Geophysical Processes Research Articles

Rockslide as a Geophysical Process of Rock Bump or Sudden Outburst of Rock and Gas

Millions of years of atmospheric, biochemical, catagenetic, metamorphic, radioactive, and other gases under the influence of rock pressure and other physico-chemical factors, were introduced into the rocks of the earth's crust and mantle year after year. During absorption, the crystal lattices of the rocks were deformed with a change in their size and shape, and the molecules of the rocks and gases formed stable chemical compounds - solid solutions [1-3]. Practice shows that under normal conditions, the reverse process - the degassing of rocks, stretches for thousands of years, which allows the crystal lattices without plastic fracture to change their sizes and shapes. But, as practice shows, at some random moment, it is possible to start the process of avalanche-like degassing of a block of rocks. After a sudden outflow of gases, the crystal lattices of the rocks must take on a natural configuration, but due to the high rate of deformation, the relaxation process cannot keep up with the increase in stress. There is a collapse of the crystal lattices with the release of energy expended by nature on their deformation and the occurrence of elastic impacts - impulses, which are known in mining practice as rock bump and sudden outburst of rocks and gas. This process is possible in the event of a chain chemical reaction in a rock mass triggered by high-energy molecules, ions, and free radicals, similar to the so-called Cold Explosion process, which was discovered in 1980 at the Institute of Chemical Physics of the USSR Academy of Sciences. The reaction mechanism of the Cold Explosion is explained by the appearance of giant deformation loads in the sample arising from the rapid cooling of the sample. During the collapse, the process of high-speed degassing plays the role of cooling, and the mechanism of the chain chemical reaction is explained by the interaction of free radicals, high-energy molecules, and other charged particles in accordance with N. Bohr's postulates. A description of the mechanism of large-scale rock-slide and the process of formation of high-energy molecules, ions, free radicals according to the principle scheme X → X • + + e¯ / Y + e¯ → Y necessary for starting a chain chemical reaction in rock massif and the physico-chemical conditions accompanying the process is devoted this article.

Screening ground risk in underground works as part of a predictive modelling approach

Tunnels and underground spaces are expensive to build, and the ground continues to present a key source of construction risk. This paper outlines the tangible benefits of an iterative and predictive ground-modelling approach to manage subsurface risk for key subsurface project stakeholders, namely owners, designers and constructors. Using a recent case study from the UK mining sector, it highlights how a well-designed and well-executed pre-construction geophysical screening process can play a vital, early role in reducing uncertainty in the ground, thereby improving the management of underground construction risk.

Fusing adjacent-track InSAR datasets to densify the temporal resolution of time-series 3-D displacement estimation over mining areas with a prior deformation model and a generalized weighting least-squares method

Interferometric synthetic aperture radar (InSAR) technology can be used to observe high spatial resolution one-dimensional (1-D) deformation along the line-of-sight direction from a single-track synthetic aperture radar (SAR) dataset. With the aid of multi-track InSAR data or a prior model, InSAR can be extended to infer 3-D deformation information, but the temporal resolution is generally limited. This paper presents an InSAR-based method to retrieve high spatio-temporal resolution 3-D displacements over mining areas (hereafter referred to as the MTI-based method). The core idea of the proposed method is to enhance the temporal resolution of the time-series 3-D displacement estimates by fusing multi-track InSAR observations and a prior model. Firstly, we retrieve high spatial resolution 3-D mining displacements from single-track InSAR 1-D deformation observations, with the assistance of the prior deformation model. By applying this approach to multi-track InSAR data over the same area, we obtain much denser 3-D mining displacement samples in time than those derived from a single-track InSAR dataset. Secondly, we propose a generalized weighted least-squares method to integrate the denser 3-D displacement samples, to solve the high temporal resolution 3-D mining displacements, in which the rank deficiency needs to be tackled. Finally, time-series 3-D mining displacements at the chronological dates of all the available multi-track SAR images are estimated. The Yungang coal mining area of China was selected to test the proposed method using two adjacent-track ALOS PALSAR-1 datasets. Compared with the single-track InSAR-derived results, the proposed method not only significantly improves the temporal resolution of the monitoring results by 42.6%, obtaining more detailed 3-D displacements, but it also provides important data support for understanding and modeling the distinctive kinematics of mining deformation and assessing mining-related geohazards. What is more, the core idea of the proposed method will be beneficial to high spatio-temporal resolution 3-D deformation estimation in other geophysical processes.

PYTAF: A Python Tool for Spatially Resampling Earth Observation Data

Earth observation data have revolutionized Earth science and significantly enhanced the ability to forecast weather, climate and natural hazards. The storage format of the majority of Earth observation data can be classified into swath, grid or point structures. Earth science studies frequently involve resampling between swath, grid and point data when combining measurements from multiple instruments, which can provide more insights into geophysical processes than using any single instrument alone. As the amount of Earth observation data increases each day, the demand for a high computational efficient tool to resample and fuse Earth observation data has never been greater. We present a software tool, called pytaf, that resamples Earth observation data stored in swath, grid or point structures using a novel block indexing algorithm. This tool is specially designed to process large scale datasets. The core functions of pytaf were implemented in C with OpenMP to enable parallel computations in a shared memory environment. A user-friendly python interface was also built. The tool has been extensively tested on supercomputers and successfully used to resample the data from five instruments on the EOS-Terra platform at a mission-wide scale.

Ion specific effects on the pressure solution of calcite single crystals

Pressure solution of carbonate-based rocks participates in many geophysical and geochemical processes occurring at or near the Earth’s surface, but fundamental knowledge is still lacking. Here, the pressure solution of calcite single crystals in water, NaCl and CaCl2 brines was investigated with an extended surface forces apparatus (SFA). This highly mechanically and thermally stable measuring technique enables to measure the deformation of two single calcite crystals undergoing pressure solution and the deformation rates with high precision as a function of load and fluid composition. The measurements in water reveal both diffusion- and dissolution-limited scenarios. Further, the pressure solution of calcite decelerates with a small concentration of NaCl compared to CaCO3-saturated solution, while the rate is promoted with an increase to 100 mM NaCl, reflecting the competition of at least two different mechanisms. In contrast, the addition of small concentrations of CaCl2 already speeds up calcite’s pressure solution. These experimental results cannot be solely explained via the increase in solubility of calcite with ionic strength, as generally proposed. Instead, they are consistent with the ion-specific effects of the interfacial composition and the distortion of the hydration structure of calcite under an applied pressure smaller than ∼25 MPa. This work advances the fundamental knowledge of pressure solution of calcite. More broadly, the novel technique developed here can be applied to other brittle and unexfoliable minerals, which notably expands the applications of SFA.

A possível fonte da seta do tempo causal em explicações geo-históricas

Meu argumento neste artigo será que a natureza, em geral, e a natureza humana, em particular, sugere que, em princípio, é possível derivar a seta do tempo causal de diversas outras setas físicas do tempo na natureza que parecem ser fenômenos unidirecionais e irreversíveis. Um argumento mais concreto será que a suposição de uma seta do tempo causal a qual geólogos recorrem em todas as explicações geohistóricas aparentemente se origina de setas do tempo geohistóricas escondidas em processos físico-geológicos unidirecionais e irreversíveis. Eu irei ilustrar esta afirmação com alguns exemplos de explicações geohistóricas na teoria da Tectônica de Placas, a maioria das quais é baseada em processos geológicos e físicos irreversíveis. Meu argumento final é mais amplo, de natureza epistemológica, segundo o qual a suposição de uma seta do tempo causal utilizada em explicações lógico-causativas no dia a dia e na ciência aparentemente é “derivada” de certa forma da seta do tempo geohistórica. Eu irei basear este argumento na relação causal e na influência mútua que ocorre na natureza entre processos geohistóricos e evolutivos em animais, incluindo processos de desenvolvimento do cérebro e da mente humana. Deste argumento reducionista, bem integrado no quadro da Epistemologia Evolutiva, é possível derivar uma grande quantidade de argumentos naturalísticos de acordo com os quais, em princípios, as leis da física geohistórica podem ser reduzidas às leis da lógica e da causalidade.

The role of Interferometric Synthetic Aperture Radar in Detecting, Mapping, Monitoring, and Modelling the Volcanic Activity of Piton de la Fournaise, La Réunion: A Review

Synthetic Aperture Radar (SAR) remote sensing plays a significant role in volcano monitoring despite the measurements’ non real-time nature. The technique’s capability of imaging the spatial extent of ground motion has especially helped to shed light on the location, shape, and dynamics of subsurface magmatic storage and transport as well as the overall state of activity of volcanoes worldwide. A variety of different deformation phenomena are observed at exceptionally active and frequently erupting volcanoes, like Piton de la Fournaise on La Réunion Island. Those offer a powerful means of investigating related geophysical source processes and offer new insights into an active volcano’s edifice architecture, stability, and eruptive behavior. Since 1998, Interferometric Synthetic Aperture Radar (InSAR) has been playing an increasingly important role in developing our present understanding of the Piton de la Fournaise volcanic system. We here collect the most significant scientific results, identify limitations, and summarize the lessons learned from exploring the rich Piton de la Fournaise SAR data archive over the past ~20 years. For instance, the technique has delivered first evidence of the previously long suspected mobility of the volcano’s unsupported eastern flank, and it is especially useful for detecting displacements related to eruptions that occur far away from the central cone, where Global Navigation Satellite System (GNSS) stations are sparse. However, superimposed deformation processes, dense vegetation along the volcano’s lower eastern flank, and turbulent atmospheric phase contributions make Piton de la Fournaise a challenging target for applying InSAR. Multitemporal InSAR approaches that have the potential to overcome some of these limitations suffer from frequent eruptions that cause the replacement of scatterers. With increasing data acquisition rates, multisensor complementarity, and advanced processing techniques that resourcefully handle large data repositories, InSAR is progressively evolving into a near-real-time, complementary, operational volcano monitoring tool. We therefore emphasize the importance of InSAR at highly active and well-monitored volcanoes such as Mount Etna, Italy, Kīlauea Volcano, Hawai’i, and Piton de la Fournaise, La Réunion.

A Synopsis of Farmland Abandonment and Its Driving Factors in Nepal

Farmland abandonment is considered as an important phenomenon for changing eco-environmental and sociocultural landscapes of mountainous rural landscape. Many studies have analyzed farmland abandonment, its driving factors, geophysical processes and consequences at landscape: however, very few have focused on mountainous developing countries such as in Nepal, which is a rapidly urbanizing country suffering from serious farmland abandonment. Therefore, our study was an attempt to (i) assess the spatiotemporal extent of farmland abandonment in Nepal, (ii) explore driving factors of farmland abandonment, and (iii) discuss on the eco-environmental and sociocultural consequences in Nepal. We reviewed various literature, documents, and national reports to obtain a dataset pertaining to the overall status of farmland use and changes along with political and socioeconomic changes, economic development processes, and policy and governance in Nepal. Our results showed that farmland abandonment is widespread; however, it is more prevalent in the hilly and mountainous regions of Nepal. A total of 9,706,000 ha, accounting for 23.9% of the total cultivated farmland in Nepal, was abandoned during the period of 2001 to 2010. The driving factors included population growth, scattered distribution of settlements, urbanization, socio-economic development, poor access to physical services, and poor implementation of agriculture development policies. Furthermore, the increasing extent of natural disasters, malaria eradication, land reform and resettlement programs, the complex system of land ownership, land fragmentation, political instabilities, and the intensification of trading in agricultural products also acted as drivers of farmland abandonment in Nepal. Farmland abandonment generates negative effects on rural societies eco-environmentally and sociologically. Abandoned plots were subjected to different forms of geomorphic damage (e.g. landslide, debris flows, gully formation, sinkhole development etc.). Farmland landscape fragmented into a group of smaller interspersed patches. Such patches were opened for grassland. Furthermore, farmland abandonment also has effects on the local population and the whole society in terms of the production of goods (e.g., foods, feed, fiber), as well as services provided by the multi-functionality (e.g. sociocultural practices, values and norms) of the agricultural landscape. Therefore, this study plays an important role in planning and implementing eco-environmental management and social development processes in Nepal.

Multifractal and multiscale entropy scaling of in-situ soil moisture time series: Study of SMOSMANIA network data, southwestern France

Soil moisture processes exhibit a strong variability in space and time due to the variability of the meteorological forcing and the spatial heterogeneity of soil properties. This study aims at providing a statistical description of soil moisture variability by analyzing data from nine in situ stations located over an West-East gradient in southwestern France (SMOSMANIA stations, distributed over an area of about 300 × 200 km). For each station, four time series of soil moisture observed at four different depths ranging from 5 cm to 30 cm are analyzed. First, possible scaling properties are investigated within the Fourier domain with the help of spectral analysis tools. Red noise-like (1/f2) scaling properties could be noticed over a fairly wide scale range (1000 h–1 h) with relatively homogeneous scaling parameters for 5 cm depth soil moistures regardless of the station. These properties are confirmed at other depths with slightly steeper spectra and more heterogeneity across stations. In a second step, multifractal analysis has been carried out on the same data. Multifractal scaling is observed over a narrower scaling range (128 h–1 h). Moment scaling functions can be parameterized within the framework of Universal Multifractals: typical parameters are C1≈0.25 and α ≈ 1.6–1.8 for surface data while both parameters are subject to strong changes (C1 increases and α decreases) as the depth increases. In a third step, Multiscale Entropy (MSE) analysis has been applied in order to analyze the dataset from an information theory point of view and to infer whether multifractal properties could have a signature on MSE estimates. The MSE function has been found to follow a power law of the aggregation time with a scaling exponent close to 0.3–0.4 for surface data. These exponents were generally close to the Hurst exponent H estimated by first-order structure functions. While it is already known that MSE should follow scaling properties in the case of monofractal signals, the results suggest that the latter property holds for natural multifractal processes. Finally, complementary numerical tests based on synthetic multifractal time series are done in order to assess the relationship between the MSE scaling exponent H′ and multifractal parameters C1, α and H. A dependency on the three multifractal parameters has been observed, yet in practice the approximation H′ ≈ H seems somewhat acceptable for processes with relatively large Hurst exponents and/or low multifractal intermittency (C1). On a more broad perspective, the existence of relationships between multifractal scaling and MSE properties could help to refine the physical interpretation of observed scaling properties in many geophysical processes.

Europa’s surface water ice crystallinity: Discrepancy between observations and thermophysical and particle flux modeling

Physical processing of Europan surface water ice by thermal relaxation, charged particle bombardment, and possible cryovolcanic activity can alter the percentage of the crystalline form of water ice compared to that of the amorphous form of water ice (the “crystallinity”) on Europa’s surface. The timescales over which amorphous water ice is thermally transformed to crystalline water ice at Europan surface temperatures (80–130 K) suggests that the water ice there should be primarily in the crystalline form, however, surface bombardment by charged particles induced by Jupiter’s magnetic field, and vapor deposition of water ice from Europan plumes, can produce amorphous water ice surface deposits on short timescales. The purpose of this investigation is to determine whether the Europan surface water ice crystallinity derived from ground-based spectroscopic measurements is in agreement with the crystallinity expected based upon temperature and radiation modeling. Using a 1D thermophysical model of Europa’s surface, we calculate an integrated full-disk crystallinity of Europa’s leading hemisphere by incorporating the thermal relaxation of amorphous to crystalline water ice and the degradation of crystalline to amorphous water ice by irradiation. Concurrently, we derive the full-disk crystallinity of Europa’s leading hemisphere using a comparison of near-infrared ground-based spectral observations from Grundy et al. (1999), Busarev et al. (2018), and the Apache Point Observatory in Sunspot, NM, with laboratory spectra from Mastrapa et al. (2008) and the Ice Spectroscopy Lab at the Jet Propulsion Laboratory. We calculate a modeled crystallinity significantly higher than crystallinities derived from ground-based observations and laboratory spectra. This discrepancy may be a result of geophysical processes, such as by vapor-deposited plume material, or it may arise from assumptions and uncertainties in the crystallinity calculations.

Interaction of mangrove surface coverage and groundwater inputs on the temperature and water level near Tulum, Quintana Roo, Mexico: Observations and modelling

We report on a series of high resolution sensor measurements from within the Yax Chen cave system near the city of Tulum, Quintana Roo, Mexico and a box model of mangrove-groundwater interactions. The sensors were positioned in the cave following a transect moving inland. Conductivity, water pressure and temperature data were collected at 30 min intervals for a span of two years. Temperature, water level, and conductivity records showed a response to large rainfall events (Hurricane Nate in October 2017 and Topical Storm Philippe in November 2017) which coincided with differences in surficial vegetation. Groundwater with areas of mangrove coverage showed an input of warm mangrove water as the water level receded to pre-rainfall levels and, the temperature effect was not observed in areas dominated by an upland forested terrain. A model of the groundwater-mangrove interaction was developed with an on-off switch for the flow of mangrove water into the groundwater system when the rainfall is sufficiently large. The model reproduces the observed timing difference in the temperature and conductivity response, and matches the field data during rainfall events. This model shows the effectiveness of simple box models in understanding a complicated geophysical processes and provides quantitative support to this previously hypothesized groundwater interaction.

3D modeling system of seismoacoustic monitoring results at the Nikolaevskoye field

The complexity of solving the problem of preventing natural and man-made disasters during intensive nature management is associated with the multifactorial nature of the conditions and causes of catastrophic events, significant variations in the properties and state of geospheres, and the lack of reliable criteria and precursors of dangerous dynamic phenomena. The modern scientific approach to solving this problem consists in modeling processes that allow to adequately describe the state of changing natural and technical systems with subsequent verification of the results of theoretical research by instrumental methods. An even greater effect is brought by the combined use of natural and theoretical methods, united by a common ideology and maximally adapted to the conditions of the problem being solved, providing continuous multivariate monitoring of geophysical fields and processes in the geospheres. In this regard, it seems very urgent to set up research work aimed at the development of scientific and methodological foundations and technical means for assessing and monitoring hazardous geomechanical processes to reduce the risk of man-made disasters during the development of mineral deposits.

New evidence of the Suess/de Vries cycle existing in historical naked-eye observations of sunspots

AbstractSolar activity affects geophysical and heliophysical processes. Long-term changes in solar activity are closely related to climate change. Solar physicists and earth science researchers need longer observations of solar activity. Current continuous observations of solar activity are only about 400 years. Some scholars have compiled naked-eye observations of sunspots from 200 BC to 1918 AD from historical documents. In this present work, the authors use the weighted wavelet transform to study the observations series. The results show the Suess - de Vries cycle with a period from 195- to 235-year existing in the discontinuous sunspot series. Meanwhile, the cycle signal changes with time. Especially, the Suess/de Vries cycle is relatively obvious from 200 BC to 400 AD, 800 AD to 1340 AD, 1610 AD to 1918 AD, with a period of about 211-year, about 195-year, and about 235-year, respectively.

METHANE IN THE SURFACE LAYER OF THE ATMOSPHERE: CURRENT CONTENT, LONG-TERM TRENDS, AND INTRA-ANNUAL VARIABILITY

The article deals with the empirical analysis of series of monthly mean concentrations of methane in the near-surface layer of the atmosphere from the global network of monitoring stations. They operate within the Global Atmosphere Watch (GAW) under the auspices of the World Meteorological Organization (WMO). The data is freely available at the World Data Center for Greenhouse Gases GAW/WMO (WDCGG) on its website https://gaw.kishou.go.jp/. The temporal coverage is from the 1980s. Data series from 69 stations are considered, of which 22 stations represent global background conditions. The rest of the stations are regional. Long-term trends in concentrations and the intra-annual (inter-monthly) deviations of monthly mean concentrations from long-term trends were studied. The multi-year trend was estimated using a series of 12-month running averages. To exclude systematic differences in methane concentrations, these series were adjusted to the series for the high-latitude Arctic station Alert (82° 30' N, 62° 21' W). The analysis showed that long-term trends are non-linear (in particular, a known pause in the growth of methane levels in 1999-2006 is observed), but are similar at most stations under consideration. Exceptions are six regional stations classified as “abnormal” in terms of methane. Possibly, this abnormality is due to the influence of certain sources of methane (anthropogenic or natural). Long-term trends at the rest of the stations just slightly differ from the average trend for the global stations. The series of intra-annual (inter-monthly) deviations of monthly mean concentrations from long-term trends for many stations (even those located at very significant distances from each other) show high correlative similarity. However, this similarity manifests itself at an optimal time shift from 5 months towards earlier dates up to 6 months towards later dates. The results of the analysis are consistent with the assumption that the intra-annual variability in methane concentration is largely driven by seasonal factors that are significantly related to latitude, such as vertical mixing in the atmosphere and destruction in the troposphere in reactions with hydroxyl. The root-mean-square values of intra-annual (inter-monthly) fluctuations in methane concentration depend significantly on latitude. In general, the higher the latitude is, the greater is the value. The maximum values are reached in the latitudinal belt within 45-50° N, and further to the North the values decrease. This feature of intra-annual fluctuations in the level of methane content may be explained, among other things, by significant inter-seasonal fluctuations in anthropogenic methane emissions occurring at the indicated latitudes in the countries with developed economies located in North America and Western Europe. The correlations of the series of intra-annual (inter-monthly) fluctuations of the monthly mean concentrations of CH4 and CO2 were estimated as rather high, about 0.8, at optimal time shifts, which is observed both at some polar stations and at tropical ones. This confirms the assumption that natural seasonal biogeochemical and geophysical processes play a significant role in the formation of intra-annual (inter-monthly) deviations of methane and carbon dioxide content in the near-surface layer from long-term trends. These processes include vertical mixing of air, CO2 absorption on the Earth’s surface, and destruction of methane in the troposphere in reactions with hydroxyl.

Model of Vertical Mixing Induced by Wind Waves

In the Navier-Stokes equations, a current is decomposed into four constituents: the mean flow, wave-orbital motion, wave-induced-turbulent and background-turbulent currents. Under certain statistical assumptions, this allows to separate the wave-induced Reynolds stress from the background one. To close the wave-induced Reynolds stress, the Prandtl approach for the wave-induced fluctuations is used, resulting in the implicit expression for the wave-induced vertical mixing function, B. Expression for B is specified, basing on the author results for the turbulent viscosity, found earlier in the frame of the three-layer concept for the air-sea interface. The explicit expression for function B is linear in both wave amplitude and friction velocity in the air. Due to exponential decay of wave amplitude, the found result means the possibility of the enhanced impact of waves on the vertical mixing and related geophysical processes, compared to the known cubic wave-amplitude dependence for B, found by Qiao et al previously.

МЕТАН В ПРИПОВЕРХНОСТНОМ СЛОЕ АТМОСФЕРЫ: СОВРЕМЕННОЕ СОДЕРЖАНИЕ, МНОГОЛЕТНИЕ ТРЕНДЫ И ВНУТРИГОДОВАЯ ИЗМЕНЧИВОСТЬ

The article is devoted to the empirical analysis of series of monthly mean concentrations of methane in the near-surface layer of the atmosphere from the global network of monitoring stations. They operate within the Global Atmosphere Watch (GAW) under the auspices of the World Meteorological Organization (WMO). The data is freely available at the World Data Center for Greenhouse Gases GAW/WMO (WDCGG) on its website https://gaw.kishou.go.jp/ . The temporal coverage is from the 1980s. Data series from 69 stations are considered, of which 22 stations represent the global background conditions. The rest of the stations are regional. Long-term trends in concentrations and intraannual (inter-monthly) deviations of mean monthly concentrations from long-term trends were studied. The multi-year trend was estimated using a series of 12-month running averages. To exclude systematic differences in methane concentrations, these series were adjusted to the series for the high-latitude Arctic station Alert (82° 30' N, 62° 21' W). The analysis showed that long-term trends are non-linear (including with a known pause in the growth of methane levels in 1999-2006), but are similar at most of the stations under consideration. Exceptions are 6 regional stations classified as ‘abnormal’ for methane. A possible cause of the abnormality is being under the influence of certain sources of methane (anthropogenic or natural). Long-term trends at the rest of the stations are just slightly differ from the average trend for global stations. The series of intra-annual (inter-monthly) deviations of mean monthly concentrations from long-term trends for many stations, even those located at very significant distances from each other, show high correlative similarity. However, it manifests itself at an optimal time shift from 5 months. towards earlier dates up to 6 months. towards later dates. The results of the analysis are consistent with the assumption that the intra-annual variability in methane concentration is largely driven by seasonal factors that are significantly related to latitude, including vertical mixing in the atmosphere and destruction in the troposphere in reactions with hydroxyl. The root-mean-square values of the intra-annual (inter-monthly) fluctuations in methane concentration significantly depend on latitude. The higher the latitude, the greater the overall value. Maximum values are reached in the latitudinal belt 45-50° N, and further, to the north, the Кузовкин В.В., Семенов С.М. 20 values decrease. This character of intra-annual fluctuations in the level of methane content may be explained, among other things, by significant inter-seasonal fluctuations in anthropogenic methane emissions at the indicated latitudes in countries with developed economies located in North America and Western Europe. The estimates of correlations of the series of intra-annual (inter-monthly) fluctuations of the average monthly concentrations of CH4 and CO2 showed that at optimal time shifts, they are rather high, about 0.8. Moreover, this is observed both at some polar stations and at tropical ones. This confirms the assumption that natural seasonal biogeochemical and geophysical processes play a significant role in the formation of intra-annual (inter-monthly) deviations of the methane and carbon dioxide content in the near-surface layer from long-term trends, namely, vertical mixing of air, CO2 absorption on the Earth's surface, destruction of methane in the troposphere in reactions with hydroxyl.

Influence of mature El Niño‐Southern Oscillation phase on seasonal precipitation and streamflow in the Yangtze River Basin, China

AbstractAs one of the most influential oceanic and atmospheric oscillations in the Earth system, El Niño‐Southern Oscillation (ENSO) has modulated numerous geophysical processes. This is particularly true for the Yangtze River Basin (YRB), which is vulnerable to Asian Monsoon and faces serious hydrological hazards. In this study, the co‐variability between lag–lead precipitation and sea surface temperature anomalies was evaluated utilizing singular value decomposition (SVD) method. Moreover, certain teleconnections between ENSO and streamflow were identified by wavelet methods. In addition, the contribution of related atmospheric variables was revealed by composite analysis. Results indicate that there are strong associations in lag–lead seasons between the wet condition (dry condition) and September–November (December–February) mature ENSO phase. Significant common power and coherence signals between the ENSO indices and the streamflow occur in the 4–8, 8–16 and 16–32 seasonal scales. Meanwhile, the activity cycle of the ENSO indices ahead of streamflow increases from the mid‐lower reaches to the source region. In addition, the Western Pacific Subtropical High is strengthened during the mature ENSO phase. Anomalous sinking motions and divergent water vapour flux occupy the YRB, reducing the precipitation and leading to the dry condition in the source region until the following March–May. On the other hand, ascending movements and abundant water vapour flux coming from northern Pacific, equatorial western Pacific and the Bay of Bengal result in the wet condition in the mid‐lower reaches.

A pore-scale numerical investigation of the effect of pore characteristics on flow properties in soils

Flow properties of soils can impact a wide range of geotechnical, agricultural, and geophysical processes. Few studies focus on the physical understanding of how pore characteristics can affect flow properties in soils. In this paper, pore network modeling is utilized to investigate intrinsic permeability, water pressure distributions, flow patterns, and critical flow paths in soils with pores varying in size, connectivity, and anisotropy. The results show that increased mean diameter, decreased standard deviation, and increased coordination number of the pores can lead to an increase in intrinsic permeability in soils. Non-uniform water pressure and flow rate distribution will more likely occur in soils with a larger pore size variability. A higher coordination number mitigates the pressure localization but slightly exacerbates non-uniform flow. With the increase in the coefficient of variation (COV) of pore diameters, the percolation path becomes more tortuous and carries more flow. When COV increases from 0 (homogeneous) to 1 (large pore size variability), the tortuosity increases from 1.00 to ∼1.71 and the flux carried by the percolation path in soils increases from 2.0% to 7.8%. Pronounced preferential flows may take place in soils with uniformly distributed pore sizes, in which the percolation path can carry as much as 9.2% of the total flux. The anisotropy in pore throat sizes also increases the flow tortuosity and the fraction of flux carried by the percolation path. The permeability anisotropy Kh/Kv increases linearly as the pore throat size anisotropy µdh/µdv increases logarithmically. These results provide insight for designing soil barriers for either uniform flows or exacerbated preferential flow for fast transport.

Optimizing performance of data processing

The industry associates data processing with the application of geophysical algorithms to seismic data, but this definition is too narrow. We should consider a broader meaning particularly in these times of increased automation, and time and cost consciousness. If processing is a method to produce information from the manipulation of data, then we should consider the framework that enables this process. A system must exist to facilitate the work. Generally, systems are a collection of computers, networks, processes and to a lesser extent people. For any given input, they create an output, which in seismic data processing can be the application of a geophysical algorithm, or it can be reordering, reducing or aggregating data. In this system, the headline grabbing geophysical process may only be a small part of the work. The underlying framework needs to be as efficient as it can be, either managing the data, enabling the geophysical process, or both.

Interannual Oscillations in Earth Rotation

AbstractAt seasonal and shorter time scales, polar motion and length‐of‐day (LOD) change are dominated by mass redistribution in the Earth climate system, including the atmosphere, oceans, and hydrosphere. Long‐term polar motion and LOD change are believed to be forced by solid Earth geophysical process, such as glacial isostatic adjustment. Decadal LOD variations are also connected to core‐mantle coupling. This study provides a comprehensive analysis of interannual oscillations in all three components of Earth rotation using accurately measured polar motion and LOD time series, and geophysical excitations computed from atmospheric, oceanic, and hydrological models over the period 1962 to 2018. Strong interannual oscillations remain in all three components after detrending and band‐pass filtering to retain variations at periods between 2 and 8 years. Polar motion Y is dominated by a 3.65‐year oscillation, plus others at periods of 2.5 and 5.9 years. Polar motion X shows a strong oscillation near 5.9 years, plus smaller variations at shorter periods. A 5.9‐year LOD variation has been recognized in earlier studies, but oscillations at periods of 2.36, 3.65, and 4.9 years are also observed. Atmosphere, ocean, and hydrosphere (AOH) sources largely account for 2.5‐ and 3.65‐year components in polar motion Y, but not for the 5.9‐year component in polar motion X and Y. The 2.36‐, 3.65‐, and 4.9‐year components in LOD can largely be accounted for by AOH sources. The 5.9‐year LOD component becomes more prominent after AOH sources have been subtracted. The presence of a 5.9‐year variation in all three components of Earth rotation suggests a source in Earth's interior, probably from the core.