. In both instances the slowest option is often the safest and preferential, suggesting that the temporal 1/fα amplitude spectrum provides additional information that may indicate preferred environmental conditions.

Rock Mass Discontinuity Extraction Method Based on Multiresolution Supervoxel Segmentation of Point Cloud

Discontinuity sets play an essential and pivotal role in the deformation monitoring and stability analysis of the rock mass, but there are still many challenges for accurately and rapidly extracting discontinuity. In this study, an extraction and characterization method of discontinuity sets based on point cloud supervoxel segmentation was proposed, which consists of four parts: 1) a multiresolution supervoxel segmentation (MRSS) algorithm was developed to classify unstructured point cloud into multiresolution facets and discrete points; 2) to extract the individual discontinuity, the single supervoxel that having spatial connectivity, similar planarity, and parallelism was clustered; 3) the orientation of individual discontinuity was calculated, respectively, based on the plane fitting parameters; and 4) for comprehensively analyzing the stability of rock mass, the improved K -means clustering algorithm is utilized to constructing the discontinuity sets that having similar orientation information. The novel method has been successfully tested on two practical cases (a rock cut and a side slope point cloud captured by the terrestrial laser scanner). A comparison with existing methods shows that the deviation of the discontinuity orientation for rock cut is less than 1°, and the time efficiency is increased by 2.6 times. In addition, the orientation variation of the seven principle discontinuity in the five temporal side slope point cloud is relatively small, the dip direction and angle are within 2° and 1°, respectively. We can conclude that the proposed method can efficiently obtain the full extent of every individual discontinuity from rock mass surface point cloud and accurately analyze their orientation information.

Moisture Source Tagging Confirming the Polar Amplification Effect in Amplifying the Temperature-δ18O Temporal Slope Since the LGM

Stable water isotopologues in paleoclimate archives ( δ 18 O ) have been widely used as an indicator to derive past climate variations. The modern observed spatial δ 18 O -temperature relation in the middle and high latitudes has been used to infer the paleotemperatures changes from ice core data. However, various studies have shown that the spatial slope is larger than the temporal slope at the drill site by a factor of 2. Physically, the different spatial and temporal slope has been suggested to result from the amplified local surface air temperature cooling in the polar region at Last Glacial Maximum (LGM), according to the slope ratio equation derived in our previous study. To explicitly confirm the “polar amplification” effect in understanding the differences between temporal and spatial isotope–temperature relations, here we use the same isotope-enabled atmospheric general circulation model with a moisture-tracing module embedded to quantitatively estimate the contributions of different sources to the precipitated heavy oxygen isotopes in the middle and high latitudes. Our results show that the major sources of δ 18 O in precipitation over middle and high latitudes are from oceans where the sea surface temperature cooling at Last Glacial Maximum (LGM) is less than −2 ° C , while the local moisture sources with a higher cooling can be also relevant for polar regions, such as north Greenland. Additionally, the neglect of the strengthened local inversion layer strength at LGM could be the main cause for the overestimated source temperature cooling by the slope ratio equation, especially for the polar regions in the Northern Hemisphere.

Gamma-Ray Burst Afterglows in the Multimessenger Era: Numerical Models and Closure Relations

Abstract Gamma-ray bursts (GRBs) associated with gravitational wave events are, and will likely continue to be, viewed at a larger inclination than GRBs without gravitational wave detections. As demonstrated by the afterglow of GW 170817A, this requires an extension of the common GRB afterglow models, which typically assume emission from an on-axis top-hat jet. We present a characterization of the afterglows arising from structured jets, providing a framework covering both successful and choked jets. We compute new closure relations for decelerating structured jets and compare them with the established relations for energy injection and refreshed shock models. The temporal slope before the jet break is found to be a simple function of the ratio between the viewing angle and effective opening angle of the jet. A numerical model to calculate synthetic light curves and spectra is publicly available as the open-source Python package afterglowpy.