Leaf-wood separation is crucial for single-tree aboveground biomass estimation and three-dimensional reconstruction. Although the nondestructive and efficient acquisition of fine-grained, high-density point cloud data can be performed using terrestrial laser scanning technology, existing methods suffer from various drawbacks, including insufficient detection of fine branches, limited robustness to point cloud subsampling, and weak adaptability across different tree species and crown structures. A core issue lies in the over-reliance on prior values for key algorithm parameters. This article proposes an adaptive shortest path tracking for robust leaf–wood separation (ASPTS) in individual trees. First, a graph is constructed, and the shortest path backtracking is employed to extract skeleton points. Second, an improved k-nearest neighbor algorithm is proposed to adaptively optimize the number of neighboring points based on the shortest path, thereby obtaining initial wood points. Third, the feature descriptor construction for characterizing trunk and branch structures is optimized using principal component analysis by implementing an enhanced adaptive neighborhood radius selection strategy. Finally, final wood points are extracted using a region-growing approach guided by a stepwise feature thresholding scheme. A total of 22 individual trees, which represent different species, heights, and crown structures, are selected as test subjects. The results demonstrate the capability of ASPTS to make a good balance between type I and type II errors. ASPTS consistently exhibits strong fine-branch detection capability and robust performance under varying conditions, including different tree species, crown structures, and point cloud densities. ASPTS demonstrates superior performance compared to four state-of-the-art methods.
Abstract Recent record‐hot years have caused discussion over whether global warming has accelerated. Previous analysis found acceleration (i.e., increase in warming rate) has not yet reached a 95% confidence level, given natural temperature variability. We remove the estimated influence of three main natural variability factors: El Niño, volcanism, and solar variation. The resulting adjusted and thus less “noisy” data show that there has been acceleration with over 98% confidence, with faster warming over the last 10+ years than during any previous decade.
For the system noise temperature calibration of the K/Q/W triple-band cryogenic receiver on Tianma Radio Telescope (TMRT), a design of W-band eight-hole waveguide directional coupler is proposed in this paper. Based on the hole coupling principle proposed by Gian Guido Gentili, a simulation model of the eight-hole coupler is designed by ANSYS HFSS. Both simulation and experimental results demonstrate that the coupler exhibits excellent performance across the 80–110 GHz, with a coupling coefficient ranging from −25 dB to −26 dB, a directivity greater than 11 dB, and an isolation below −38 dB.
M. W. J. Hubbard, O. Hetherington, D. J. Hall
et al.
The ESA and CAS SMILE mission orbit is highly elliptical and will pass through multiple radiation environments. The Soft X-ray Imager (SXI) instrument aboard has a radiation shutter door designed to close when the surrounding radiation flux is high. The shutter door will close when passing below an altitude threshold to protect against trapped particles in the Earth’s Van Allen Belts. Therefore, two radiation environments can be approximated based on the shutter door position: open and closed. The instrument background for the CCDs (Charge-Coupled Devices) that form the focal plane array of the SXI were evaluated for the two environments. Due to the correlation of the space environment with the solar cycle, the solar minima and maxima, the background was also evaluated at these two extremes. The results demonstrated that the highest instrument background will occur during solar minima due to the main contributing source being Galactic Cosmic Rays (GCRs). It was also found that the open background was highest for solar minima and that the closed background was highest during solar maxima. This is due to the radiation shutter door acting as a scattering centre and the changes in the energy flux distribution of the GCRs between the two solar extremes.
The thermodynamic evolution of Coronal Mass Ejections (CMEs) in the inner corona (≤1.5 Rsun) is not yet completely understood. In this work, we study the evolution of thermodynamic properties of a CME core observed in the inner corona on 20 July 2017, by combining the MLSO/K-Cor white-light and the MLSO/CoMP Fe XIII 10747 Å line spectroscopic data. We also estimate the emission measure weighted temperature (TEM) of the CME core by applying the Differential Emission Measure (DEM) inversion technique on the SDO/AIA six EUV channels data and compare it with the effective temperature (Teff) obtained using Fe XIII line width measurements. We find that the Teff and TEM of the CME core show similar variation and remain almost constant as the CME propagates from ∼1.05 to 1.35 Rsun. The temperature of the CME core is of the order of million-degree kelvin, indicating that it is not associated with a prominence. Further, we estimate the electron density of this CME core using K-Cor polarized brightness (pB) data and found it decreasing by a factor of ∼3.6 as the core evolves. An interesting finding is that the temperature of the CME core remains almost constant despite expected adiabatic cooling due to the expansion of the CME core, which suggests that the CME core plasma must be heated as it propagates. We conclude that the expansion of this CME core behaves more like an isothermal than an adiabatic process.
George V. Khazanov, Christine Gabrielse, Alex Glocer
et al.
Abstract Electron heat flux is an important value for ionospheric space weather modeling networks. Utilizing the 2D array of Time History of Events and Macroscale Interactions during Substorms all‐sky‐imager (ASI) observations, Gabrielse et al. (2021, https://doi.org/10.3389/fphy.2021.744298) described a new method that estimates the auroral scale sizes of intense precipitating electron energy fluxes and their mean energies during two substorms on 16 February 2010. These parameters in combination with SuperThermal Electron Transport code were used to develop a new methodology to calculate electron thermal fluxes from data inputs in 2D during one of the substorms at 09:40:00 UT across Canada and Alaska. To test the effect of various precipitation lifetimes on electron heat flux values, boxcar averages ranging from 0 to 900 s were applied to the ASI data. These data are then combined with the newly developed kinetic simulation to determine the thermal fluxes associated with the observed diffuse and discrete precipitation.
Kaniska Mallick, Dennis Baldocchi, Andrew Jarvis
et al.
Abstract Global evaporation monitoring from Earth observation thermal infrared satellite missions is historically challenged due to the unavailability of any direct measurements of aerodynamic temperature. State‐of‐the‐art one‐source evaporation models use remotely sensed radiometric surface temperature as a substitute for the aerodynamic temperature and apply empirical corrections to accommodate for their inequality. This introduces substantial uncertainty in operational drought mapping over complex landscapes. By employing a non‐parametric model, we show that evaporation can be directly retrieved from thermal satellite data without the need of any empirical correction. Independent evaluation of evaporation in a broad spectrum of biome and aridity yielded statistically significant results when compared with eddy covariance observations. While our simplified model provides a new perspective to advance spatio‐temporal evaporation mapping from any thermal remote sensing mission, the direct retrieval of aerodynamic temperature also generates the highly required insight on the critical role of biophysical interactions in global evaporation research.
Polar Mesosphere Summer Echoes (PMSEs) are very strong radar echoes observed at altitudes near the polar summer mesopause. One of the essential properties of these radar echoes is that they can give useful diagnostic information about the physics of the scattering process. In this paper, the related characteristics of PMSEs measured with the European Incoherent SCATter Very High Frequency (EISCAT VHF) 224 MHz radar on 13–15 July 2010 are studied at different elevation angles from 78° to 90°. It is found that the PMSEs peak power and strongest PMSEs average power occur at the same elevation angles. Also interesting is that the strongest PMSEs occur at off-vertical angles when a PMSEs has a layered (multilayer) structure. And reflection may have more significant effects on PMSEs when there are double or multilayer PMSEs. Possible explanations regarding these observations are discussed.
Under the big unified framework of quantum gravitational field and quantum repulsive field, the earlier in this series of work has comprehensively expanded the general relativity and loop quantum ring gravitation theory, set up the quantum repulsive field equation corresponding to the quantum gravitational field equation, and then established the quantum hedge-unified field equation describing the interaction of quantum gravitational field and quantum repulsive field; On this basis, the quantum repulsive universe equation corresponding to the quantum gravitational universe equation has be established, thus a set of new equations describing the expansive universe model under the condition of fully considering the hedge effect of quantum gravitational field and quantum repulsion field, which can be called the expansive universe equation of quantum hedge-unified field theory, has be established. Now, let's go deep into the arche-unified physics behind the creation of the universe. Although all kinds of inflationary universe models can solve cosmological problems to a certain extent, there is no natural and reasonable analysis and explanation for all cosmological and physical consequences. For example, it is impossible to predict a large tensor-scale ratio and a relatively large spectral index run at the same time. At present, string theory, membrane theory, loop quantum gravity theory, super-gravitational holography principle and M theory, which are the theoretical basis of cosmology, are basically established by simplification in the case of breaking away from the extreme background conditions of the universe. While cosmology, which is deficient in nature, cannot provide strong support for particle physics to further advance to a wider field and a deeper level. Due to the lack of new ideas, the construction of existing theoretical models is difficult. Therefore, the existing research can only be further promoted by new astronomical observation. Unlike existing studies, we concentrate on the emergence of the big rip-rebound clusters of quantum chaotic-reticulate distribution between the outwards-push of the universe as a whole (related to pseudo-vacuum energy, Higgs field, dark energy, etc.) and the inwards-pull of the universe in local scale (related to dark matter, quantum gravity and initial gravity separated from high-dimensional supergravity, and the initial strong force separated from the grand unified force subsequently). On the one hand, we find a great impetus to make the inflation of the universe into firstly-imposed suppression, then-imposed acceleration and finally-imposed deceleration, which really explains why the universe expands at a critical rate and has the same temperature in different regions, on the other hand, we find a fundamental unit of matter and its emerging clusters evolving in the big bang, inflation and expansion of the universe accompanied by the great rip-rebound clusters of quantum chaos-reticulate distribution, which can be reduced to an arche-pulsator of neither punctiform particle nor linear string. From these two aspects, it can been seen that the evolution of the early universe is much more complicated than people originally thought. The complexity of the super inflation of the universe is mainly reflected in the big rip-rebound cluster emerging behind the gravitational disturbance (the pressure and tensor disturbance related to dark matter), the repulsive disturbance (the pressure and scalar disturbance related to dark energy), the cosmological disturbance (related to the interaction between high-dimensional supergravity and high-dimensional superrepulsion). This is a system of nonlinear stochastic differential dynamics, or a quantum statistical physical process of nonlinear nonequilibrium state. In the new research paradigms established in this series, the arche-conjugation between the high-dimensional supergravity and the high-dimensional superrepulsion, as well as between the quantum gravity and the quantum repulsion, is higher than the supersymmetry, and then becomes the core concept of the new theory. In this series, cluster-inflating configuration, spin network space and cosmic paradigm vectors are proposed, so the model of the super-inflated universe with quantum chaos-reticulate distribution emerged under the great impetus. The new model reveals that the unified inflation of the universe as a whole and the local inflation of the universe emerge together in the great impetus of the big rip-rebound cluster of quantum chaos-reticulate distribution. As a spin network model variable, the spatiotemporal mode variable is a vector composed of a series of variables, which variables include: dimension, curvature, range, expansion speed, dynamics, quantization, chaotic-reticulate distribution (inhomogeneity, concentration, fluctuation), synergy, and so on. Between particle physics and cosmology, this series of papers proposes the cosmic quantum evolution mode, the physical-sphere distributing configuration and the interaction situation variables, organizes the concepts, variables and models of these three levels, and establishes a systematic super-synergy paradigm. In this paradigm, the general Langevan equation and the general Fokker-Planck equation are established. For the quantum cosmic-sphere, a series of trend parameters are introduced to establish the dynamics of quantum gravitational mode and its master equation, and then to establish the operator distribution function and its motion equation of the action mode. For the Tachyon of upheaval in the rip-rebound-inflating of the universe, the hypothesis on the bifurcate-chaos wave of quantum is given, the quantum theory of the early photons in upheaval is set up, and the analysis on the particles of the ultrahigh energy cosmic ray from the γ ray burst is made. Finally, using Wigner-Ville distribution as a nonlinear time-frequency distribution, we establish the ultra-synergistic field equation of quantum-classic unifying action-sphere.
Abstract Foreshocks have been documented as preceding less than half of all mainshock earthquakes. These observations are difficult to reconcile with laboratory earthquake experiments and theoretical models of earthquake nucleation, which both suggest that foreshock activity should be nearly ubiquitous. Here we use a state‐of‐the‐art, high‐resolution earthquake catalog to study foreshock sequences of magnitude M4 and greater mainshocks in southern California from 2008–2017. This highly complete catalog provides a new opportunity to examine smaller magnitude precursory seismicity. Seventy‐two percent of mainshocks within this catalog are preceded by foreshock activity that is significantly elevated compared to the local background seismicity rate. Foreshock sequences vary in duration from several days to weeks, with a median of 16.6 days. The results suggest that foreshock occurrence in nature is more prevalent than previously thought and that our understanding of earthquake nucleation may improve in tandem with advances in our ability to detect small earthquakes.
Abstract More than three dozen red sprites were captured above Hurricane Matthew on the nights of 1 and 2 October 2016 as it passed to the north of Venezuela after undergoing rapid intensification. Analyses using broadband magnetic fields indicate that all of the sprites were produced by positive cloud‐to‐ground (CG) strokes located within the outer rainbands as defined by relatively cold cloud top brightness temperatures (≤194 K). Negative CG strokes with impulse charge transfers exceeding the threshold of sprite production also existed, but the timescale of the charge transfer was not sufficiently long to develop streamers. The reported observations are contrary to the finding of the Imager of Sprites/Upper Atmospheric Lightning showing that sprites are preferentially produced by negative strokes in the same geographic region. Further ground‐based observations are desired to obtain additional insights into the convective regimes associated with the dominance of negative sprites in many oceanic and coastal thunderstorms.
Abstract At 02:13 UT on 18 November 2015 when the geomagnetic dipole was tilted by −27°, the MMS spacecraft observed southward reconnection jets near the subsolar magnetopause under southward and dawnward interplanetary magnetic field conditions. Based on four‐spacecraft estimations of the magnetic field direction near the separatrix and the motion and direction of the current sheet, the location of the reconnection line was estimated to be ~1.8 RE or further northward of MMS. The Geotail spacecraft at GSM Z~1.4 RE also observed southward reconnection jets at the dawnside magnetopause 30–40 min later. The estimated reconnection line location was northward of GSM Z~2 RE. This crossing occurred when MMS observed purely southward magnetic fields in the magnetosheath. The simultaneous observations are thus consistent with the hypothesis that the dayside magnetopause reconnection line shifts from the subsolar point toward the northern (winter) hemisphere due to the effect of geomagnetic dipole tilt.
Robert C. Witter, Gary A. Carver, Richard W. Briggs
et al.
Abstract Current models used to assess earthquake and tsunami hazards are inadequate where creep dominates a subduction megathrust. Here we report geological evidence for large tsunamis, occurring on average every 300–340 years, near the source areas of the 1946 and 1957 Aleutian tsunamis. These areas bookend a postulated seismic gap over 200 km long where modern geodetic measurements indicate that the megathrust is currently creeping. At Sedanka Island, evidence for large tsunamis includes six sand sheets that blanket a lowland facing the Pacific Ocean, rise to 15 m above mean sea level, contain marine diatoms, cap terraces, adjoin evidence for scour, and date from the past 1700 years. The youngest sheet and modern drift logs found as far as 800 m inland and >18 m elevation likely record the 1957 tsunami. Previously unrecognized tsunami sources coexist with a presently creeping megathrust along this part of the Aleutian Subduction Zone.
Magnetic data provides basic information for geological and geophysical interpretation. In this study we compile recently collected (57 cruises survey) and old (published and open access) magnetic data. This compilation includes land, marine and aeromagnetic data acquired in the East Asia region. The newly acquired magnetic data are mainly concentrated mainly in the South China Sea (SCS) (especially in the northern continental shelf), the northwestern part of the West Philippine Basin (WPB), and the East China Sea. The updated magnetic dataset is gridded with a spacing of one arc-minute. The new magnetic map provides new insights into the tectonic setting of East Asia. Analysis of the compiled data reveals several regional anomaly patterns: (1) the NE-SW trending high positive magnetic anomaly zone extending from southwest Taiwan to the area about 114.5°E114.5°E and 22°N22°N is pronounced; but it is less continuous southwest of the Penghu islands. In addition, the orientation of this high linear magnetic zone changes slightly in 118.5°E,118.5°E, 22.5°N22.5°N from N60°EN60°E - N50°E.N50°E. (2) Between the Gagua Ridge (GR) and the Luzon-Okinawa Fracture Zone (LOFZ) the marine magnetic stripes of the WPB exhibit a NW-SE orientation. This suggests that the seafloor spreading could be related to the first stage of the WPB east of the LOFZ. (3) The Urdaneta and Amami plateaus are associated with high magnetization zones. These high magnetization zones extend northwestward and are subducting beneath the Ryukyu Trench.
El realce de bordes es un elemento de análisis para entender la estructura espacial de imágenes de satélite. Se presentan dos métodos para extraer los bordes de imágenes multiespectrales de satélite. Una imagen multiespectral se modela como un campo vectorial de un número de dimensiones igual al número de bandas en la imagen. En este modelo, un pixel se define como un vector formado por un número d elementos igual al número de bandas. Se aplican dos operadores vectoriales a tal campo vectorial. En nuestro primer método, extendemos la definición de gradiente. En esta extensión, se obtiene el vector diferencia del pixel central de una ventana con los pixels vecinos. Se genera entonces una imagen multiespectral donde cada pixel representa el máximo cambio en la respuesta espectral en la imagen en cualquier dirección. A esta imagen se le denomina el gradiente multiespectral. El otro método considera la generalización del Laplaciano por medio de la transformada de Fourier h-dimensional. A esta imagen se le denomina el Laplaciano multiespectral. Los operadores vectoriales realizan una extracción simultánea del contenido de bordes en las bandas espectrales de la imagen multiespectral. Nuestros métodos son libres de parámetros. Nuestros métodos trabajan para una imagen multiespectral de cualquier número de bandas. Se discuten dos ejemplos que involucran imágenes multiespectrales de satélite a dos escalas. Comparamos nuestros resultados con procedimientos de realces de bordes ampliamente empleados. La evaluación de los resultados muestra un mejor comportamiento de los métodos propuestos comparados con los operadores de bordes ampliamente usados.
doi: https://doi.org/10.1016/S0016-7169(14)71506-5
This paper relates the development of a French incoherent scatter system
which started its operations in 1965. This development took place several
years after the initial implementation of such systems in the United States,
in Peru and in the United Kingdom. The French system, owing to its bistatic
configuration and the use of continuous waves, differed from the previous
ones. These characteristics yielded signals of excellent spectral quality,
unravelling the possibility of inferring physical parameters (Doppler shift,
average ion mass) out of reach, at that time, of other systems. The
possibility of making ion drift vector measurements led to extend the system
into a quadristatic configuration. The multiple capabilities offered by the
incoherent scatter technique, notably as concerns the thermodynamical
properties of the ionosphere and of the thermosphere, led further the French
community to a project of embarking an incoherent scatter radar on board a
ship. Taking account of a project of a Scandinavian auroral zone radar and
of the considerable interest of the study of auroral zone electrodynamics,
the French community abandoned the idea of the ship and expressed an
interest in joining the Scandinavian project in conjunction with Germany and
the United Kingdom.
Kalsbeek, Feiko, Higgins, A.K., Henriksen, Niels
et al.
The geological development of Greenland spans a period of nearly 4 Ga, from Eoarchaean to the Quaternary. Greenland is the largest island on Earth with a total area of 2 166 000 km2, but only c. 410 000 km2 are exposed bedrock, the remaining part being covered by a major ice sheet (the Inland Ice) reaching over 3 km in thickness. The adjacent offshore areas underlain by continental crust have an area of c. 825 000 km2. Greenland is dominated by crystalline rocks of the Precambrian shield, which formed during a succession of Archaean and Palaeoproterozoic orogenic events and stabilised as a part of the Laurentian shield about 1600 Ma ago. The shield area can be divided into three distinct types of basement provinces: (1) Archaean rocks (3200–2600 Ma old, with local older units up to >3800Ma) that were almost unaffected by Proterozoic or later orogenic activity; (2) Archaean terrains reworked during the Palaeoproterozoic around 1900–1750 Ma ago; and (3) terrains mainly composed of juvenile Palaeoproterozoic rocks (2000–1750 Ma in age).Subsequent geological developments mainly took place along the margins of the shield. During the Proterozoic and throughout the Phanerozoic major sedimentary basins formed, notably in North and North-East Greenland, in which sedimentary successions locally reaching 18 km in thickness were deposited. Palaeozoic orogenic activity affected parts of these successions in the Ellesmerian fold belt of North Greenland and the East Greenland Caledonides; the latter also incorporates reworked Precambrian crystalline basement complexes. Late Palaeozoic and Mesozoic sedimentary basins developed along the continent–ocean margins in North, East and West Greenland and are now preserved both onshore and offshore. Their development was closely related to continental break-up with formation of rift basins. Initial rifting in East Greenland in latest Devonian to earliest Carboniferous time and succeeding phases culminated with the opening of the North Atlantic Ocean in the late Paleocene. Sea-floor spreading was accompanied by extrusion of Palaeogene (early Tertiary) plateau basalts in both central West and central–southern East Greenland. During the Quaternary Greenland was almost completely covered by ice, and the present day Inland Ice is a relic from the Pleistocene ice ages. Vast amounts of glacially eroded detritus were deposited on the continental shelves around Greenland. Mineral exploitation in Greenland has so far encompassed cryolite, lead-zinc, gold, olivine and coal. Current prospecting activities in Greenland are concentrated on gold, base metals, platinum group elements, molybdenum, iron ore, diamonds and lead-zinc. Hydrocarbon potential is confined to the major Phanerozoic sedimentary basins, notably the large basins offshore North-East and West Greenland. While reserves of oil or gas have yet to be found, geophysical data com bined with discoveries of oil seeps onshore have revealed a considerable potential for offshore oil and gas.
The combined UK/Denmark record of noctilucent cloud (NLC) observations over
the period 1964–2006 is analysed. This data set is based on visual
observations by professional and voluntary observers, with around 40
observers each year contributing reports. Evidence is found for a
significantly longer NLC season, a greater frequency of bright NLC, and a
decreased sensitivity to 5-day planetary waves, from 1973–1982, compared to
the rest of the time interval. This coincides with a period when the length
of the summer season in the stratosphere was also longer (defined by zonal
winds at 60° N, 30 hPa). At NLC heights, lower mean temperatures, and/or
higher water vapour and/or smaller planetary wave amplitudes could explain
these results. The time series of number of NLC nights each year shows a
quasi-decadal variation with good anti-correlation with the 10.7 cm solar
flux, with a lag of 13–17 months. Using multi-parameter linear fitting, it
is found that the solar-cycle and the length of summer in the stratosphere
together can explain ~40% of the year-to-year variation in NLC
numbers. However, no statistically confidant long-term trend in moderate or
bright NLC is found. For NLC displays of moderate or greater intensity, the
multi-parameter fit gives a trend of ~0.08 nights (0.35%) per year
with a statistical probability of 28% that it is zero, or as high as 0.16
nights (0.7%) per year. There is a significant increasing trend in the
number of reports of faint or very faint NLC which is inconsistent with
other observations and may be due changes in observing practices.