Located at the meeting point between the Red Sea Ridge, the East African Rift and the Aden Ridge, the Afar Depression is characterized by contrasting modes of deformation with focused extension across recently activated magmatic segments and broadly distributed faults. InSAR data spanning over two decades reveal stable and evolving patterns in the deformation field of Central Afar, including (1) a 120 km-wide belt of horizontal extension, extending from west to east between the Manda-Hararo and Asal-Ghoubbet rifts and accommodating ~12 mm/yr of the Arabia-Somalia plate motion, (2) broad zones of subsidence aligned with the axial volcanic ridges marking the major diverging segments propagating into Afar, (3) accelerated opening and uplift across the Manda-Hararo Rift subsequent to the 2005-2010 diking sequence, and (4) a series of four micro-faulting events, which occurred between 2001 and 2005 on an alignment of north-northeast trending rifts between the Afdera and Gad Elu volcanoes. These observations suggest that different modes of deformation take place in the shallow and deeper parts of the crust, which are mechanically decoupled. Major magmatic segments steadily opening into the deep part of the crust between diking episodes, produce focused extension and plate thinning at intermediate depth, resulting in localized subsidence along axial ridges. The horizontal diverging movement across the segments is transformed by creep in a detachment fault at the base of the brittle crust, which deforms by distributed faulting. Episodic emplacements of dikes above deep-seated diverging segments compensate for inter-diking subsidence, also accommodating extension in the shallow crust.

The paper presents two newly geophysical effects from Volcano activity not yet described that aids to explain a Zero Energy occurred at Tenerife (Canary Islands) on September 29, 2019 . This day at 13 hours 11 minutes 35.508 seconds an initial spiking signal was recorded at the Magnetotelluric station installed within the Teide Volcanic Caldera in Las Canadas. It is a well-exposed caldera depression in which the active \Teide-Pico Viejo” complex stands. The first spike was followed by two other signals at 13:11:36.914 and 13:11:38. The signals were getting more powerful from the first, weakest, to the last, the strongest one. Same day at 13:11:47.320 a first failure occurred in one of the power distributions bars of the Granadilla Power Plant located at 26 Km from the Magnetotelluric station followed by a second disastrous failure of the second bar at 13:11:48:406. From these signals and events, we can see a strong correlation between the second and third signals in the magnetotelluric instrument and the events that burn out the bars at the distribution centre of the power plant. We have in both cases a time difference of 1.086 seconds. In the present paper we will present an explanation of these events based on; i) a piezoelectric effect caused by a thermal instability deep in the volcano structure that generated an extremely high electrical potential that was initially recorded in the surface (point approximate in the vertical) by the magnetotelluric instruments; ii) and later on via a phenomena that we named as an Earth Lightning the knocking of the power plant’s distribution park.

Earth’s atmosphere underwent an irreversible, and geologically sudden, change approximately 2.5 billion years ago from oxygen free, to oxygenated, called the Great Oxidation Event (GOE). This change was driven by the evolution of a new form of photosynthesis which produced molecular oxygen as a byproduct. The group of bacteria in which this evolved, Cyanobacteria, are the only organisms to independently harness this form of photosynthesis. While we know that by the time of the GOE, Cyanobacteria were present, we do not know if they were present before the GOE. It has been proposed that Cyanobacteria were restricted to freshwater environments for hundreds of millions of years before the GOE, and only when they were able to inhabit the oceans did the GOE occur. We address this hypothesis by surveying the literature to understand how modern cyanobacteria respond to changes in salinity, as well as running a 1000 generation evolution experiment. We find evidence that just because a cyanobacterial species is found in freshwater does not mean it cannot live in marine salinities, and vice versa. Additionally, we find that prolonged exposure to a different salinity does not result in loss of ability to grow in the ancestral salinity.

The Northern Hemisphere (NH) polar winter stratosphere of 2019/2020 featured an exceptionally strong and cold stratospheric polar vortex. Wave activity from the troposphere during December-February was unusually low, which allowed the polar vortex to remain relatively undisturbed. Several transient wave pulses nonetheless served to help create a reflective configuration of the stratospheric circulation by disturbing the vortex in the upper stratosphere. Subsequently, multiple downward wave coupling events took place, which aided in dynamically cooling and strengthening the polar vortex. The persistent strength of the stratospheric polar vortex was accompanied by an unprecedentedly positive phase of the Arctic Oscillation in the troposphere during January-March, which was consistent with large portions of observed surface temperature and precipitation anomalies during the season. Similarly, conditions within the strong polar vortex were ripe for allowing substantial ozone loss: The undisturbed vortex was a strong transport barrier, and temperatures were low enough to form polar stratospheric clouds for over four months into late March. Total column ozone amounts in the NH polar cap decreased, and were the lowest ever observed in the February-April period. The unique confluence of conditions and multiple broken records makes the 2019/2020 winter and early spring a particularly extreme example of two-way coupling between the troposphere and stratosphere.

Dust emitted from North Africa is transported over long distances and has a strong impact on large areas over the North Tropical Atlantic Ocean. Sea salt emitted by the sea surface is the second source of essential elements transported in the atmosphere and plays a major role in the cycles of alkaline-earth metals in the ecosystems of tropical North Atlantic Islands. The total atmospheric deposition fluxes were continuously sampled on a weekly basis in Guadeloupe, Lesser Antilles, from March 2015 to August 2018 (41 months). Elemental deposition fluxes including Al, Ca, K, Mg, Fe, Na, P, S, and Zn were measured for all samples in order to provide the first long time series of atmospheric elemental deposition fluxes over the Lesser Antilles region. It is shown that: (i) the three sources of atmospheric deposits in Guadeloupe for the presented elements are sea salt (for K, Ca, Mg, Na, S), long-range transported Saharan dust (for Al, Ca, K, Fe), and biogenic particles (for P and Zn); (ii) the average deposition mass fluxes of sea salt and Saharan dust are 16.7 g.m-2.year-1 and 10.6 g.m-2.year-1, respectively, without noticeable inter-annual variations; (iii) a pronounced seasonality is found for the Saharan dust deposition, for which maximum flux values are observed between June and July each year and 85% of the annual deposition flux occurs between April and September; (iv) the deposition flux of sea salt is strongly correlated to local wind speed, without seasonality.

We present an assessment of the impacts on atmospheric composition and radiative forcing of short-lived pollutants following worldwide decrease in anthropogenic activity and emissions comparable to what has occurred in response to the COVID-19 pandemic, using the global composition-climate model UKCA. Changes in emissions reduce tropospheric hydroxyl radical and ozone burdens, increasing methane lifetime. Reduced SO emissions and oxidising capacity lead to a decrease in the sulphate aerosol burden and increase in aerosol particle size, with accompanying reductions to cloud droplet number concentration. However, large reductions in black carbon emissions increase the albedo of aerosols. Overall, the changes in ozone and aerosol direct effects (neglecting aerosol-cloud interactions) result in an instantaneous radiative forcing of -31 to -74 mWm. Upon cessation of emission reductions the short-lived climate forcers rapidly return to pre-COVID levels, meaning these changes are unlikely to have lasting impacts on climate assuming emissions return to pre-intervention levels.

We present a test particle study of perturbations of a weakly relativistic electron distribution interacting with a rising-tone lower band chorus emission. Trajectories of interacting electrons are traced back in time from the equator to reconstruct the perturbed velocity distribution. The wave field is precalculated from a model based on the nonlinear growth theory and features a realistic subpacket structure. The perturbed distribution reveals a series of stripes of increased and decreased phase space density. This perturbation is associated with the electromagnetic hole structure which exists along the resonance velocity curve of each subpacket. Time-averaging of the final distribution shows that rising-tone lower band chorus emissions produce a sharp decrease in density at low parallel velocities, which might be detectable by spacecraft particle instruments.

The increasing frequency of very high temperatures driven by global warming has motivated growing interest in how the probability distribution of summertime temperatures will evolve in the future. Climate models predict increasing temperature variance in global warming simulations, but given their biased representations of historical temperature variability, it is important to use simple models to evaluate and understand these predictions. In this study we show that the projections of increasing temperature variance are indeed credible and are driven primarily by the magnitude of local warming. A simple analytic theory based on the surface energy and water budgets reproduces the increased midlatitude summertime temperature variance shown by state of the art climate models using only the local change in summertime mean temperature and relative humidity. The relative contributions of local warming and relative humidity changes to the increases in summertime temperature variance are roughly equal.

The linearity of the global-mean outgoing longwave radiation (OLR) with surface temperature has important implications for climate sensitivity. Global climate models robustly produce a 1.9 W/m2/K of global-mean longwave clear-sky (LWCS) feedback. This number is consistent with idealized single-column atmospheric models. However, there is considerable spatial variation in the LWCS feedback including negative values over tropical oceans known as the “super-greenhouse effect” which is compensated by larger values in the subtropics/extratropics. Therefore it is unclear how the idealized model results are relevant for the global-mean LWCS feedback in comprehensive climate models. Here we show with a simple analytical theory and model output that the compensation of this spatial variability to produce a robust global-mean feedback can be explained by two facts: 1) when conditioned upon free-tropospheric column relative humidity (RH), the LWCS feedback is independent of RH, and 2) the global histogram of column RH is largely invariant under warming.

Each year the PRSN detects ~4,000 earthquakes within and around Puerto Rico, the Virgin Islands and the Eastern Dominican Republic. Given the seismic hazard presented by this earthquake activity it is critical to perform systematic and continuous studies aimed at understanding and mitigating the impacts of earthquakes. The major effects to a site are due to seismic wave amplification at specific frequencies caused by local unconsolidated sediments during strong ground motions. Therefore, it is important to recognize and mitigate these. The Puerto Rico Seismic Network (PRSN) at the University of Puerto Rico, Mayagüez (Recinto Universitario de Mayagüez [RUM]) and the Puerto Rico Strong Motion Program (PRSMP), in collaboration with the United States Geological Survey (USGS) are conducting a passive-source seismic experiment to investigate the potential for seismic amplification by soils in Mayagüez, Puerto Rico. The goal of this experiment is to quantify the potential soil amplification in Mayagüez, which is located in the western portion of the island. This region experienced significant damage from shaking in the 1918, 7.3 Mw earthquake offshore of western Puerto Rico, making it a prime target for a pilot study to examine soil amplification. Local soil and bedrock conditions in Mayagüez are similar to other areas of the Caribbean, so results will have implications throughout the region. For this study, eleven L-22 sensors with Reftek RT130 recorders were installed in April 2019 to collect data for a period of six months. Since this time, there have been sixty-one M3 or greater earthquakes in the region per month and six M6.5 or greater teleseisms that should provide data suitable for analysis. Data are currently being analyzed using simple spectral ratios of soil sites to bedrock sites. We will present information about the deployment, experiment goals, and preliminary results. The results of this experiment will provide data to refine future hazard mapping and ground motion models of the island.

The Eastern Mediterranean Basin (EMB) is under the threat of tsunami events triggered by various causes including earthquakes and landslides. We propose a deployment of Offshore Bottom Pressure Gauges (OBPGs) around Crete Island, which would enable tsunami early warning by data assimilation for disaster mitigation. Our OBPG network consists of 12 gauges distributed around Crete Island. The locations of OBPGs are confirmed by Empirical Orthogonal Function (EOF) analysis of the pre-calculated tsunami scenarios, and most of them are placed at the locations where the most energetic wave dynamics occur. We demonstrate three test cases comprising a hypothetical seismogenic tsunami in east Sicily, a hypothetical landslide tsunami in the Aegean Sea, and the real tsunami event of the May 2020 off the Crete earthquake. Our designed OBPG network achieves a forecasting accuracy of 88.5 % for the hypothetical seismogenic tsunami and 85.3% for the hypothetical landslide tsunami with warning lead times of 10-20 min for both cases. For the real event of May 2020, it predicts the tsunami arrival at tide gauge NOA-04 accurately; the observed and forecasted amplitudes of the first wave are 5.0 cm and 4.5 cm, respectively. The warning lead time for the May 2020 event was ~10 min. Therefore, our results reveal that the assimilation of OBPG data can satisfactorily forecast the amplitudes and arrival times for tsunamis in the EMB. We note that further studies are necessary to examine the relation between the performance of the system and the number of OBPGs or the tsunami characteristics.

We present observations on a new precursory phase of seismic waves scattered in the deep Earth. This phase arrives prior to the PKPab wave at epicentral distances larger than 155º, and we call it PKPab precursor. We show that the presence of the PKPab precursor is a necessary consequence of scattering in D’‘, which is the commonly accepted cause of the PKPdf precursor at distances smaller than 145º. PKPdf waves that propagate through the inner core should arrive before the PKPab precursor but those, are strongly attenuated in the inner core at frequencies between 4 Hz and 8 Hz used here, making the PKPab precursor the earliest teleseismic signal at distances larger than 155º. Calculated PKPab precursor sensitivity kernel shows that this phase is mostly sensitive to scattering along the closest PKPbc path between source and receiver. It can thus help to constrain the lateral distribution of heterogeneity along D”.

Mesoscale ocean eddies dramatically impact oceanic material transport, momentum and energy budgets, and large-scale ocean circulation; therefore, reasonably diagnosing their effects is crucial for providing insights into eddy parameterization scheme development. In this work, a Reynolds and coarse-graining hybrid eddy transport diagnostic framework is proposed and applied in the Southern Ocean. Both the isotropic transport coefficient and anisotropic transport tensor are diagnosed and decomposed into contributions from transient and stationary eddies. The tensor can be split into its symmetric and antisymmetric parts, and the symmetric tensor is further diagonalized to analyze the eigenvalues and eigenvectors. We verify that the anisotropic assumption better fits the ocean mesoscale eddy transport process than the isotropic assumption, at least in the Southern Ocean. We place particular emphasis on the transport tensor’s stationary component affected by large-scale topographies, nonconservative processes, and large-scale flow structures and find that its influence is highly anisotropic horizontally and varies vertically. We probe all tensor-related elements that emerge in our hybrid framework, especially the eigenvalues and eigenvectors of the symmetric tensor. We reveal all three configurations of the major and minor eigenvalues that appear in the Southern Ocean, where the one representing vortex filamentation is the most common scenario. In addition, we discover a high randomness of the eigenvectors, which implies the possibility of a semideterministic and semistochastic anisotropic parameterization scheme.

Regional geodynamics studies of the eastern United States (e.g., Ghosh et al., 2019) have shed light on the force balance controlling intraplate, passive margin seismicity. Recent observations of crustal structure in the Southeastern United States (Chen et al., 2018; Hopper et al., 2016; Parker et al., 2016; Savage et al., 2017; Wagner et al., 2018) now allow us to examine the gravitational component of force balance in more detail. Here, we examine the role of gravitational potential energy (GPE) within the crust and upper mantle in ongoing stress, strain, and tectonism in the Southeastern United States. We first calculate GPE differences using density and crustal thickness data from Crust 1.0 (Laske et al., 2013) which are integrated over the thickness of the lithosphere on a 0.5 by 0.5 degree grid (e.g., Flesch et al., 2001). In further models we modify crustal densities using recent seismic observations (e.g., Parker et al., 2016; Wagner et al., 2018). We compare model results to earthquake epicenters and locations of inherited structures within our study area, including the Reelfoot Rift; New Madrid Seismic Zone; Illinois Basin; New York-Alabama Lineament; sutures between sections of accreted terrane; and a region of high seismic velocity beneath central West Virginia interpreted as delaminated, eclogitized crust (Biryol et al., 2016). Whereas in most locations seismicity is associated with higher magnitudes of GPE, inherited structures may explain regions in which earthquakes occur in areas with lower magnitudes of GPE.

The Magnetic Pileup Boundary or Induced Magnetosphere Boundary (IMB) has been an enigma in Mars aeronomy. Previously dubbed the planetopause, magnetopause, ion-composition boundary, and protonopause, identification of this unique plasma region has been marked by difficulty. In this case study, we used data from the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission to identify IMB crossings and configurations during the month of September 2017 with a particular focus on the 10 September 2017 solar events. It was concluded that the ICME had no statistically significant impact on the IMB standoff locations. This study also investigated the effects of upstream dynamic pressure, thermal pressure from the magnetosheath, magnetic pressure from the Magnetic Pileup Region (MPR), thermal pressure associated with the ionosphere, and Extreme Ultraviolet (EUV) irradiance on the IMB during September 2017. We have found that during the 163 IMB crossings, magnetic pressure in the MPR and thermal pressure in the ionosphere had the largest influence on the IMB standoff distance.

Dust particles are effective ice nuclei and are known to affect precipitation. Here, the possible impacts of mineral dusts on summertime cloud and precipitation over the Taiwan region are investigated through analysis of 25 years (1989 – 2013) of multiple observational and modeling datasets. Due to the unique mechanism, typhoon precipitations are excluded in this study. Statistical methods are used to untangle the influences of dust from the co-varying water vapor conditions. The results suggest a statistically significant positive correlation between non-typhoon precipitation and number concentration of dust particles larger than 0.5 µm () in July and August in the regions with heavy precipitation. From clean (0.008 cm) to dusty days (0.2 cm), averaged ice (liquid) water paths and precipitation increase by ~25% (~20%) and ~70% over the orographic region, and vertically, ~30% more cloud ice content is generated at ~ 350 hPa (T = ~−20℃), enhancing the development of the mixed-phase cloud and precipitation. The results also indicate critical role of the atmospheric water vapor in the responses of precipitation to , with precipitation increasing more significantly with in higher water vapor circumstances.

We report on the local structure of the Martian subsolar Magnetic Pileup Boundary (MPB) from minimum variance analysis of the magnetic field measured by the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft for six orbits. In particular, we detect a well defined current layer within the MPB’s fine structure and provide a local estimate of its current density which results in a sunward Lorentz force. This force accounts for the deflection of the solar wind ions and the acceleration of electrons which carry the interplanetary magnetic field through the MPB into the Magnetic Pileup Region. We find that the thickness of the MPB current layer is of the order of both the upstream (magnetosheath) solar wind proton inertial length and convective gyroradius. This study provides a high resolution view of one of the components of the current system around Mars reported in recent works.

Currently, the most popular approach for assessing the tsunami hazard on a coast is the PTHA (Probabilistic Tsunami Hazard Assessment). In this study, we develop one of the variants of the SPTHA (Seismic PTHA) method, adapted to solving near-field tsunami zoning problems. The approach is applied to assessing the tsunami hazard of the Bechevinskaya Cove located on the eastern coast of the Kamchatka Peninsula in the northern part of Avachinsky Bay. We propose the method, algorithms and results of probabilistic assessment of the cove’s tsunami hazard in order to determine the safest water areas, in which the values of the intensity measures (IMs) of tsunami will not exceed the specified threshold values with the given recurrence rates. The method includes analysis of seismotectonics of the region, construction of a catalog of model tsunamigenic earthquakes, determination of their statistical characteristics, scenario numerical modeling of the dynamics of tsunami waves, calculations of the values of IMs that can be exceeded with the given recurrence rates (on average 1 time in 100, 500, 1000 years). Spatial distributions of the maximum wave heights and maximum velocities are provided for the recurrence rates. Three configurations of the water area are considered, including the possibility of constructing protective structures, and conclusions are drawn about their influence on the tsunami hazard assessments in the cove. 1. Introduction The problem of tsunami zoning, which consists in the quantitative classification of the coast and adjacent aquatory by the degree of tsunami hazard, is one of the classic tsunami problems and requires the use of multidisciplinary tools and methods for its solution (Gusiakov, 2017). Hereinafter, tsunami hazard is the degree (level) of exposure of water areas and coasts to the tsunami threat in terms of measuring the catastrophic wave intensity. One of the first approaches to solving the problem of tsunami zoning was a method based on the use of historical data, materials from modern instrumental observations, as well as geological studies of paleo-tsunami along the coastal areas. The main limitation of the “historical” approach is a short series of observations. For near-field tsunami zoning problems the number of such observations is usually objectively limited by the short historical period of observations and the preservation of tsunami deposits, which also limits the accuracy of statistical estimates of tsunami hazard. Scenario modeling is an alternative based on estimates of the statistical properties of tsunami sources and the results of simulation (mathematical modeling) of the transformation of tsunami waves from the source to the coast. This approach uses a series of model tsunamigenic events of arbitrary length and thus clarifies probabilistic estimates of tsunami hazard. One of the ways to use the results of scenario calculations to solve the problem of tsunami zoning is to determine the extreme (worst case)